Mechanisms of hyperpolarizing effect of GABA on resting potential of the Lumbricus terrestris muscular wall somatic cells

GABA, baclofen, isoguvacine increase, and cis-4-aminocrotonic acid does not modify resting membrane potential of muscle cells. Bicuculline, phaclofen, N-ethylmaleimide, chlorpromazine, verapamil, and removal of Ca2+ from bathing solution abolished the effect of baclofen, while U73122 and D609 were ineffective in this respect. The authors conclude that the Lumbricus terrestris muscle cells contain GABAergic structures similar to a- and b-receptors. Activation of GABA receptors induced Cl- inward current and Ca2+ entry with subsequent activation of calmodulin-like proteins, which causes membrane hyperpolarization by increasing the effect of "pumping potential" on resting membrane potential.