Are there interactions between acetylcholine- and ATP-induced responses at the level of a visceral sensory ganglion?

Abstract

We investigate possible interactions between acetylcholine (ACh)- and adenosine 5′-triphosphate (ATP)-induced responses of petrosal ganglion, where the perikarya of most sensory neurons of the glossopharyngeal nerve are located. Experiments were performed on petrosal ganglia excised from pentobarbitone-anesthetized cats, desheathed and perfused in vitro. Separate applications of ACh and ATP to the exposed surface of the ganglion induced bursts of antidromic potentials recorded from the carotid (sinus) nerve branch of the glossopharyngeal nerve, which frequencies were dependent on the dose of the applied agonists. The simultaneous application of previously determined ED 50s of ACh and ATP provoked responses corresponding closely to the simple addition of the responses elicited by the separate application of each agent. Responses usually subsided within 1 min of stimuli application but were followed by periods of refractoriness to subsequent application of the same agent. After determining the timing for recovering from desensitization to the ED 50s of ACh and ATP applied separately, ACh was applied while the preparation had been desensitized to ATP and then ATP was applied during desensitization to ACh, but responses obtained were similar to control responses induced by each agent separately. In summary, ACh- and ATP-induced responses of petrosal ganglion neurons are simply additive, followed by a few minute lasting desensitization, but cross-desensitization was not observed. Thus, ACh and ATP seem to operate through independent receptors, activating separate ionic channels, whose coincident currents do not interfere each other.