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1.  Skin sympathetic nerve activity in humans during exposure to emotionally-charged images: sex differences 
While it is known that anxiety or emotional arousal affects skin sympathetic nerve activity (SSNA), the galvanic skin response (GSR) is the most widely used parameter to infer increases in SSNA during stress or emotional studies. We recently showed that SSNA provides a more sensitive measure of emotional state than effector-organ responses. The aim of the present study was to assess whether there are gender differences in the responses of SSNA and other physiological parameters such as blood pressure, heart rate, skin blood flow and sweat release, while subjects viewed neutral or emotionally-charged images from the International Affective Picture System (IAPS). Changes in SSNA were assessed using microneurography in 20 subjects (10 male and 10 female). Blocks of positively-charged (erotica) or negatively-charge images (mutilation) were presented in a quasi-random fashion, following a block of neutral images, with each block containing 15 images and lasting 2 min. Images of both erotica and mutilation caused significant increases in SSNA, with increases being greater for males viewing erotica and greater for females viewing mutilation. The increases in SSNA were often coupled with sweat release and cutaneous vasoconstriction; however, these markers were not significantly different than those produced by viewing neutral images and were not always consistent with the SSNA increases. We conclude that SSNA increases with both positively-charged and negatively-charged emotional images, yet sex differences are present.
PMCID: PMC3958733  PMID: 24678303
skin sympathetic nerve activity; emotional processing; sex differences; sweat release; microneurography
2.  Mental stress elicits sustained and reproducible increases in skin sympathetic nerve activity 
Physiological Reports  2013;1(1):e00002.
Mental stress (MS) is a known trigger of myocardial infarction and sudden death. By activating the sympathetic nervous system, MS may have deleterious effect on the cardiovascular system but this process is not completely understood. The primary aim of this study was to quantify the effect of MS on skin sympathetic nerve activity (SSNA). The secondary aim was to determine the reproducibility of SSNA to MS within a given day and ∼1 week later. Ten subjects (26 ± 1 year) performed two bouts of mental arithmetic lasting 3 min. The bouts were separated by 45 min. One week later the subjects returned to repeat MS. All experiments were conducted in the supine posture during the morning hours. To maintain neutral skin temperature, each subject wore a custom suit (34–35°C). Skin blood flow and sweat rate were measured on the dorsal foot. MS elicited a marked increase in SSNA within the first 10 sec (184 ± 42%; P < 0.01) in all subjects, which was less during the remaining period of MS, but remained elevated (87 ± 20; P < 0.01). The pattern of responses to MS was unchanged during the second bout (10 sec, 247 ± 55%; 3 min average, 133 ± 29%) and during the retest 1 week later (10 sec, 196 ± 55%; 3 min average, 117 ± 36%). MS did not significantly affect cutaneous vascular conductance or sweat rate during any trial. In summary, MS elicits robust and reproducible increases in SSNA in humans, which may be followed over time to observe alterations in the regulation of the autonomic nervous system.
PMCID: PMC3673729  PMID: 23750321
Blood pressure; heart rate; psychosocial stress; reproducibility of results
3.  Mental Stress Elicits Sustained and Reproducible Increases in Skin Sympathetic Nerve Activity 
Physiological reports  2013;1(1):e00002.
Mental stress (MS) is a known trigger of myocardial infarction and sudden death. By activating the sympathetic nervous system, MS may have deleterious effect on the cardiovascular system but this process is not completely understood. The primary aim of this study was to quantify the effect of MS on skin sympathetic nerve activity (SSNA). The secondary aim was to determine the reproducibility of SSNA to MS within a given day and ~1 week later. Ten subjects (26±1 yr.) performed two bouts of mental arithmetic lasting 3 min. The bouts were separated by 45 min. One week later the subjects returned to repeat MS. All experiments were conducted in the supine posture during the morning hours. To maintain neutral skin temperature, each subject wore a custom suit (34-35°C). Skin blood flow and sweat rate were measured on the dorsal foot. MS elicited a marked increase in SSNA within the first 10 s (184±42%; P<0.01) in all subjects, which was less during the remaining period of MS but remained elevated (87±20; P<0.01). The pattern of responses to MS was unchanged during the second bout (10 s, 247±55%; 3 min avg., 133±29%) and during the retest 1 week later (10 s, 196±55%; 3 min avg., 117±36%). MS did not significantly affect cutaneous vascular conductance or sweat rate during any trial. In summary, MS elicits robust and reproducible increases in SSNA in humans which may be followed over time to observe alterations in the regulation of the autonomic nervous system.
PMCID: PMC3673729  PMID: 23750321
blood pressure; heart rate; psychosocial stress; reproducibility of results
4.  Cutaneous sympathetic neural responses to body cooling in type 2 diabetes mellitus 
In humans, sympathetic vasoconstrictor nerves in the skin contribute to resting vascular tone and mediate reflex vasoconstrictor responses to body cooling. Although it is well recognized that type 2 diabetes mellitus (T2DM) is associated with peripheral neurovascular changes, it is unclear to what extent the thermal responsiveness of the cutaneous vasoconstrictor system is altered in individuals with relatively uncomplicated T2DM. We tested the hypothesis that skin sympathetic nerve activity (SSNA) is decreased at baseline and during body cooling in individuals with T2DM compared to healthy controls (C) of similar age and body size. We measured SSNA (microneurography) and skin blood flow (laser-Doppler flowmetry) in the innervated area in 8 T2DM and 12 C subjects at baseline and during 3–4 minutes of rapid whole body cooling via water-perfused suit. SSNA (total integrated activity) increased, and cutaneous vascular conductance decreased in both groups during body cooling (P < 0.01 for both). However, SSNA was not different between groups during either baseline or body cooling conditions (P = NS). The deltas in SSNA between baseline and body cooling were similar between groups: T2DM: 55 ± 27 and C: 57 ± 12 units (P = NS). We conclude that reflex cutaneous sympathetic and vascular responses to rapid whole body cooling are preserved in relatively healthy individuals with T2DM.
PMCID: PMC2982880  PMID: 20659817
skin sympathetic nerve activity; thermoregulation; skin blood flow; vasoconstriction
5.  Chronic Heart Failure Does Not Attenuate the Total Activity of Sympathetic Outflow to Skin During Whole Body Heating 
Circulation. Heart failure  2013;6(2):271-278.
Previous studies show that the rise in skin blood flow and cutaneous vascular conductance (CVC) during heat stress is substantially attenuated in chronic heart failure (CHF) patients. The mechanism(s) responsible for this finding is not clear. In particular, little is known regarding the responses of skin sympathetic nerve activity (SSNA) that control the skin blood flow during heat stress in CHF patients. We examined the effects of a modest heat stress to test the hypothesis that SSNA responses could be attenuated in CHF.
Methods and Results
We assessed SSNA (microneurography) from the peroneal nerve and skin blood flow (forearm laser Doppler) in 9 patients with stable class II-III CHF and in matched healthy subjects during passive whole body heating with a water perfused suit. Whole body heating induced similar increases in internal temperature (~0.6 °C) in both groups. Whole body heat stress evoked similar SSNA activation in CHF patients (Δ891±110 units/min) and the control subjects (Δ787±84 units/min, P=0.66), while the elevation in forearm CVC in patients with CHF was significantly lower than that in healthy control subjects (Δ131±29 vs. Δ623±131%, P=0.001).
The present data show that SSNA activation during a modest whole body heat stress is not attenuated in CHF. Thus, the attenuated skin vasodilator response in CHF patients is not due to a reduction in total activity of sympathetic outflow to skin.
PMCID: PMC3738175  PMID: 23395933
autonomic; regional blood flow; vasodilation; heart failure
6.  Skin sympathetic nerve activity in Guillain-Barré syndrome: a microneurographic study 
To assess autonomic dysfunction, skin sympathetic nerve activity (SSNA) of four patients with Guillain-Barré syndrome was microneurographically studied in the acute and remission phase. Autonomic symptoms such as sinus tachycardia, palmar hyperhidrosis, hypertension, and orthostatic hypotension were present in the acute phase, but all subsided during remission. Basal resting SSNA and the responses to various physical and mental stimuli were all increased in the acute phase and returned almost to normal during remission. Rate of response in sweat rate and blood flow against SSNA were kept proportionally constant during both the acute and remission phases. These findings suggest that some autonomic nerve symptoms of Guillain-Barré syndrome, particularly during the acute phase, are due to increased SSNA.

PMCID: PMC2169766  PMID: 9343142
7.  Leptin acts in the forebrain to differentially influence baroreflex control of lumbar, renal and splanchnic sympathetic nerve activity and heart rate 
Hypertension  2013;61(4):10.1161/HYPERTENSIONAHA.111.00518.
While leptin is known to increase sympathetic nerve activity (SNA), we tested the hypothesis that leptin also enhances baroreflex control of SNA and HR. Using α-chloralose anesthetized male rats, mean arterial pressure (MAP), HR, lumbar SNA (LSNA), splanchnic SNA (SSNA), and renal SNA (RSNA) were recorded before and for 2 hr after lateral cerebroventricular (LV) leptin or aCSF administration. Baroreflex function was assessed using a four parameter sigmoidal fit of HR and SNA responses to slow ramp (3-5 min) changes in MAP, induced by iv infusion of nitroprusside and phenylephrine. Leptin (3 μg) increased (P<0.05) basal LSNA, SSNA, RSNA, HR and MAP, and the LSNA, SSNA, RSNA, and HR baroreflex maxima. Leptin also increased gain of baroreflex control of LSNA and RSNA, but not of SSNA or HR. The elevations in HR were eliminated by pretreatment with methscopalamine, to block parasympathetic nerve activity; however, after cardiac sympathetic blockade with atenolol, leptin still increased basal HR and MAP and the HR baroreflex maximum and minimum. Leptin (1.5 μg) also increased LSNA and enhanced LSNA baroreflex gain and maximum, but did not alter MAP, HR, or the HR baroreflex. LV aCSF had no effects. Finally, to test if leptin acts in the brainstem, leptin (3 μg) was infused into the 4th ventricle; however, no significant changes were observed. In conclusion, leptin acts in the forebrain to differentially influence baroreflex control of LSNA, RSNA, SSNA and HR, with the latter action mediated via suppression of parasympathetic nerve activity.
PMCID: PMC3823577  PMID: 23424232
male rats; RSNA; LSNA; SSNA; methscopolamine; parasympathetic
8.  Emotional modulation of pain and spinal nociception in persons with major depressive disorder (MDD) 
Pain  2013;154(12):10.1016/j.pain.2013.08.009.
Major depressive disorder (MDD) is associated with risk for chronic pain, but the mechanisms contributing to the MDD and pain relationship are unclear. To examine whether disrupted emotional modulation of pain might contribute, this study assessed emotional processing and emotional modulation of pain in healthy controls and unmedicated persons with MDD (14 MDD, 14 controls). Emotionally-charged pictures (erotica, neutral, mutilation) were presented in four blocks. Two blocks assessed physiological-emotional reactions (pleasure/arousal ratings, corrugator EMG, startle modulation, skin conductance) in the absence of pain and two blocks assessed emotional modulation of pain and the nociceptive flexion reflex (NFR, a physiological measure of spinal nociception) evoked by suprathreshold electric stimulations. Results indicated pictures generally evoked the intended emotional responses; erotic pictures elicited pleasure, subjective arousal, and smaller startle magnitudes, whereas mutilation pictures elicited displeasure, corrugator EMG activation, and subjective/physiological arousal. However, emotional processing was partially disrupted in MDD as evidenced by a blunted pleasure response to erotica and a failure to modulate startle according to a valence linear trend. Furthermore, emotional modulation of pain was observed in controls, but not MDD, even though there were no group differences in NFR threshold or emotional modulation of NFR. Together, these results suggest supraspinal processes associated with emotion processing and emotional modulation of pain may be disrupted in MDD, but brain-to-spinal cord processes that modulate spinal nociception are intact. Thus, emotional modulation of pain deficits may be a phenotypic marker for future pain risk in MDD.
PMCID: PMC3844118  PMID: 23954763
major depressive disorder; pain modulation; RIII reflex; affective processing; psychophysiology; supraspinal processing
9.  Sympathetic nerve activity can be estimated from skin conductance responses — A comment on Henderson et al. (2012)☆ 
Neuroimage  2014;84(100):122-123.
A recent paper by Henderson et al. (2012) claimed that skin sympathetic nerve activity (SSNA) can not be retrieved from skin conductance responses (SCR). Here, I argue that this claim is not supported by the literature, and comment on contemporary approaches of estimating SSNA from SCR using biophysical models.
•Sympathetic arousal can be estimated from skin conductance responses (SCR).•Such estimation relies on estimation of skin sympathetic nerve activity (SSNA).•Physiological work has established a linear relationship of SCR and SSNA amplitudes.
PMCID: PMC3898862  PMID: 23994456
Skin conductance responses; Skin sympathetic nerve activity; Electrodermal activity; Galvanic skin response; GSR; EDA; SCR; SSNA; Sympathetic arousal; Mathematical model; Biophysical model
10.  Emotional modulation of pain and spinal nociception in fibromyalgia 
Pain  2013;154(7):1045-1056.
Fibromyalgia (FM) is characterized by widespread pain, as well as affective disturbance (e.g., depression). Given that emotional processes are known to modulate pain, a disruption of emotion and emotional modulation of pain and nociception may contribute to FM. The present study used a well-validated affective picture-viewing paradigm to study emotional processing and emotional modulation of pain and spinal nociception. Participants were 18 individuals with FM, 18 individuals with rheumatoid arthritis (RA), and 19 healthy pain-free controls (HC). Mutilation, neutral, and erotic pictures were presented in four blocks; two blocks assessed only physiological-emotional reactions (i.e., pleasure/arousal ratings, corrugator EMG, startle modulation, skin conductance) in the absence of pain and two blocks assessed emotional reactivity and emotional modulation of pain and the nociceptive flexion reflex (NFR, a physiological measure of spinal nociception) evoked by suprathreshold electric stimulations over the sural nerve. In general, mutilation pictures elicited displeasure, corrugator activity, subjective arousal, and sympathetic activation, whereas erotic pictures elicited pleasure, subjective arousal, and sympathetic activation. However, FM was associated with deficits in appetitive activation (e.g., reduced pleasure/arousal to erotica). Moreover, emotional modulation of pain was observed in HC and RA, but not FM, even though all three groups evidenced modulation of NFR. Additionally, NFR thresholds were not lower in the FM group, indicating a lack of spinal sensitization. Together, these results suggest that FM is associated with a disruption of supraspinal processes associated with positive affect and emotional modulation of pain, but not brain-to-spinal cord circuitry that modulates spinal nociceptive processes.
PMCID: PMC3679206  PMID: 23622762
emotion; affect; electric stimulation; descending pain modulation; chronic pain; startle reflex
11.  Intrathecal orexin A increases sympathetic outflow and respiratory drive, enhances baroreflex sensitivity and blocks the somato-sympathetic reflex 
British Journal of Pharmacology  2011;162(4):961-973.
Intrathecal (i.t.) injection of orexin A (OX-A) increases blood pressure and heart rate (HR), but the effects of OX-A on sympathetic and phrenic, nerve activity, and the baroreflex(es), somato-sympathetic and hypoxic chemoreflex(es) are unknown.
Urethane-anaesthetized, vagotomized and artificially ventilated male Sprague-Dawley rats were examined in this study. The effects of i.t. OX-A (20 nmol 10 µL−1) on cardiorespiratory parameters, and responses to stimulation of the sciatic nerve (electrical), arterial baroreceptors (phenylephrine hydrochloride, 0.01 mg kg−1 i.v.) and peripheral (hypoxia) chemoreceptors were also investigated.
i.t. OX-A caused a prolonged dose-dependent sympathoexcitation, pressor response and tachycardia. The peak effect was observed at 20 nmol with increases in mean arterial pressure, HR and splanchnic sympathetic nerve activity (sSNA) of 32 mmHg, 52 beats per minute and 100% from baseline respectively. OX-A also dose-dependently increased respiratory drive, as indicated by a rise in phrenic nerve amplitude and a fall in phrenic nerve frequency, an increase in neural minute ventilation, a lengthening of the expiratory period, and a shortening of the inspiratory period. All effects of OX-A (20 nmol) were attenuated by the orexin receptor 1 antagonist SB 334867. OX-A significantly reduced both sympathoexcitatory peaks of somato-sympathetic reflex while increasing baroreflex sensitivity. OX-A increased the amplitude of the pressor response and markedly amplified the effect of hypoxia on sSNA.
Thus, activation of OX receptors in rat spinal cord alters cardiorespiratory function and differentially modulates sympathetic reflexes.
PMCID: PMC3042205  PMID: 21054340
Orexin A; sympathetic nerve activity; phrenic nerve discharge; somato-sympathetic reflex; baroreflex; hypoxia
12.  Nucleic acid distribution pattern as a possible biomarker for metabolic activities of neoplastic cells: a digitally-aided fluorescence microscopy study on normal and neoplastic lymphocytes of acute and chronic canine lymphocytic leukemia 
Metabolic states of neoplastic cells are increasingly being relied upon for diagnostic and prognostic assessment of neoplastic conditions. The nucleic acid distribution pattern of cells in general, in terms of degree of condensation of the nuclear chromatin and overall spread of the nucleic acid within the nuclear and cytoplasmic compartments, can reflect the metabolic state of the cell. This simple but logical concept appears not be put into consideration to date as numerous attempts are being made towards formulating reliable biomarkers for rapid diagnosis, prognosis and subsequent therapeutic interventions for neoplastic conditions. We comparatively evaluated nucleic acid distribution patterns of normal lymphocytes and neoplastic cells of lymphocytic lineage, employing light and fluorescence microscopy procedures, as well as digital imaging analytical methods.
The results demonstrate distinctiveness in the pattern of nucleic acid distribution for the normal lymphocytes and three lymphocytic neoplastic cell-types of canine lymphocytic leukemia that are categorized as small, intermediate and large neoplastic lymphocytes. Variably-shaped cytoplasmic processes laden with single-stranded nucleic acids (SSNA) were observed for the small and intermediate-sized neoplastic lymphocytes, compared with large neoplastic lymphocytes and the normal lymphocytes; the latter two categories of cells being virtually devoid of similar processes. Prominent cytoplasmic and nuclear clumps of SSNA, indicative of a higher rate of metabolic activity, were also observed within the neoplastic cells compared with fewer and narrower SSNA of the normal cells.
The comparative relative increases of SSNA in cytoplasmic processes and other cellular areas of small and intermediate-sized neoplastic lymphocytes is reflective of greater metabolic activity in neoplastic cells in general compared with their normal cellular counterparts.
PMCID: PMC2694150  PMID: 19432993
13.  Investigation of a Novel DNase of Streptococcus suis Serotype 2†  
Infection and Immunity  2004;72(2):774-781.
A secreted nuclease, SsnA, was identified in the virulent Streptococcus suis isolate SX332 and subsequently in each of the type strains of capsular serotypes 1 through 9. Screening of 258 porcine clinical isolates from surface (nasal mucosa or palatine tonsil) or internal (joint, brain or other internal organ) locations revealed a significant relationship (P < 0.001) between expression of nuclease and isolation from an internal site. A 3,126-bp gene, ssnA, was identified from a phenotypically nuclease-negative pGh9:ISS1 insertion mutant, and analysis of the predicted SsnA sequence revealed a 35-amino-acid (aa) secretion signal sequence, a 22-aa DNA-binding domain, and a typical gram-positive cell wall sorting motif. A requirement of Ca2+ and Mg2+ for SsnA activity was determined, and the substrate specificity was found to be for single- and double-stranded linear DNA. Reverse transcription-PCR experiments revealed that ssnA is expressed throughout all stages of S. suis growth, and Western blots with porcine anti-S. suis immune sera against a recombinant, truncated SsnA derivative (rSsnAΔ) confirmed that SsnA is expressed in vivo. Furthermore, anti-rSsnAΔ antibodies were sufficient to neutralize SsnA activity. Analyses of subcellular fractions of SX332 and derived mutants, on DNA-containing polyacrylamide gels and by Western blotting, suggest that SsnA is cell wall located.
PMCID: PMC321577  PMID: 14742520
14.  Intrathecal neurotensin is hypotensive, sympathoinhibitory and enhances the baroreflex in anaesthetized rat 
British Journal of Pharmacology  2012;166(1):378-389.
The neuromodulatory effects of the gut-neuropeptide neurotensin on sympathetic vasomotor tone, central respiratory drive and adaptive reflexes in the spinal cord, are not known.
Neurotensin (0.5 µM–3 mM) was administered into the intrathecal (i.t.) space at the sixth thoracic spinal cord segment in urethane-anaesthetized, paralysed, vagotomized male Sprague–Dawley rats. Pulsatile arterial pressure, splanchnic sympathetic nerve activity (sSNA), phrenic nerve activity, ECG and end-tidal CO2 were recorded.
Neurotensin caused a dose-related hypotension, sympathoinhibition and bradycardia. The maximum effects were observed at 3000 µM, where the decreases in mean arterial pressure (MAP), heart rate (HR) and sSNA reached −25 mmHg, −26 beats min−1 and −26% from baseline, respectively. The sympathetic baroreflex was enhanced. Changes in central respiratory drive were characterized by a fall in the amplitude of the phrenic nerve activity. Finally, administration of SR 142948A (5 mM), a potent, selective antagonist at neurotensin receptors, caused a potent hypotension (−35 mmHg), bradycardia (−54 beats min−1) and sympathoinhibition (−44%). A reduction in the amplitude and frequency of the phrenic nerve activity was also observed.
The data demonstrate that neurotensin plays an important role in the regulation of spinal cardiovascular function, affecting both tone and adaptive reflexes.
PMCID: PMC3415662  PMID: 22035146
neurotensin; intrathecal; blood pressure; sympathetic nerve activity; baroreflex; SR 142948A; phrenic nerve activity
15.  Orexin A in rat rostral ventrolateral medulla is pressor, sympatho-excitatory, increases barosensitivity and attenuates the somato-sympathetic reflex 
British Journal of Pharmacology  2012;165(7):2292-2303.
The rostral ventrolateral medulla (RVLM) maintains sympathetic nerve activity (SNA), and integrates adaptive reflexes. Orexin A-immunoreactive neurones in the lateral hypothalamus project to the RVLM. Microinjection of orexin A into RVLM increases blood pressure and heart rate. However, the expression of orexin receptors, and effects of orexin A in the RVLM on splanchnic SNA (sSNA), respiration and adaptive reflexes are unknown.
The effect of orexin A on baseline cardio-respiratory variables as well as the somato-sympathetic, baroreceptor and chemoreceptor reflexes in RVLM were investigated in urethane-anaesthetized, vagotomized and artificially ventilated male Sprague-Dawley rats (n= 50). orexin A and its receptors were detected with fluorescence immunohistochemistry.
Tyrosine hydroxylase-immunoreactive neurones in the RVLM were frequently co-localized with orexin 1 (OX1) and orexin 2 (OX2) receptors and closely apposed to orexin A-immunoreactive terminals. Orexin A injected into the RVLM was pressor and sympatho-excitatory. Peak effects were observed at 50 pmol with increased mean arterial pressure (42 mmHg) and SNA (45%). Responses to orexin A (50 pmol) were attenuated by the OX1 receptor antagonist, SB334867, and reproduced by the OX2 receptor agonist, [Ala11, D-Leu15]orexin B. Orexin A attenuated the somato-sympathetic reflex but increased baroreflex sensitivity. Orexin A increased or reduced sympatho-excitation following hypoxia or hypercapnia respectively.
Although central cardio-respiratory control mechanisms at rest do not rely on orexin, responses to adaptive stimuli are dramatically affected by the functional state of orexin receptors.
PMCID: PMC3413863  PMID: 21951179
orexin A; sympathetic vasomotor tone; somato-sympathetic reflex; baroreflex; chemoreflex
16.  Cannabinoid receptor activation in the rostral ventrolateral medulla oblongata evokes cardiorespiratory effects in anaesthetised rats 
British Journal of Pharmacology  2003;140(2):384-394.
The nature of the cardiorespiratory effects mediated by cannabinoids in the hindbrain is poorly understood. In the present study we investigated whether cannabinoid receptor activation in the rostral ventrolateral medulla oblongata (RVLM) affects cardiovascular and/or respiratory function.Initially, we looked for evidence of CB1 receptor gene expression in rostral and caudal sections of the rat ventrolateral medulla (VLM) using reverse transcription–polymerase chain reaction. Second, the potent cannabinoid receptor agonists WIN55,212-2 (0.05, 0.5 or 5 pmol per 50 nl) and HU-210 (0.5 pmol per 50 nl) or the CB1 receptor antagonist/inverse agonist AM281 (1 pmol per 100 nl) were microinjected into the RVLM of urethane-anaesthetised, immobilised and mechanically ventilated male Sprague–Dawley rats (n=22). Changes in splanchnic nerve activity (sSNA), phrenic nerve activity (PNA), mean arterial pressure (MAP) and heart rate (HR) in response to cannabinoid administration were recorded.The CB1 receptor gene was expressed throughout the VLM. Unilateral microinjection of WIN55,212-2 into the RVLM evoked short-latency, dose-dependent increases in sSNA (0.5 pmol; 175±8%, n=5) and MAP (0.5 pmol; 26±3%, n=8) and abolished PNA (0.5 pmol; duration of apnoea: 5.4±0.4 s, n=8), with little change in HR (P<0.005). HU-210, structurally related to Δ9-tetrahydrocannabinol (THC), evoked similar effects when microinjected into the RVLM (n=4). Surprisingly, prior microinjection of AM281 produced agonist-like effects, as well as significantly attenuated the response to subsequent injection of WIN55,212-2 (0.5 pmol, n=4).The present study reveals CB1 receptor gene expression in the rat VLM and demonstrates sympathoexcitation, hypertension and respiratory inhibition in response to RVLM-administered cannabinoids. These findings suggest a novel link between CB1 receptors in this region of the hindbrain and the central cardiorespiratory effects of cannabinoids. The extent to which these central effects contribute to the cardiovascular and respiratory outcomes of cannabis use remains to be investigated.
PMCID: PMC1574023  PMID: 12970095
Cannabinoid; CB1; cardiorespiratory; sympathoexcitation; apnoea; rostral ventrolateral medulla
17.  Mechanisms of cutaneous vasodilation during the postmenopausal hot flash 
Menopause (New York, N.Y.)  2011;18(4):359-365.
Menopausal hot flashes can seriously disrupt the lives of symptomatic women. The physiological mechanisms of the hot flash efferent responses, particularly in the cutaneous circulation, are not completely understood. The aim of this study was to examine the mechanisms of increases in skin blood flow during the postmenopausal hot flash in symptomatic women.
Healthy postmenopausal women rested in a temperature controlled laboratory while responses prior to and during hot flashes were recorded for three unique protocols. Protocols 1 and 2: Women were locally pretreated with an intradermal injection of botulinum toxin A (BTX; blocks the release of neurotransmitters from sympathetic cholinergic nerves) in the forearm (protocol 1) and in the glabellar region (protocol 2). Protocol 3: Skin sympathetic nerve activity from the peroneal nerve was recorded, along with skin blood flow and sweating within the region innervated by that neural signal. Skin blood flow was indexed using laser-Doppler flowmetry at BTX-treated and adjacent untreated control sites. The onset of a hot flash was objectively identified as a transient and pronounced elevation of sternal sweat rate.
The elevation in forearm (protocol 1) and glabellar skin blood flow (protocol 2) during hot flashes were attenuated at BTX sites relative to adjacent untreated sites (P<0.05 for both protocols). In protocol 3, skin sympathetic nerve activity significantly increased during hot flashes and returned to pre-flash levels following the hot flashes.
Elevations in skin blood flow during the postmenopausal hot flash are neurally mediated primarily through BTX sensitive nerves; presumably sympathetic cholinergic.
PMCID: PMC3117955  PMID: 21107299
Skin Blood Flow; Sympathetic Cholinergic; Menopause
18.  Emotional modulation of pain and spinal nociception in persons with severe insomnia symptoms 
Impaired sleep enhances pain, perhaps by disrupting pain modulation.
Given that emotion modulates pain, the present study examined whether emotional modulation of pain and nociception is impaired in persons with severe insomnia symptoms relative to controls.
Insomnia group (n=12) met ICD-10 symptoms for primary insomnia and controls (n=13) reported no sleep impairment. Participants were shown emotionally-evocative pictures (mutilation, neutral, erotica) during which suprathreshold pain stimuli were delivered to evoke pain and the nociceptive flexion reflex (NFR; physiological correlate of spinal nociception).
Emotional responses to pictures were similar in both groups, except that subjective valence/pleasure ratings were blunted in insomnia. Emotional modulation of pain and NFR was observed in controls, but only emotional modulation of NFR was observed in insomnia.
Consistent with previous findings, pain modulation is disrupted in insomnia which might promote pain. This may stem from disrupted supraspinal circuits not disrupted brain-to-spinal cord circuits.
PMCID: PMC3980198  PMID: 24101292
insomnia; pain modulation; sleep; psychophysiology; descending modulation; affect
19.  Psychophysical correlates of phantom limb experience. 
Phantom limb phenomena were correlated with psychophysiological measures of peripheral sympathetic nervous system activity measured at the amputation stump and contralateral limb. Amputees were assigned to one of three groups depending on whether they reported phantom limb pain, non-painful phantom limb sensations, or no phantom limb at all. Skin conductance and skin temperature were recorded continuously during two 30 minute sessions while subjects continuously monitored and rated the intensity of any phantom limb sensation or pain they experienced. The results from both sessions showed that mean skin temperature was significantly lower at the stump than the contralateral limb in the groups with phantom limb pain and non-painful phantom limb sensations, but not among subjects with no phantom limb at all. In addition, stump skin conductance responses correlated significantly with the intensity of non-painful phantom limb paresthesiae but not other qualities of sensation or pain. Between-limb measures of pressure sensitivity were not significantly different in any group. The results suggest that the presence of a phantom limb, whether painful or painless, is related to the sympathetic-efferent outflow of cutaneous vasoconstrictor fibres in the stump and stump neuromas. The hypothesis of a sympathetic-efferent somatic-afferent mechanism involving both sudomotor and vasoconstrictor fibres is proposed to explain the relationship between stump skin conductance responses and non-painful phantom limb paresthesiae. It is suggested that increases in the intensity of phantom limb paresthesiae follow bursts of sympathetic activity due to neurotransmitter release onto apposing sprouts of large diameter primary afferents located in stump neuromas, and decreases correspond to periods of relative sympathetic inactivity. The results of the study agree with recent suggestions that phantom limb pain is not a unitary syndrome, but a symptom class with each class subserved by different aetiological mechanisms.
PMCID: PMC1015107  PMID: 1402973
20.  Do brain responses to emotional images and cigarette cues differ? An fMRI study in smokers 
The European journal of neuroscience  2011;34(12):2054-2063.
Chronic smoking is thought to cause changes in brain reward systems that result in overvaluation of cigarette-related stimuli and undervaluation of natural rewards. We tested the hypotheses that, in smokers, brain circuits involved in emotional processing 1) would be more active during exposure to cigarette-related than neutral pictures, and 2) would be less active to pleasant compared to cigarette-related pictures, suggesting a devaluation of intrinsically pleasant stimuli. We obtained whole brain blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) data from 35 smokers during the presentation of pleasant (erotica and romance), unpleasant (mutilations and sad), neutral, and cigarette-related pictures. Whole brain analyses showed significantly larger BOLD responses during presentation of cigarette-related pictures relative to neutral ones within the secondary visual areas, the cingulate gyrus, the frontal gyrus, the dorsal striatum, and the left insula. BOLD responses to erotic pictures exceeded responses to cigarette-related pictures in all clusters except the insula. Within the left insula we observed larger BOLD responses to cigarette-related pictures than to all other picture categories. By including intrinsically pleasant and unpleasant pictures in addition to neutral ones, we were able to conclude that the presentation of cigarette-related pictures activates brain areas supporting emotional processes, but we did not find evidence of overall reduced activation of the brain reward systems in the presence of intrinsically pleasant stimuli.
PMCID: PMC3237919  PMID: 22097928
pictures; smoking; nicotine; emotions; insula
21.  Emotion and ocular responses in Parkinson’s Disease 
Neuropsychologia  2011;49(12):3247-3253.
Parkinson’s disease (PD) is a neurodegenerative disease that affects motor, cognitive, and emotional functioning. Previous studies reported reduced skin conductance responses in PD patients, compared to healthy older adults when viewing emotionally arousing pictures. Attenuated skin conductance changes in PD may reflect peripheral autonomic dysfunction (e.g., reduced nerve endings at the sweat gland) or, alternatively, a more central emotional deficit. The aim of the current study was to investigate a second measure of sympathetic arousal—change in pupil dilation. Eye movements, a motor-based correlate of emotional processing, were also assessed. Results indicated that pupil dilation was significantly greater when viewing emotional, compared to neutral pictures for both PD patients and controls. On the other hand, PD patients made fewer fixations with shorter scan paths, particularly when viewing pleasant pictures. These results suggest that PD patients show normal sympathetic arousal to affective stimuli (indexed by pupil diameter), but differences in motor correlates of emotion (eye movements.)
PMCID: PMC3384545  PMID: 21839756
emotion; arousal; Parkinson’s disease; pupil; eye movement
22.  Re-entrant Projections Modulate Visual Cortex in Affective Perception: Evidence From Granger Causality Analysis 
Human brain mapping  2009;30(2):532-540.
Re-entrant modulation of visual cortex has been suggested as a critical process for enhancing perception of emotionally arousing visual stimuli. This study explores how the time information inherent in large-scale electrocortical measures can be used to examine the functional relationships among the structures involved in emotional perception. Granger causality analysis was conducted on steady-state visual evoked potentials elicited by emotionally arousing pictures flickering at a rate of 10 Hz. This procedure allows one to examine the direction of neural connections. Participants viewed pictures that varied in emotional content, depicting people in neutral contexts, erotica, or interpersonal attack scenes. Results demonstrated increased coupling between visual and cortical areas when viewing emotionally arousing content. Specifically, intraparietal to inferotemporal and precuneus to calcarine connections were stronger for emotionally arousing picture content. Thus, we provide evidence for re-entrant signal flow during emotional perception, which originates from higher tiers and enters lower tiers of visual cortex.
PMCID: PMC3622724  PMID: 18095279
affective arousal; electroencephalography; emotion; Granger causality; steady-state potentials
23.  Effect of the Heat-exposure on Peripheral Sudomotor Activity Including the Density of Active Sweat Glands and Single Sweat Gland Output 
Tropical inhabitants are able to tolerate heat through permanent residence in hot and often humid tropical climates. The goal of this study was to clarify the peripheral mechanisms involved in thermal sweating pre and post exposure (heat-acclimatization over 10 days) by studying the sweating responses to acetylcholine (ACh), a primary neurotransmitter of sudomotor activity, in healthy subjects (n=12). Ten percent ACh was administered on the inner forearm skin for iontophoresis. Quantitative sudomotor axon reflex testing, after iontophoresis (2 mA for 5 min) with ACH, was performed to determine directly activated (DIR) and axon reflex-mediated (AXR) sweating during ACh iontophoresis. The sweat rate, activated sweat gland density, sweat gland output per single gland activated, as well as oral and skin temperature changes were measured. The post exposure activity had a short onset time (p<0.01), higher active sweat rate [(AXR (p<0.001) and DIR (p<0.001)], higher sweat output per gland (p<0.001) and higher transepidermal water loss (p<0.001) compared to the pre-exposure measurements. The activated sweat rate in the sudomotor activity increased the output for post-exposure compared to the pre-exposure measurements. The results suggested that post-exposure activity showed a higher active sweat gland output due to the combination of a higher AXR (DIR) sweat rate and a shorter onset time. Therefore, higher sudomotor responses to ACh receptors indicate accelerated sympathetic nerve responsiveness to ACh sensitivity by exposure to environmental conditions.
PMCID: PMC2997411  PMID: 21165324
Short-term heat-acclimatization; Sudomotor axon reflex; Active sweat gland; Single sweat gland output; Acetylcholine
24.  Quantitative measures of sympathetic skin response in diabetes: relation to sudomotor and neurological function. 
The sympathetic skin response (SSR) at the foot to a deep inspiration was measured in 68 randomly selected diabetic patients and 46 age matched normal subjects and compared with other quantitative measures of neurological and sudomotor function. SSR was obtained in all but three diabetic patients. The upper limit of normal for the onset latency was 2202 ms and the lower limit for the amplitude of the first wave 92 microV. Ten diabetic patients had measurable but prolonged latencies, and 11 had measurable but low amplitudes. There were no significant associations between latency, height, and age, but in insulin dependent patients there was a significant diminution of response amplitude with increasing duration of diabetes. Latency was weakly associated with Marstock thermal thresholds, respiratory RR variation, and common peroneal nerve conduction velocity. SSR amplitude was associated with the density of pilocarpine activatable sweatspots in the same region of the foot. Patients with abnormal latencies were significantly older and had reduced thermal sensation than those with normal latencies. Median coefficients of variation for repeat testing in diabetic patients were 9% for latency and 13% for amplitude. The test is objective and reproducible, but latency measurements reflect conduction in a long multineuronal pathway and are not purely a measure of peripheral C fibre function; amplitude measurements reflect the density of spontaneously activable sweat glands and are therefore a valid measure of peripheral sympathetic activity, though they depend more on temperature than do latencies (mean change over the range 32-34 degrees C; 8.5% degrees C for amplitude, -2.5%/degrees C for latency).
PMCID: PMC1015186  PMID: 1331334
25.  Effects of affective picture viewing on postural control 
BMC Neuroscience  2007;8:83.
Emotion theory holds that unpleasant events prime withdrawal actions, whereas pleasant events prime approach actions. Recent studies have suggested that passive viewing of emotion eliciting images results in postural adjustments, which become manifest as changes in body center of pressure (COP) trajectories. From those studies it appears that posture is modulated most when viewing pictures with negative valence. The present experiment was conducted to test the hypothesis that pictures with negative valence have a greater impact on postural control than neutral or positive ones. Thirty-four healthy subjects passively viewed a series of emotion eliciting images, while standing either in a bipedal or unipedal stance on a force plate. The images were adopted from the International Affective Picture System (IAPS). We analysed mean and variability of the COP and the length of the associated sway path as a function of emotion.
The mean position of the COP was unaffected by emotion, but unipedal stance resulted in overall greater body sway than bipedal stance. We found a modest effect of emotion on COP: viewing pictures of mutilation resulted in a smaller sway path, but only in unipedal stance. We obtained valence and arousal ratings of the images with an independent sample of viewers. These subjects rated the unpleasant images as significantly less pleasant than neutral images, and the pleasant images as significantly more pleasant than neutral images. However, the subjects rated the images as overall less pleasant and less arousing than viewers in a closely comparable American study, pointing to unknown differences in viewer characteristics.
Overall, viewing emotion eliciting images had little effect on body sway. Our finding of a reduction in sway path length when viewing pictures of mutilation was indicative of a freezing strategy, i.e. fear bradycardia. The results are consistent with current knowledge about the neuroanatomical organization of the emotion system and the neural control of behavior.
PMCID: PMC2082031  PMID: 17916245

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