Pharmacological characterisation of voltage-dependent Ca2+ channels in isolated ganglia from the myenteric plexus

Voltage-dependent Ca2+ channels of fura-2-loaded ganglionic cells from the myenteric plexus of newborn rats were pharmacologically characterised. In contrast to completely dissociated myenteric cells, intact ganglia showed a stronger loading with the Ca2+-sensitive dye and a reproducible stimulation of the fura-2 signal by the cholinergic agonist, carbachol. A depolarisation-induced increase in the intracellular Ca2+ concentration ([Ca2+]i) was induced by superfusion with 35 mmol l− 1 KCl. This increase in [Ca2+]i was sensitive to Ni2+ and Co2+ as well as ω-conotoxin MVIIA, ω-agatoxin IVA, and SNX-482. The strongest inhibition was achieved by nifedipine (5 × 10− 7 mol l− 1) and ω-conotoxin GVIA (4.3 × 10− 7 mol l− 1). These two blockers also inhibited the [Ca2+]i increase evoked by nicotinic receptor stimulation. Consequently, isolated myenteric ganglia in culture express different types of voltage-dependent Ca2+ channels, from which the L- and the N-type seem to be the most important. When exposed to mediators of inflammation such as tumor necrosis factor-α (TNF-α) or different prostaglandins, no pronounced alterations in the fura-2 ratio were observed suggesting that changes in the Ca2+-signalling are not centrally involved in the response of enteric ganglionic cells to these paracrine substances.