BIOCHEMICAL AND PHYSIOLOGICAL-EFFECTS OF OCTOPAMINE AND SELECTED OCTOPAMINE AGONISTS ON THE OVIDUCTS OF LOCUSTA-MIGRATORIA

The effects of octopamine and some selected octopamine agonists on neurally-evoked contractions and cyclic AMP levels of the lateral oviducts of the locust, Locusta migratoria, have been examined. Octopamine caused reversible, dose-dependent decreases in both the basal tonus and amplitude of neurally-evoked contractions of the lateral oviducts, and inhibited myogenic contractions. The 2-aminooxazoline, AC6 [2-(4-chloro-o-toluidino)-2-oxazoline], and the substituted phenyliminoimidazolidines (PIIs), NC5 (2,6-diethyl-PII) and NC7 (2-methyl-4-chloro-PII), were each capable of eliciting similar responses to octopamine on neurally-evoked contractions. The vertebrate alpha-adrenergic receptor antagonist phentolamine blocked the physiological effects of all agonists tested. The effect of these agonists on cyclic AMP levels was also examined. Octopamine and the three agonists were able to increase the cyclic AMP content of the lateral oviducts in a dose-dependent manner. The increases in cyclic AMP were inhibited in the presence of various vertebrate receptor antagonists. The results of this study indicate that AC6, NC5, and NC7 all act as agonists to the octopamine2-like receptors present on locust oviduct and confirm previous studies for the agonistic properties of these agents.