Mutations in presenilin (PS) proteins cause familial Alzheimer’s disease. We herein tested the hypothesis that the expression levels of PS proteins are differentially affected during healthy aging, in the absence of pathological mutations. We used a preclinical model for aging to identify associations between PS expression and quantitative behavioral parameters for spatial memory and learning and motor coordination. We identified significant changes of PS protein expression in both cerebellum and forebrain that correlated with the performance in behavioral paradigms for motor coordination and memory and learning. Overall, PS1 levels were decreased, while PS2 levels were increased in aged mice compared with young controls. Our study presents novel evidence for the differential expression of PS proteins in a non-genetic model for aging, resulting in an overall increase of the PS2 to PS1 ratio. Our findings provide a novel mechanistic basis for molecular and functional changes during normal aging.
aging; behavior; neuron; cerebellum; cognitive performance; cognition; motor learning; behavior; neurodegeneration; calcium; Alzheimer’s disease
When synthetic cannabinoid compounds became controlled by state and federal governments, different, non-controlled compounds began to appear as marijuana substitutes. Unlike the scheduled cannabinoids, the newer compounds have not been characterized for potency and efficacy in preclinical studies. The purpose of these experiments was to determine whether some of the more recent synthetic compounds sold as marijuana substitutes have behavioral effects similar to those of Δ9-tetrahydrocannabinol (Δ9-THC), the pharmacologically active compound in marijuana. The compounds UR-144, XLR-11, AKB-48 (APINACA), PB-22 (QUPIC), 5F-PB-22 and AB-FUBINACA were tested for locomotor depressant effects in male Swiss-Webster mice and subsequently for their ability to substitute for Δ9-THC (3 mg/kg, i.p.) in drug discrimination experiments with male Sprague-Dawley rats. UR-144, XLR-11, AKB-48, and AB-FUBINACA each decreased locomotor activity for up to 90 min, whereas PB-22 and 5F-PB-22 produced depressant effects lasting 120-150 min. Each of the compounds fully substituted for the discriminative stimulus effects of Δ9-THC. These findings confirm the suggestion that these compounds have marijuana-like psychoactive effects and abuse liability.
cannabinoids; drug discrimination; locomotor activity; abuse liability; mouse; rat
Synthetic cathinones continue to be sold as “legal” alternatives to methamphetamine or cocaine. As these marginally legal compounds become controlled, suppliers move to other, unregulated compounds.
The purpose of these experiments was to determine whether several temporarily controlled cathinone compounds, which are currently abused on the street, stimulate motor activity and have discriminative stimulus effects similar to cocaine and/or methamphetamine.
Methcathinone, pentedrone, pentylone, 3-fluoromethcathinone (3-FMC), and 4-methylethcathinone (4-MEC) were tested for locomotor stimulant effects in mice and subsequently for substitution in rats trained to discriminate cocaine (10 mg/kg, i.p.) or methamphetamine (1 mg/kg, i.p.) from saline.
Methcathinone, pentedrone, and pentylone produced locomotor stimulant effects which lasted up to 6 hours. In addition, pentylone produced convulsions and lethality at 100 mg/kg. 4-MEC produced locomotor stimulant effects which lasted up to 2 hours. Methcathinone, pentedrone, pentylone, 3-FMC, and 4-MEC each produced discriminative stimulus effects similar to those of cocaine and methamphetamine.
All of the tested compounds produce discriminative stimulus effects similar to either those of cocaine, methamphetamine or both, which suggests that these compounds are likely to have similar abuse liability to cocaine and/or methamphetamine. Pentylone may be more dangerous on the street, as it produced adverse effects at doses that produced maximal stimulant-like effects.
cathinones; drug discrimination; locomotor activity; abuse liability; mouse; rat
Serotonin 5-HT2A and 5-HT2C receptors are thought to be the primary pharmacological mechanisms for serotonin-mediated hallucinogenic drugs, but recently there has been interest in metabotropic glutamate (mGluR2) receptors as contributors to the mechanism of hallucinogens.
The present study assesses the role of these 5-HT and glutamate receptors as molecular targets for two tryptamine hallucinogens, N,N-dimethyltryptamine (DMT) and N,N-diisopropyltryptamine (DiPT).
Drug discrimination, head twitch and radioligand binding assays were used. A 5-HT2AR inverse agonist (MDL100907), 5-HT2CR antagonist (SB242084) and mGluR2/3 agonist (LY379268) were tested for their ability to attenuate the discriminative stimulus effects of DMT and DiPT; an mGluR2/3 antagonist (LY341495) was tested for potentiation. MDL100907 was used to attenuate head twitches induced by DMT and DiPT. Radioligand binding studies and inosital-1-phosphate (IP-1) accumulation were performed at the 5-HT2CR for DiPT.
MDL100907 fully blocked the discriminative stimulus effects of DMT, but only partially blocked DiPT. SB242084 partially attenuated the discriminative stimulus effects of DiPT, but produced minimal attenuation of DMT’s effects. LY379268 produced potent, but only partial blockade of the discriminative stimulus effects of DMT. LY341495 facilitated DMT- and DiPT-like effects. Both compounds elicited head twitches (DiPT>DMT) which were blocked by MDL1000907. DiPT was a low potency full agonist at 5-HT2CR in vitro.
The 5-HT2AR likely plays a major role in mediating the effects of both compounds. 5-HT2C and mGluR2 receptors likely modulate the discriminative stimulus effects of both compounds to some degree.
N,N-Diisopropyltryptamine; N,N-Dimethyltryptamine; hallucinogens; drug discrimination; 5-HT2A; 5-HT2C; mGluR2; rat
A number of cannabinoid compounds are being sold in the form of incense as “legal” alternatives to marijuana. The purpose of these experiments was to determine whether the most common of these compounds have discriminative stimulus effects similar to Δ9-tetrahydrocannabinol, the main active component in marijuana. Locomotor depressant effects of JWH-018, JWH-073, JWH-200, JWH-203, JWH-250, AM-2201 and CP 47,497-C8-homolog were tested in mice. The compounds were then tested for substitution in rats trained to discriminate Δ9-tetrahydrocannabinol (3 mg/kg, i.p.). The time course of the peak dose of each compound was also tested. Each of the synthetic cannabinoids dose-dependently decreased locomotor activity for one to two hours. Each of the compounds fully substituted for the discriminative stimulus effects of Δ9-tetrahydrocannabinol, mostly at doses that produced only marginal amounts of rate suppression. JWH-250 and CP 47,497-C8-homolog suppressed response rates at doses that fully substituted for Δ9-THC. The time courses varied markedly between compounds. Most of the compounds had a shorter onset than Δ9-THC, and three lasted substantially longer (JWH-073, JWH-250 and CP 47,497-C8-homolog). Several of the most commonly used synthetic cannabinoids produce behavioral effects comparable to those of Δ9-tetrahydrocannabinol, which suggests that these compounds may share the psychoactive effects of marijuana responsible for abuse liability. The extremely long time course of the discriminative stimulus effects and adverse effects of CP 47,497-C8-homolog suggest that CP 47,497-C8-homolog may be associated with increased hazards in humans.
cannabinoids; drug discrimination; locomotor activity; abuse liability; mouse; rat
The purpose of this study was to determine if intake of the antioxidants coenzyme Q10 (CoQ10) or α-tocopherol (Toc), either alone or in combination, could ameliorate cognitive and psychomotor impairments of aged mice, as well as reduce oxidative burden in tissues. For a period of 10 weeks, male C57BL/6J mice (3 or 18 months) were fed either a control diet, or one of three diets supplemented with Toc, CoQ10 or their combination, and were tested for cognitive and psychomotor function. Old mice on the Toc or Toc/CoQ10 diets showed improved coordinated running performance. Mice on the diet containing Toc/CoQ10 demonstrated improved performance in the discriminated avoidance task. CoQ10 and Toc alone also resulted in improved performance, albeit to a lesser degree. Protein damage was decreased especially when the mice received Toc + CoQ10 combination. Overall, these results suggest that, Toc and CoQ supplementation can ameliorate age-related impairment and reduce protein oxidation. Moreover, concurrent supplementation of CoQ10 and Toc may be more effective than either antioxidant alone.
Behavior; antioxidants and mitochondria
Glaucoma is an optic neuropathy commonly associated with elevated intraocular pressure (IOP), leading to optic nerve head (ONH) cupping, axon loss, and apoptosis of retinal ganglion cells (RGCs), which could ultimately result in blindness. Brn3b is a class-4 POU domain transcription factor that plays a key role in RGC development, axon outgrowth, and pathfinding. Previous studies suggest that a decrease in Brn3b levels occurs in animal models of glaucoma. The goal of this study was to determine if adeno-associated virus (AAV)-directed overexpression of the Brn3b protein could have neuroprotective effects following elevated IOP-mediated neurodegeneration.
Intraocular pressure was elevated in one eye of Brown Norway rats (Rattus norvegicus), following which the IOP-elevated eyes were intravitreally injected with AAV constructs encoding either the GFP (rAAV-CMV-GFP and rAAV-hsyn-GFP) or Brn3b (rAAV-CMV-Brn3b and rAAV-hsyn-Brn3b). Retina sections through the ONH were stained for synaptic plasticity markers and neuroprotection was assessed by RGC counts and visual acuity tests.
Adeno-associated virus–mediated expression of the Brn3b protein in IOP-elevated rat eyes promoted an upregulation of growth associated protein-43 (GAP-43), actin binding LIM protein (abLIM) and acetylated α-tubulin (ac-Tuba) both posterior to the ONH and in RGCs. The RGC survival as well as axon integrity score were significantly improved in IOP-elevated rAAV-hsyn-Brn3b–injected rats compared with those of the IOP-elevated rAAV-hsyn-GFP– injected rats. Additionally, intravitreal rAAV-hsyn-Brn3b administration significantly restored the visual optomotor response in IOP-elevated rat eyes.
Adeno-associated virus–mediated Brn3b protein expression may be a suitable approach for promoting neuroprotection in animal models of glaucoma.
The POU domain transcription factor Brn3b has been shown to play a key role in the development of retinal ganglion cells. In the current study, adeno-associated virus–mediated Brn3b protein expression was shown to be neuroprotective in a rat model of ocular hypertension.
Brn3b; glaucoma; Morrison's model; neuroprotection; gene therapy
The main objective of this review is to provide an appraisal of the current status of the relationship between energy intake and the life span of animals. The concept, that a reduction in food intake, or caloric restriction (CR), retards the aging process, delays the age-associated decline in physiological fitness and extends the life span of organisms of diverse phylogenetic groups, is one of the leading paradigms in gerontology. However, emerging evidence disputes some of the primary tenets of this conception. One disparity is that the CR-related increase in longevity is not universal and may not even be shared among different strains of the same species. A further misgiving is that the control animals, fed ad-libitum (AL), become overweight, prone to early onset of diseases and death, and thus may not be the ideal control animals for studies concerned with comparisons of longevity. Re-examination of body weight and longevity data from a study involving over 60,000 mice and rats, conducted by a National Institute on Aging-sponsored project, suggests that CR-related increase in life span of specific genotypes is directly related to the gain in body weight under the AL feeding regimen. Additionally, CR in mammals and “dietary restriction” in organisms, such as Drosophila, are dissimilar phenomena, albeit they are often presented to be the very same. The latter involves a reduction in yeast rather than caloric intake, which is inconsistent with the notion of a common, conserved mechanism of CR action in different species. Although specific mechanisms by which CR affects longevity are not well understood, existing evidence supports the view that CR increases the life span of those particular genotypes that develop energy imbalance due to AL feeding. In such groups, CR lowers body temperature, rate of metabolism and oxidant production, and retards the age-related pro-oxidizing shift in the redox state.
Dietary restriction and aging; energy restriction and life span; oxidative stress and aging; free radicals and aging; mechanisms of aging; redox state and aging; caloric restriction and life span; redox stress hypothesis of aging
Phytoestrogens are plant-derived compounds found mainly in soy with known estrogenic properties and a potential for benefits to human health. Increased intake in phytoestrogens stemmed from the search for safe alternatives to hormone replacement therapies. Based on epidemiologic evidence comparing Western and Asian population and clinical studies, phytoestrogens show promise to improve health and brain function. This review will focus on the effects of phytoestrogens on cognition by examining clinical and animals studies, with special attention placed on (1) a window of therapeutic opportunity which may explains the discrepancy amongst studies, and (2) whether a sex/gender difference exists in response to phytoestrogen intake and what the possible underlying mechanisms may be.
Psychoactive substituted phenethylamines 2,5-dimethoxy-4-chlorophenethylamine (2C-C); 2,5-dimethoxy-4-methylphenethylamine (2C-D); 2,5-dimethoxy-4-ethylphenethylamine (2C-E); 2,5-dimethoxy-4-iodophenethylamine (2C-I); 2,5-dimethoxy-4-ethylthiophenethylamine (2C-T-2) and 2,5-dimethoxy-4-chloroamphetamine (DOC) are used recreationally and may have deleterious side effects.
This study compares behavioral effects and mechanisms of action of these substituted phenethylamines with those of hallucinogens and a stimulant.
The effects of these compounds on mouse locomotor activity and in rats trained to discriminate dimethyltryptamine, (−)DOM, (+)LSD, (±)MDMA and (S+)methamphetamine were assessed. Binding and functional activity of the phenethylamines at 5-HT1A, 5-HT2A, 5-HT2C receptors and monoamine transporters were assessed using cells heterologously expressing these proteins.
The phenethylamines depressed mouse locomotor activity, although 2C-D and 2C-E stimulated activity at low doses. The phenethylamines except 2C-T-2 fully substituted for at least one hallucinogenic training compound but none fully substituted for (+)-methamphetamine. At 5-HT1A receptors, only 2C-T-2 and 2C-I were partial-to-full very low potency agonists. In 5-HT2A arachidonic acid release assays, the phenethylamines were partial to full agonists except 2C-I which was an antagonist. All compounds were full agonists at 5-HT2A and 5-HT2C receptor inositol phosphate assays. Only 2C-I had moderate affinity for, and very low potency at, the serotonin transporter.
The discriminative stimulus effects of 2C-C, 2C-D, 2C-E, 2C-I and DOC were similar to those of several hallucinogens but not methamphetamine. Additionally, the substituted phenethylamines were full agonists at 5-HT2A and 5-HT2C receptors, but for 2C-T-2, this was not sufficient to produce hallucinogenlike discriminative stimulus effects. Additionally, the 5-HT2A inositol phosphate pathway may be important in 2C-I’s psychoactive properties.
Substituted phenethylamines; Drug discrimination; Serotonin receptor; Locomotor activity; Lysergic acid diethylamide (LSD); (-)-2,5-dimethoxy-4-methylamphetamine; Drug abuse
Intermittent hypoxia preconditioning (IHP) has been shown to protect neurons against ischemic stroke injury. Studying how proteins respond to IHP may identify targets that can help fight stroke. The objective of the present study was to investigate whether mitochondrial dihydrolipoamide dehydrogenase (DLDH) would respond to IHP and if so, whether such a response could be linked to neuroprotection in ischemic stroke injury. To do this, we subjected male rats to IHP for 20 days and measured the content and activity of DLDH as well as the three α-keto acid dehydrogenase complexes that contain DLDH. We also measured mitochondrial electron transport chain enzyme activities. Results show that DLDH content was indeed upregulated by IHP and this upregulation did not alter the activities of the three α-keto acid dehydrogenase complexes. Results also show that the activities of the five mitochondrial complexes (I-V) were not altered either by IHP. To investigate whether IHP-induced DLDH upregulation is linked to neuroprotection against ischemic stroke injury, we subjected both DLDH deficient mouse and DLDH transgenic mouse to stroke surgery followed by measurement of brain infarction volume. Results indicate that while mouse deficient in DLDH had exacerbated brain injury after stroke, mouse overexpressing human DLDH also showed increased brain injury after stroke. Therefore, the physiological significance of IHP-induced DLDH upregulation remains to be further investigated.
dihydrolipoamide dehydrogenase; intermittent hypoxic preconditioning; ischemic stroke; mitochondria; neuroprotection
Anecdotal reports have surfaced concerning misuse of the HIV antiretroviral medication efavirenz ((4S)-6-chloro-4-(2-cyclopropylethynyl)-4-(trifluoromethyl)-2,4-dihydro-1H-3,1-benzoxazin-2-one) by HIV patients and non-infected teens who crush the pills and smoke the powder for its psychoactive effects. Molecular profiling of the receptor pharmacology of efavirenz pinpointed interactions with multiple established sites of action for other known drugs of abuse including catecholamine and indolamine transporters, and GABAA and 5-HT2A receptors. In rodents, interaction with the 5-HT2A receptor, a primary site of action of lysergic acid diethylamine (LSD), appears to dominate efavirenz's behavioral profile. Both LSD and efavirenz reduce ambulation in a novel open-field environment. Efavirenz occasions drug-lever responding in rats discriminating LSD from saline, and this effect is abolished by selective blockade of the 5-HT2A receptor. Similar to LSD, efavirenz induces head-twitch responses in wild-type, but not in 5-HT2A-knockout, mice. Despite having GABAA-potentiating effects (like benzodiazepines and barbiturates), and interactions with dopamine transporter, serotonin transporter, and vesicular monoamine transporter 2 (like cocaine and methamphetamine), efavirenz fails to maintain responding in rats that self-administer cocaine, and it fails to produce a conditioned place preference. Although its molecular pharmacology is multifarious, efavirenz's prevailing behavioral effect in rodents is consistent with LSD-like activity mediated via the 5-HT2A receptor. This finding correlates, in part, with the subjective experiences in humans who abuse efavirenz and with specific dose-dependent adverse neuropsychiatric events, such as hallucinations and night terrors, reported by HIV patients taking it as a medication.
Addiction & Substance Abuse; adverse neuropsychiatric events; antiretroviral drug; Behavioral Science; hallucinogen; HIV; Neuropharmacology; Receptor Pharmacology; side effects; hallucinogen; adverse neuropsychiatric events; side effects; AIDS
Vascular dementia ranks as the second leading cause of dementia in the United States. However, its underlying pathophysiological mechanism is not fully understood and no effective treatment is available. The purpose of the current study was to evaluate long-term cognitive deficits induced by transient middle cerebral artery occlusion (tMCAO) in rats and to investigate the underlying mechanism. Sprague-Dawley rats were subjected to tMCAO or sham surgery. Behavior tests for locomotor activity and cognitive function were conducted at 7 or 30 days after stroke. Hippocampal long term potentiation (LTP) and involvement of GABAergic neurotransmission were evaluated at 30 days after sham surgery or stroke. Immunohistochemistry and Western blot analyses were conducted to determine the effect of tMCAO on cell signaling in the hippocampus. Transient MCAO induced a progressive deficiency in spatial performance. At 30 days after stroke, no neuron loss or synaptic marker change in the hippocampus were observed. LTP in both sides of the hippocampus was reduced at 30 days after stroke. This LTP impairment was prevented by blocking GABAA receptors. In addition, ERK activity was significantly reduced in both sides of the hippocampus. In summary, we identified a progressive decline in spatial learning and memory after ischemic stroke that correlates with suppression of hippocampal LTP, elevation of GABAergic neurotransmission, and inhibition of ERK activation. Our results indicate that the attenuation of GABAergic activity or enhancement of ERK/MAPK activation in the hippocampus might be potential therapeutic approaches to prevent or attenuate cognitive impairment after ischemic stroke.
stroke; long term potentiation; hippocampus; vascular dementia; cognition; GABA; ERK
A number of psychostimulant-like cathinone compounds are being sold as “legal” alternatives to methamphetamine or cocaine. The purpose of these experiments was to determine whether cathinone compounds stimulate motor activity and have discriminative stimulus effects similar to cocaine and/or methamphetamine. 3,4-Methylenedioxypyrovalerone (MDPV), methylone, mephedrone, naphyrone, flephedrone and butylone were tested for locomotor stimulant effects in mice and subsequently for substitution in rats trained to discriminate cocaine (10 mg/kg, i.p.) or methamphetamine (1 mg/kg, i.p.) from saline. All compounds fully substituted for the discriminative stimulus effects of cocaine and methamphetamine. Several commonly marketed cathinones produce discriminative stimulus effects comparable to those of cocaine and methamphetamine, which suggests that these compounds are likely to have similar abuse liability. MDPV and naphyrone produced locomotor stimulant effects that lasted much longer than cocaine or methamphetamine and therefore may be of particular concern, particularly since MDPV is one of the most commonly found substances associated with emergency room visits due to adverse effects from taking “bath salts”.
cathinones; drug discrimination; locomotor activity; abuse liability; mouse; rat
The molecular mechanisms underlying cognitive decline during healthy aging remain largely unknown. Utilizing aged wild-type C57BL/6 mice as a model for normal aging, we tested the hypothesis that cognitive performance, memory, and learning as assessed in established behavioral testing paradigms are correlated with the differential expression of isoforms of the Homer family of synaptic scaffolding proteins. Here we describe a loss of cognitive and motor function that occurs when Homer-1a/Vesl-1S protein levels drop during aging. Our data describe a novel mechanism of age-related synaptic changes contributing to loss of biological function, spatial learning, and memory formation as well as motor coordination, with the dominant negative uncoupler of synaptic protein clustering, Homer-1a/Vesl-1S, as a potential target for the prophylaxis and treatment of age-related cognitive decline.
Electronic supplementary material
The online version of this article (doi:10.1007/s11357-012-9479-6) contains supplementary material, which is available to authorized users.
Behavior; Cognition; Cognitive aging; Learning; Memory; Synapse
Coenzyme Q10 (CoQ) is widely available as a dietary supplement and remains under consideration as a treatment for age-associated neurodegenerative conditions. However, no studies have determined if supplementation, initiated relatively late in life, could have beneficial effects on mild functional impairments associated with normal brain aging. Accordingly, the current study assessed the effect of CoQ intake in older mice for which cognitive and psychomotor impairments were already evident. Separate groups of young (3.5 months) and relatively old mice (17.5 months) were fed a control diet or a diet supplemented with low (0.72 mg/g) or high (2.81 mg/g) concentrations of CoQ for 15 weeks. After 6 weeks, the mice were given tests for spatial learning (Morris water maze), spontaneous locomotor activity, motor coordination, and startle reflex. Age-related impairments in cognitive and psychomotor functions were evident in the 17.5-month-old mice fed the control diet, and the low-CoQ diet failed to affect any aspect of the impaired performance. However, in the Morris water maze test, old mice on the high-CoQ diet swam to the safe platform with greater efficiency than the mice on the control diet. The old mice supplemented with the high-CoQ diet did not show improvement when spatial performance was measured using probe trials and failed to show improvement in other tests of behavioral performance. Protein oxidative damage was decreased in the mitochondria from the heart, liver, and skeletal muscle of the high-CoQ-supplemented mice and, to some extent, in the brain mitochondria. Contrasting with the deleterious effect of long-term CoQ supplementation initiated during young adulthood previously published, this study suggests that CoQ improves spatial learning and attenuates oxidative damage when administered in relatively high doses and delayed until early senescence, after age-related declines have occurred. Thus, in individuals with age-associated symptoms of cognitive decline, high-CoQ intake may be beneficial.
Aging; Coenzyme Q10; Ubiquinone; Ubidecarenone; C57BL/6J; Oxidative damage; Mitochondria
Serotonergic hallucinogens such as (+)-lysergic acid diethylamide (LSD) and dimethyltryptamine (DMT) produce distinctive visual effects, whereas the synthetic hallucinogen N,N-diisopropyltryptamine (DiPT) is known for its production of auditory distortions. Objective: This study compares the discriminative stimulus effects of DiPT to those of visual hallucinogens.
Adult male rats were trained to discriminate DiPT (5 mg/kg, 15 min) from saline under a FR10 schedule. A dose-effect and time course of DiPT’s discriminative stimulus effects were established. DMT, (−)-2,5-dimethoxy-4-methylamphetamine (DOM), LSD, (±)-methylenedioxymethamphetamine (MDMA) and (+)-methamphetamine were tested for cross-substitution in DiPT-trained animals.
Rats learned to discriminate DiPT from saline in an average of 60 training sessions (30 drug and 30 saline). DiPT (0.5 – 5 mg/kg) produced dose-dependent increases in drug-appropriate responding (DAR) to 99% (ED50 = 2.47 mg/kg). Onset of the discriminative stimulus effects was within 5 minutes and the effects dissipated within 4 hours. Full substitution for the discriminative stimulus effects of DiPT occurred with LSD, DOM and MDMA. DMT only partially substituted for DiPT (65% DAR), whereas (+)-methamphetamine failed to substitute for DiPT (29% DAR).
The discriminative stimulus effects of DiPT were similar those of a number of synthetic hallucinogens, only partially similar to those of DMT, but not similar to (+)-methamphetamine. The putative DiPT-induced auditory distortions do not lead to discriminative stimulus effects distinguishable from other hallucinogens.
N,N-Diisopropyltryptamine; hallucinogens; drug discrimination; rat
Ethanol and cocaine are frequently abused in combination, but little is known about how the subjective effects of the two drugs interact. The ability of ethanol and other GABAA-active compounds to alter the discriminative stimulus effects of cocaine was tested. Male Sprague-Dawley rats were trained to discriminate cocaine (10 mg/kg, i.p.) from saline using either single-dose or cumulative dosing methods. In single-dose testing, ethanol (0.1 to 0.5 g/kg) dose-dependently decreased cocaine-appropriate responding following the training dose of cocaine. Ethanol (0.5 g/kg) produced a rightward shift in the cocaine cumulative dose-effect curve. Ethanol (0.1 to 1.0 g/kg) failed to substitute for the discriminative stimulus effects of cocaine and the higher doses (1 to 2 g/kg) completely suppressed responding. Indirect GABAA agonists diazepam (benzodiazepine site) and pentobarbital (barbiturate site) did not block the discriminative stimulus effects of cumulative doses of cocaine. The GABAA antagonist pentylenetetrazol (10 to 40 mg/kg) did not substitute for cocaine. These findings suggest that ethanol can modulate the discriminative stimulus effects of cocaine, and that these effects may not be mediated by the actions of ethanol at the GABAA receptor.
Cocaine; ethanol; drug discrimination; GABAA receptor; rat
This study tested the time course of the discriminative stimulus effects of inhibitors of monoamine oxidase (MAO) alone or in combination with cocaine. Male Sprague-Dawley rats were trained to discriminate cocaine (10 mg/kg, i.p.) from saline using a two-lever choice methodology. The non-selective MAO inhibitors tranylcypromine (0.01 to 5 mg/kg) and phenelzine (1 to 25 mg/kg), the MAO-A selective compound clorgyline (1 to 25 mg/kg), and the MAO-B selective compounds pargyline (0.005 to 50 mg/kg) and selegiline (1 to 25 mg/kg) were tested for substitution 15 min or 24 hr following administration, and in combination with 10 mg/kg of cocaine 24 and 48 hr after administration. At 15 min, selegiline fully substituted for the discriminative stimulus effects of cocaine, whereas all other compounds partially substituted. At 24 hr, substitution of cocaine was diminished for all compounds except phenelzine, which produced a greater amount of substitution at 24 hr than at 15 min. When cocaine was administered 24 hr following clorgyline, selegiline, pargyline, and phenelzine, cocaine-appropriate responding was attenuated at intermediate doses of these drugs, whereas the highest doses did not alter cocaine-lever responding. All compounds except selegiline substantially decreased response rate and produced various adverse effects. At 48 hr, the effects of all compounds except phenelzine were markedly reduced. Selectivity for MAO-A or B did not predict the ability to substitute for or attenuate the subjective effects of cocaine. These findings suggest that MAO inhibitors can modulate the discriminative stimulus effects of cocaine for at least 24 hr, and may be useful for treatment of cocaine abuse.
Cocaine; drug discrimination; dopamine receptors; monoamine oxidase inhibitors; rat
Long-term caloric restriction (CR) has been repeatedly shown to increase life span and delay the onset of age-associated pathologies in laboratory mice and rats. The purpose of the current study was to determine whether the CR-associated increase in life span occurs in all strains of mice or only in some genotypes and whether the effects of CR and ad libitum (AL) feeding on mortality accrue gradually or are rapidly inducible and reversible. In one experiment, groups of male C57BL/6, DBA/2, and B6D2F1 mice were fed AL or CR (60% of AL) diets beginning at 4 months of age until death. In the companion study, separate groups of mice were maintained chronically on AL or CR regimens until 7, 17, or 22–24 months of age, after which, half of each AL and CR group was switched to the opposite regimen for 11 wk. This procedure yielded four experimental groups for each genotype, namely AL→AL, AL→CR, CR→CR, and CR→AL, designated according to long-term and short-term caloric regimen, respectively. Long-term CR resulted in increased median and maximum life span in C57BL/6 and B6D2F1 mice but failed to affect either parameter in the DBA/2 mice. The shift from AL→CR increased mortality in 17- and 24-month-old mice, whereas the shift from CR→AL did not significantly affect mortality of any age group. Such increased risk of mortality following implementation of CR at older ages was evident in all three strains but was most dramatic in DBA/2 mice. Results of this study indicate that CR does not have beneficial effects in all strains of mice, and it increases rather than decreases mortality if initiated in advanced age.
caloric restriction; aging; C57BL/6; DBA/2; B6D2F1
Under oxidative stress conditions, mitochondria are the major site for cellular production of reactive oxygen species (ROS) such as superoxide anion and H2O2 that can attack numerous mitochondrial proteins including dihydrolipoamide dehydrogenase (DLDH). While DLDH is known to be vulnerable to oxidative inactivation, the mechanisms have not been clearly elucidated. The present study was therefore designed to investigate the mechanisms of DLDH oxidative inactivation by mitochondrial reactive oxygen species (ROS). Mitochondria, isolated from rat brain, were incubated with mitochondrial respiratory substrates such as pyruvate/malate or succinate in the presence of electron transport chain inhibitors such as rotenone or antimycin A. This is followed by enzyme activity assay and gel-based proteomic analysis. The present study also examined whether ROS-induced DLDH oxidative inactivation could be reversed by reducing reagents such as DTT, cysteine, and glutathione. Results show that DLDH could only be inactivated by complex III- but not complex I-derived ROS; and the accompanying loss of activity due to the inactivation could be restored by cysteine and glutathione, indicating that DLDH oxidative inactivation by complex III-derived ROS was a reversible process. Further studies using catalase indicate that it was H2O2 instead of superoxide anion that was responsible for DLDH inactivation. Moreover, using sulfenic acid-specific labeling techniques in conjunction with two-dimensional Western blot analysis, we show that protein sulfenic acid formation (also known as sulfenation) was associated with the loss of DLDH enzymatic activity observed under our experimental conditions. Additionally, such oxidative modification was shown to be associated with preventing DLDH from further inactivation by the thiol-reactive reagent N-ethylmaleimide. Taken together, the present study provides insights into the mechanisms of DLDH oxidative inactivation by mitochondrial H2O2.
brain; dihydrolipoamide dehydrogenase; H2O2; mitochondria; reactive oxygen species; reversible inactivation; sulfenic acid; sulfenation
The objectives of this study were: (i) to identify regions of the aged mouse brain in which advanced glycation end-products (AGEs) were increased, and (ii) assess the functional significance of AGEs by assessing the extent to which they could predict age-related brain dysfunction. Densitometric analyses of immunoblots for N epsilon-(carboxymethyl)lysine (CML), a predominant AGE, and receptor for AGE (RAGE), were performed in different brain regions of mice aged 8 or 25 months. The 25-month-old mice were tested for ability to perform on tests of cognitive and psychomotor function prior to assessment of CML or RAGE, to determine if immunostaining results could predict functional impairment among the older mice. The amounts of CML increased with age in cortex, hippocampus, striatum and midbrain, but were unchanged in the brainstem and cerebellum. Increases in RAGE were evident in all brain regions but the hippocampus, and were not linked to increased amounts of CML. Different statistical approaches each failed to reveal any strong association between the degree of age-related functional impairment among individual mice and amounts of CML or RAGE in any particular region of the brain. The findings from this study suggest that accrual of CML and expression of RAGE in different brain regions are time-related phenomena that do not account for individual differences in brain aging or cognitive decline.
Advanced glycation end products; N epsilon-(carboxymethyl) lysine; Receptor for advanced glycation end products; Central nervous system; Aging; Motor function; Behavior
Carisoprodol is a muscle relaxant that acts at the GABAA receptor. Concerns about the abuse liability of carisoprodol are increasing, but evidence that carisoprodol produces tolerance and a significant withdrawal syndrome has yet to be established. The purpose of the current study was to determine if repeated administration of carisoprodol produces tolerance and withdrawal signs in a mouse model.
Carisoprodol (0, 100, 200, 300, or 500 mg/kg bid, i.p.) was administered to Swiss-Webster mice for 4 days and loss-of-righting reflex was measured 20 to 30 minutes following each administration. On the fourth day, bemegride (20 mg/kg), flumazenil (20 mg/kg), or vehicle was administered following carisoprodol and withdrawal signs were measured. Separate groups of mice receiving the same treatment regimen and dose range were tested for spontaneous withdrawal at 6, 12 and 24 hr after the last dose of carisoprodol.
The righting reflex was dose-dependently impaired following the first administration of carisoprodol. A 75 to 100% decrease in the magnitude of the impairment occurred over the four days of exposure, indicating the development of tolerance to the carisoprodol-elicited loss-of-righting reflex. Withdrawal signs were not observed within 24 hours following spontaneous withdrawal; however, bemegride and flumazenil each precipitated withdrawal within 15 to 30 min of administration.
Carisoprodol treatment resulted in tolerance and antagonist-precipitated withdrawal, suggesting it may have an addiction potential similar to that of other long-acting benzodiazepine or barbiturate compounds.
tolerance; precipitated withdrawal; carisoprodol; GABAA receptor; barbiturate site; benzodiazepine site; bemegride; flumazenil; mouse
Diagnosis and treatment of common conditions in morbidly obese patients still pose a challenge to physicians and surgeons. Sometimes too much reliance is put on investigations that can lead to a misdiagnosis. This case demonstrates an obese woman admitted under the medical team with a presumed diagnosis of pneumonia, who was later found to have an acute abdomen and raised amylase, which led to an assumed diagnosis of pancreatitis. She died within 24 h of admission and post mortem confirmed the cause of death as systemic sepsis due to perforated appendicitis, with no evidence of pancreatitis. Significantly elevated serum amylase level may occur in non-pancreatitic acute abdomen.
Morbid obesity; Perforated appendicitis; Pneumonia; Serum amylase
The hypothesis that life span extension by caloric restriction (CR) is contingent upon the attenuation of macromolecular oxidative damage was tested in two different strains of mice: the C57BL/6, whose life span is extended by CR, and the DBA/2, in which CR has relatively minor or no impact on longevity. Mice were fed ad libitum (AL) or restricted to 40% lesser food, starting at 4 months of age. Protein damage was measured as protein-linked adducts of 4-hydroxy-2-nonenal (HNE) and malondialdehyde (MDA) in skeletal muscle mitochondria at 6- and 23-months of age. Protein-HNE and -MDA content increased with age in C57BL/6 mice and CR significantly attenuated these augmentations. Metalloprotease 1, NADP-dependent mitochondrial malic enzyme (isoform 2) and citrate synthase were identified by mass spectroscopy to contain HNE/MDA adducts. DBA/2 mice exhibited little effect of age or CR on protein HNE/MDA content in skeletal muscle mitochondria. In contrast, protein-HNE levels in liver mitochondria showed a significant increase with age in AL-fed mice of both strains, and CR caused significant attenuation of this damage. Overall, results indicated that the age-related increase in protein oxidative damage and its abatement by CR are genotype- and tissue- specific, and not a universal phenomenon.
HNE-protein conjugates; oxidative stress; protein oxidative damage; mitochondrial proteins; food restriction