Serotonin and proctolin modulate the response of a stretch receptor in crayfish

The modulatory effects of proctolin and a biogenic amine (5-hydroxytryptamine; 5-HT) have been investigated on a leg mechanoreceptor in the crayfish. Single afferent sensory units were recorded extra- and intracellularly during imposed sinusoidal movement to the receptor strand; all responses were facilitated by a bath application of proctolin and 5-HT at various concentrations (10(-9)-10(-6) M).