Functional and pharmacological differences between two types of GABA receptor on embryonic chick sensory neurons.
Embryonic chick sensory neurons grown in dissociated cell culture exhibit two functional responses to GABA: an increase in resting membrane permeability to chloride (Cl) ions (resulting in membrane depolarization) and a decrease in voltage-dependent calcium (Ca) channel current (resulting in a decreased action potential duration). These two functional effects differ in a number of ways. (1) The increase in resting membrane permeability desensitizes in the maintained presence of GABA, while the decrease in action potential duration does not. (2) Muscimol is a selective agonist for the increase in resting conductance, while baclofen is a selective agonist for the decrease in action potential duration. (3) Bicuculline inhibits the GABA- or muscimol-induced increase in Cl permeability, but it does not block the GABA- or baclofen-induced decrease in action potential duration. These functional and pharmacological differences between the two effects of GABA suggest that two separate receptors are involved.
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002642:Chick Embryo; D002712:Chlorides / Q000378:metabolism; D046508:Culture Techniques; D005727:Ganglia, Spinal / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D011963:Receptors, GABA-A; D011984:Sensory Receptor Cells / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D002712:Chlorides; D007473:Ion Channels; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D002118:Calcium; D001640:Bicuculline