INTRACELLULAR CALCIUM CHANGES ASSOCIATED WITH CHOLINERGIC NICOTINIC RECEPTOR ACTIVATION IN CULTURED MYENTERIC PLEXUS NEURONS

Intracellular free calcium concentration ([Ca2+]i) was measured in cul tured explants of myenteric plexus neurones by using the fluorescent c alcium indicator Indol in combination with patch-clamp techniques. The basal [Ca2+]i was 94 nM and spontaneous oscillations in the internal free calcium concentration were recorded. These oscillations were asso ciated with bursts of action potentials triggered by spontaneous nicot inic excitatory synaptic potentials. Under voltage clamp conditions, a pplication of the selective nicotinic agonist m-hydroxyphenylpropyltri -methylammonium iodide (10 muM) induced an inward current and increase d the intracellular free calcium concentration. We conclude that choli nergic synaptic excitatory activity provide a regular calcium entry in myenteric neurone and suggest that the nicotinic channel might be sig nificantly permeable to calcium.