The GABA dose/conductance relationship on lobster muscle.
A quantitative study was made of the action of GABA, some structurally-related agonists and antagonists on the dactyl opener muscle fibres of the lobster. It was concluded that the GABA dose/conductance relationship was better described by a two independent binding-site receptor model (with KII = 30 microM) than by a single-site or a two-site high co-operativity model. The dose/conductance curves for gamma-amino-beta-hydroxybutyric acid (GABOB), delta-aminovaleric acid (DAV) and piperazine indicated 'full' agonist behaviour, whereas those for guanidoacetic acid (GuAc) indicated a partial agonist action. beta-guanidinopropionic acid (beta-GP) and gamma-guanidinobutyric acid (gamma-GB) behaved as weak competitive GABA antagonists. Bicuculline was found to antagonize GABA non-competitively on the lobster as in the crayfish, whereas picrotoxin appeared to act in a 'mixed' antagonistic fashion.
D000596:Amino Acids / Q000494:pharmacology; D021542:Amino Acids, Neutral; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D018756:GABA Antagonists; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D066298:In Vitro Techniques; D009132:Muscles / Q000187:drug effects*; D008121:Nephropidae; D010852:Picrotoxin / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D014631:Valerates / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives / Q000494:pharmacology*
D000596:Amino Acids; D021542:Amino Acids, Neutral; D001640:Bicuculline; D018756:GABA Antagonists; D005998:Glycine; D006146:Guanidines; D010852:Picrotoxin; D010879:Piperazines; D011422:Propionates; D014631:Valerates; D005680:gamma-Aminobutyric Acid; C001317:gamma-guanidinobutyric acid; C004480:4-amino-3-hydroxybutyric acid; C013809:5-aminovaleric acid; C004946:glycocyamine; C005775:guanidinopropionic acid