1. Departament of Pharmacology and Therapeutics, University Autónoma de Madrid, Madrid, Spain;2. Instituto Teófilo Hernando, University Autónoma de Madrid, Madrid, Spain;3. Facultad de Medicina, University Autónoma de Madrid, Madrid, Spain;4. Unidad de Investigación de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, México City, México;5. Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, México City, México
Abstract:
We characterized the ionic currents underlying the cellular excitability and the Ca2+‐channel subtypes involved in action potential (AP) firing of rat adrenal chromaffin cells (RCCs) preserved in their natural environment, the adrenal gland slices, through the perforated patch‐clamp recording technique. RCCs prepared from adrenal slices exhibit a resting potential of ?54 mV, firing spontaneous APs (2–3 spikes/s) generated by the opening of Na+ and Ca2+‐channels, and terminated by the activation of voltage and Ca2+‐activated K+‐channels (BK). Ca2+ influx via L‐type Ca2+‐channels is involved in reaching threshold potential for AP firing, and is responsible for activation of BK‐channels contributing to AP‐repolarization and afterhyperpolarization, whereas P/Q‐type Ca2+‐channels are involved only in the repolarization phase. BK‐channels carry total outward current during AP‐repolarization. Blockade of L‐type Ca2+‐channels reduces BK‐current ~60%, whereas blockade of N‐ or P/Q‐type produces little effect. This study demonstrates that Ca2+ influx through L‐type Ca2+‐channels plays a key role in modulating the threshold potential from RCCs in situ.