Figure 6. Schematic diagram of the cholinergic nerve ending-chromaffin cell synapse in the adrenal gland of rat.

This diagram demonstrates possible localizations of voltage-dependent Ca²⁺ channels and cholinergic receptors mediating adrenal catecholamine secretion. Adrenaline-containing cells possess synaptic nicotinic receptors, extrasynaptic nicotinic and muscarinic receptors, and L-type voltage-dependent Ca²⁺ channels close to the extrasynaptic nicotinic receptors. Noradrenaline-containing cells possess L-type voltage-dependent Ca²⁺ channels close to synaptic nicotinic receptors. P/Q-type voltage-dependent Ca²⁺ channels are located on cholinergic nerve endings.