Adaptation of the generator potential in the crayfish stretch receptors under constant length and constant tension.

1. Generator potentials were investigated in stretch receptors of crayfish after abolishing spike potentials with tetrodotoxin.2. The time courses of the decline of generator potential (generator adaptation) were almost the same in the slowly and rapidly adapting receptors.3. The time courses of the tension changes after suddenly stretching the receptor muscles did not differ much between the two receptor types.4. The amplitudes of generator potential per unit stress or per unit strain in the receptor muscle were roughly the same in the two receptor types.5. By comparing generator adaptation under length-clamp and tension-clamp in the slowly adapting receptors, it was suggested that roughly 70% of the generator adaptation could be explained by a simple visco-elastic property of the receptor muscle, when observed for 1 sec after the beginning of the stretch.6. It was concluded that the marked differences in the receptor adaptation between the two receptor types were attributable to the differences in the properties of spike generating membrane rather than to the properties of the generator potentials.7. In each type of receptor, both the generator adaptation and the adaptation of spike generating mechanisms contributed to determining the whole rates of receptor adaptation. In the slowly adapting receptor, however, the generator adaptation seemed more important, while in the rapidly adapting receptor the spike generating mechanisms seemed more important.