Differential effects of GABA on three muscles innervated by a common inhibitory axon ofOcypode

Summary The effect of GABA (-aminobutyric acid) on three muscles innervated by the common inhibitory axon in the walking leg of the crabOcypode cursor, was studied. The muscles differ in the percentage of fibres responding to GABA by membrane resistance decrease, and in the magnitude of the response (Table 1). In addition to the postsynaptic effect (on muscle fibre membrane) of GABA, a presynaptic effect (on excitatory terminals) was observed in one muscle, resulting in more effective inhibition of excitatory potentials. The presynaptic effect sustained as long as GABA was present, while the postsynaptic effect underwent desensitization (Fig. 2). The data demonstrate differential inhibition of distinct functional units innervated by a common axon. The channeling of inhibitory information results from spatial organization of innervation, differing in location (pre-or postsynaptic) and density.This investigation was supported by grant AZ11 1955 for Stiftung Volkswagenwerk.