Unusual features of GABA responses in layers IV-V neurons of neocortex.
Perikaryal application of GABA produced a hyperpolarization and increased the input conductance in neurons of layers IV-V of neocortex (guinea pig). This response faded during brief applications and had a long duration when the application period was increased from 4s to greater than 10 s. The sensitivity of the first response to blockade by the selective antagonist, bicuculline, indicated a mediation by gamma-aminobutyric acid-A (GABAA) receptors. The longer duration response was mimicked to some extent by the GABAB agonist, baclofen. Dendritic application of GABA induced a depolarization and a conductance increase - a response which was not particularly sensitive to antagonism by bicuculline. The depolarizing response also did not have a clearly defined reversal potential and may be a consequence of complex changes in membrane conductance, possibly for Cl and Ca or Na. Fading in both types of responses may result from a concomitant postsynaptic activation of a Cl conductance with Na-dependent GABA uptake.
el-Beheiry
H
H
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Puil
E
E
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D003712:Dendrites / Q000187:drug effects; D004553:Electric Conductivity; D004594:Electrophysiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline