GAMMA-AMINOBUTYRIC ACID AND OTHER BLOCKING COMPOUNDS IN CRUSTACEA: II. PERIPHERAL NERVOUS SYSTEM

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Abstract
Two efferent axons of similar diameter, one inhibitory the other excitatory, run side by side in the leg of the lobster (Homarus americanus). Long unbranched stretches of these neurons were removed and separated; the isolated axons were analyzed for their content of gamma-aminobutyric acid (GABA) and 9 other synaptic blocking compounds that had been previously found in the crustacean nervous system. The GABA contents were compared enzymically; the contents of the other blocking substances were compared chromatographically or by physiological assay. The GABA content along the course of the inhibitory axon was about 0.5% of its wet weight, while no GABA was detected in the accompanying excitatory fiber. GABA may therefore De confined to inhibitory nerves. The other blocking compounds with the possible exception of [beta]-alanine, were found in both neuron types. The distribution of [beta]-alanine (a much weaker blocking substance than GABA) cannot be stated with confidence. The findings indicate that GABA has a function specifically related to inhiDitory neurons.[long dash]Authors.