Inhibitory Control of the Abdominal Stretch Receptors of the Crayfish

By stretch activation of the slowly adapting abdominal stretch receptor of the crayfish, we have found reflex activation of two efferent spikes of different amplitudes in the dorsal nerves of the same and neighbouring segments. The large as well as the small efferent spike inhibit the discharge of the receptor. It is suggested that these two units represent the thick and thin accessory fiber described by Alexandrowicz, as making synaptic contacts with the receptor cell.