Action potential stimulation reveals an increased role for P/Q-calcium channel-dependent exocytosis in mouse adrenal tissue slices

• DOI: 10.1016/j.abb.2004.12.005
• Publication Date: 2004-12-24T10:45:12Z
• Authors: Shyue-An Chan; Luis Polo-Parada; Corey Smith
• Keywords: Chromaffin cell; Cardiac action potential

Chromaffin cells of the adrenal medulla receive cholinergic input from the splanchnic nerve. Upon sympathetic activity, chromaffin cells fire action potentials that open voltage-gated calcium channels and evoke the exocytic release of catecholamines. Catecholamines then regulate homeostatic processes such as cardiac output and vascular tone. Thus control of the Ca(2+) influx in chromaffin cells represents a target for the regulation of multiple physiological functions. Previous reports utilized square pulse depolarizations to quantify the proportional exocytic response as a function of Ca(2+) channel subtype. In this study, we use perforated patch voltage clamp and action potential waveforms to depolarize cells in situ. We analyze Ca(2+) current components under conditions that match the dynamic native cell behavior. This approach revealed a greater role for P/Q-type calcium channels in evoked exocytosis than previously reported. Thus, the P/Q-type channels represent a more important control point for the regulation of catecholamine-dependent processes than previously believed.