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 omega-conotoxin MVIIA, omega-agatoxin IVA, and SNX-482. The strongest inhibition was achieved by nifedipine (5 x 10(-7) mol l(-1)) and omega-conotoxin GVIA (4.3 x 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-alpha (TNF-alpha) 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.
Institut für Veterinär-Physiologie, Justus-Liebig-Universität Giessen, Frankfurter Str. 100, D-35392 Giessen, Germany.
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Diener
D000818:Animals; D000831:Animals, Newborn; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D016257:Fura-2; D005725:Ganglia, Autonomic / Q000187:drug effects / Q000378:metabolism*; D009197:Myenteric Plexus / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011950:Receptors, Cholinergic / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D011950:Receptors, Cholinergic; D002217:Carbachol; D016257:Fura-2