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Differential effects of iontophoretic in vivo application of the GABA A-antagonists bicuculline and gabazine in sensory cortex

Lookup NU author(s): Dr John Crook

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Abstract

We have compared the effects of microiontophoretic application of the GABAA-receptor antagonists bicuculline (BIC) and gabazine (SR95531) on responses to pure tones and to sinusoidally amplitude-modulated (AM) tones in cells recorded extracellularly from primary auditory cortex (AI) of Mongolian gerbils. Besides similar effects in increasing spontaneous and stimulus-evoked activity and their duration, both drugs elicited differential effects on spectral tuning and synchronized responses to AM tones. In contrast to gabazine, iontophoresis of the less potent GABAA-antagonist BIC often resulted in substantial broadening of frequency tuning for pure tones and an elimination of synchronized responses to AM tones, particularly with high ejecting currents. BIC-induced effects which could not be replicated by application of gabazine were presumably due to the well-documented, non-GABAergic side-effects of BIC on calcium-dependent potassium channels. Our results thus provide strong evidence that GABAA-mediated inhibition in AI does not sharpen frequency tuning for pure tones, but rather contributes to the processing of fast temporal modulations of sound envelopes. They also demonstrate that BIC can have effects on neuronal response selectivity which are not due to blockade of GABAergic inhibition. The results have profound implications for microiontophoretic studies of the role of intracortical inhibition in sensory cortex. © 2006 Elsevier B.V. All rights reserved.


Publication metadata

Author(s): Kurt S, Crook JM, Ohl FW, Scheich H, Schulze H

Publication type: Article

Publication status: Published

Journal: Hearing Research

Year: 2006

Volume: 212

Issue: 1-2

Pages: 224-235

ISSN (print): 0378-5955

ISSN (electronic): 1878-5891

Publisher: Elsevier BV

URL: http://dx.doi.org/10.1016/j.heares.2005.12.002

DOI: 10.1016/j.heares.2005.12.002

PubMed id: 16442250


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