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PLoS ONE (1)
The Journal of Neuroscience (1)
Burger, R Michael (1)
Burger, R. Michael (1)
Eble, Diane M. (1)
Fukui, Iwao (1)
Gerhart, Sarah V. (1)
Iovine, M. Kathryn (1)
Jefferis, Rebecca (1)
Mueller, Ferenc (1)
Ohmori, Harunori (1)
Oline, Stefan N. (1)
Rubel, Edwin W (1)
Sadler, Kirsten C. (1)
Vacaru, Ana (1)
Year of Publication
GABAergic inhibition sharpens the frequency tuning and enhances phase locking in chicken nucleus magnocellularis neurons
Rubel, Edwin W
The Journal of Neuroscience
GABAergic modulation of activity in avian cochlear nucleus neurons has been studied extensively in vitro. However, how this modulation actually influences processing in vivo is not known. We investigated responses of chicken nucleus magnocellularis (NM) neurons to sound while pharmacologically manipulating the inhibitory input from the superior olivary nucleus (SON). SON receives excitatory inputs from nucleus angularis (NA) and nucleus laminaris (NL), and provides GABAergic inputs to NM, NA, NL, and putatively to the contralateral SON. Results from single unit extracellular recordings from 2–4 wks posthatch chickens show that firing rates of auditory nerve fibers (ANFs) increased monotonically with sound intensity, while that of NM neurons saturated or even decreased at moderate or loud sound levels. Blocking GABAergic input with local application of TTX into the SON induced an increase in firing rate of ipsilateral NM while that of the contralateral NM decreased at high sound levels. Moreover, local application of bicuculline to NM also increased the firing rate of NM neurons at high sound levels, reduced phase-locking, and broadened the frequency tuning properties of NM neurons. Following application of DNQX, clear evidence of inhibition was observed. Furthermore, the inhibition was tuned to a broader frequency range than the excitatory response areas. We conclude that GABAergic inhibition from SON has at least three physiological influences on the activity of NM neurons: it regulates the firing activity of NM units in a sound-level dependent manner; it improves phase selectivity; and it sharpens frequency tuning of NM neuronal responses.
Superior olivary nucleus; Cochlear nucleus; Bicuculline; GABA; Auditory; In vivo
The Cx43-like Connexin Protein Cx40.8 Is Differentially Localized during Fin Ontogeny and Fin Regeneration
Gerhart, Sarah V.
Eble, Diane M.
Oline, Stefan N.
Sadler, Kirsten C.
Iovine, M. Kathryn
Connexins (Cx) are the subunits of gap junctions, membraneous protein channels that permit the exchange of small molecules between adjacent cells. Cx43 is required for cell proliferation in the zebrafish caudal fin. Previously, we found that a Cx43-like connexin, cx40.8, is co-expressed with cx43 in the population of proliferating cells during fin regeneration. Here we demonstrate that Cx40.8 exhibits novel differential subcellular localization in vivo, depending on the growth status of the fin. During fin ontogeny, Cx40.8 is found at the plasma membrane, but Cx40.8 is retained in the Golgi apparatus during regeneration. We next identified a 30 amino acid domain of Cx40.8 responsible for its dynamic localization. One possible explanation for the differential localization is that Cx40.8 contributes to the regulation of Cx43 in vivo, perhaps modifying channel activity during ontogenetic growth. However, we find that the voltage-gating properties of Cx40.8 are similar to Cx43. Together our findings reveal that Cx40.8 exhibits differential subcellular localization in vivo, dependent on a discrete domain in its carboxy terminus. We suggest that the dynamic localization of Cx40.8 differentially influences Cx43-dependent cell proliferation during ontogeny and regeneration.
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