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A COMPARATIVE STUDY OF THE ACTION OF γ‐AMINOBUTYRIC ACID AND PIPERAZINE ON THE LOBSTER MUSCLE FIBRE AND THE FROG SPINAL CORD
Author(s) -
CONSTANTI A.,
NISTRI A.
Publication year - 1976
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.1476-5381.1976.tb07673.x
Subject(s) - picrotoxin , tetrodotoxin , depolarization , spinal cord , nipecotic acid , biophysics , chemistry , piperazine , gamma aminobutyric acid , anatomy , biology , gabaa receptor , pharmacology , biochemistry , receptor , neuroscience , neurotransmitter
1 The effects of γ‐aminobutyric acid (GABA) and piperazine were compared on two in vitro preparations, the lobster muscle fibre and the frog spinal cord. 2 Both GABA and piperazine increased the membrane conductance of single lobster muscle fibres without changing the membrane potential; sigmoidal log dose‐conductance curves for these agents were obtained and a similar model expressed the receptor interaction of both substances. 3 The actions of GABA and piperazine on lobster muscle were antagonized by picrotoxin and were Cl − ‐dependent. 4 In the frog spinal cord GABA depolarized the dorsal roots presumably by mimicking the activity of the transmitter depolarizing the primary afferents; sigmoidal log dose‐response curves for GABA were obtained. 5 On the dorsal roots piperazine produced either depolarizations or biphasic responses; these were mainly indirect effects as was shown by experiments in the presence of tetrodotoxin (TTX). 6 The effects of GABA on the dorsal root (in TTX‐treated cords) were antagonized by picrotoxin whereas those of piperazine were more resistant to this alkaloid. The GABA‐induced responses appeared to be largely Na + ‐dependent while both Na + and Cl − seemed to mediate the effects of piperazine. 7 It is proposed that piperazine has GABA‐agonist activity on lobster muscle but little GABA‐like activity on the frog spinal cord.