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Bicuculline and picrotoxin as antagonists of γ-aminobutyrate and neuromuscular inhibition in the lobster

1974; Elsevier BV; Volume: 72; Issue: 1 Linguagem: Inglês

10.1016/0006-8993(74)90651-9

1872-6240

Richard P. Shank, S.F. Pong, A. R. Freeman, L.T. Graham,

Conducting polymers and applications

Bicuculline at 2 × 10−4M has a small but consisten antagonisctic effect on neurally-evoked neuromuscular inhibition in the lobster. This drug similarly antagonized the action of exogenously applied GABA. Picrotoxin at 2 × 10−6M had a greater antagonistic effect on both neurally evoked inhibition and the activity of applied GABA. Judging from the effects of bicuculline and picrotoxin on dose-response curves for GABA, the antagonistic properties of the two alkaloids appeared to be different in nature. The action of bicuculline appeared to be non-competitive whereas that of picrotoxin seemed to be more consistent with competitive antagonism. Bicuculline increased the amplitude of excitatory postsynaptic potentials recorded from the muscle fibers. This latter effect may be a consequence of a drug-induced increase in the resistance of the non-synaptic membrane. Hence, in addition to its action on GABA receptors, bicuculline appears to have non-synaptic effects which broaden the interpretation of its pharmacological activity.