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Inhibition of calcium spikes and transmitter release by γ‐aminobutyric acid in the guinea‐pig myenteric plexus
Author(s) -
Cherubini E.,
North R. A.
Publication year - 1984
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1984.tb16446.x
Subject(s) - bicuculline , acetylcholine , excitatory postsynaptic potential , chemistry , tetrodotoxin , cholinergic , neurotransmission , myenteric plexus , biophysics , membrane potential , inhibitory postsynaptic potential , calcium , reversal potential , endocrinology , neuroscience , medicine , electrophysiology , biology , gabaa receptor , biochemistry , patch clamp , receptor , immunohistochemistry , organic chemistry
1 The effect of γ‐aminobutyric acid (GABA) (1 μ M ‐1 m M ) on synaptic transmission in isolated myenteric ganglia of guinea‐pig ileum was investigated with intracellular recording techniques. 2 GABA (up to 1 m M ) had no effect on the resting membrane potential and membrane conductance of S neurones. 3 GABA reduced the amplitude of the fast excitatory postsynaptic potential (e.p.s.p.) without changing the amplitude of the nicotinic response to ionophoretic application of acetylcholine (ACh). This effect was mimicked by baclofen (10–100 μ M ) and was not blocked by bicuculline (10 μ M ). The preparation did not become desensitized during prolonged GABA applications. 4 Cholinergic and non‐cholinergic slow e.p.s.ps evoked by single or repetitive presynaptic nerve stimulation were reduced in amplitude by GABA. GABA did not depress muscarinic responses to ionophoretic application of ACh. 5 GABA reduced the duration of the action potential in AH neurones in concentrations that did not affect the membrane potential or conductance. The effect was very marked when electrodes were filled with CsCl, and tetrodotoxin was in the supervising solution. This effect was also mimicked by baclofen, was insensitive to bicuculline and was not reduced with repeated application or GABA. 6 It is concluded that GABA inhibits release of ACh and the transmitter mediating the slow e.p.s.p. This effect may result from inhibition of an inward calcium current.