The Cyclic Production of 5-Hydroxytryptamine in the Opilionid

Abstract

Techniques were developed for the measurement of two cyclic responses in the opilionid, Leiobunum longipes. These responses were an overt locomotor behavior and an internal secretory activity, both measured over a 24-hour period. An activity platform was designed to measure and to record continuously the movements of the opilionid. The procedure of fluorometric analysis, used to quantitate indoles, was adapted for use with the opilionid and the presence of the neurosecretory compound, 5-hydroxytryptamine, was established. A method was developed for maintaining tissues in culture over extended periods. Adult males and females of Leiobunum longipes showed a unimodal pattern of locomotor activity. The pattern of secretion of 5-HT was also shown to be unimodal in character. There was an interesting parallel between the patterns of activity and secretion of 5-HT, with greatest peak at 2:00 AM, which suggested a relationship between the two. The secretion, of 5-HT from tissues in vitro showed a bimodal cyclic output with a primary peak at 2:00 AM. A secondary peak occurred at midmorning, when the secretion in intact animals was at a low point.