Acetylcholine and GABA mediate opposing actions on neuronal chloride channels in crayfish.
A central principle of neural integration is that excitatory and inhibitory neurotransmitters effect the opening of distinct classes of membrane ionic channels and that integration consists of the summation of the opposing ionic currents on the postsynaptic membrane. In tangential cells of crayfish optic lobes, a hyperpolarizing, biphasic synaptic potential is produced by the concurrent action of acetylcholine and gamma aminobutyric acid (GABA). Acetylcholine hyperpolarizes the cell and increases chlorine conductance. GABA depolarizes the cell by closing some of the same chloride channels. Therefore, in this case integration is achieved by the antagonistic actions of two transmitters on the same ionic channel.
Pfeiffer-Linn
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Department of Biology, Rice University, Houston TX 77251.
Glantz
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D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D003400:Astacoidea; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009899:Optic Lobe, Nonmammalian; D010852:Picrotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D000109:Acetylcholine; D002712:Chlorides; D007473:Ion Channels; D010852:Picrotoxin; D005680:gamma-Aminobutyric Acid