Effects of biogenic amines and adrenergic drugs on oviposition in the cattle tick Boophilus: evidence for octopaminergic innervation of the oviduct.

Oviposition in the cattle tick Boophilus microplus was arrested by octopamine and the alpha-adrenergic agonists clonidine, tolazoline, and naphazoline, at doses of 25 micrograms per tick. The same effect was obtained with a sublethal dose of Amitraz of 10 micrograms per tick. In contrast, the alpha-adrenergic agonists apomorphine, synephrine, phentolamine, metaclopromide and chlorpromazine were ineffective. No mortality was observed at any of the doses tested. Reserpine, which depletes endogenous adrenergic terminals, mimicked the effects of octopamine in blocking oviposition. Acetylcholine agonists also blocked oviposition but dopaminergic agonists did not. Evidence is presented suggesting that control of the oviduct is mediated by octopaminergic receptors.