Facilitation of acetylcholine secretion in mouse motor synapses caused by calcium release from depots upon activation of L-type calcium channels.

Pharmacological disinhibition of L-type Ca(2+) channels by two ways (with agonist S(-) BAY K 8644 and iberiotoxin, a Ca(2+)-activated BK-type K(+)-channel blocker) increases quantal content of evoked end-plate potentials, which was completely prevented by ryanodine (2 microM) blockade of ryanodine receptors. We conclude that increased quantal secretion of the transmitter induced by L-type Ca(2+) channel functioning requires activation of ryanodine receptors and calcium release from depots in motor terminals in mice.