Actions of some transmitters and their antagonists on salivary secretion in a tick

Abstract
Cholinomimetics (pilocarpine, carbachol, physostigmine, acetylcholine, acetyl-.beta.-methylcholine) and sympathomimetics (dopamine, epinephrine), when injected into the hemolymph, provoked salivary fluid secretion in the female ixodid tick Amblyomma hebraeum Koch. Atropine, but not tubocurarine or toxiferine, abolished pilocarpine-induced secretion without reducing the response to dopamine. Reserpine and guanethidine likewise selectively attenuated pilocarpine-induced secretion. Following extirpation of the synganglion, pilocarpine no longer provoked a secretory response whereas dopamine did. Thus, the salivary gland appeared to be innervated directly by catecholaminergic rather than cholinergic secretory nerves. Pilocarpine probably elicited salivation by interacting with muscarinic-type cholinergic receptors situated either on the cell bodies of the secretory nerves, or alternatively, in the integrative or sensory pathway.