Gamma-Aminobutyric Acid and Other Blocking Substances extracted from Crab Muscle

Abstract

As part of an attempt to identify the transmitter agent released by inhibitory nerves in crustacean muscle we have extracted and purified heat-stable ‘inhibitory’ substances of a crab muscle and its associated nerve supply. The fibres of the extensor muscle (opener) of the dactyl of the walking leg of Cancer borealis are densely innervated by two inhibitory nerve fibres, and by extracting the whole muscle, although adding non-neural elements, we were assured of obtaining the materials stored within the nerve endings. The extracts were assayed on the extensor muscle of the dactyl in the crayfish, Orconectes virilis. Only those extracts which imitated the effect produced by neural inhibitory activity (reduction of the excitatory junctional potentials without shifting the resting potential by more than 5 mV.) were considered ‘inhibitory’ and were further purified.