Muscarinic calcium mobilization in the regenerating retina of adult newt.
We used optical recording with a Ca(2+)-sensitive dye, fura2, in living slice preparations from the newt retina at different stages of regeneration. ACh produced the most pronounced [Ca2+]i rise in progenitor cells and premature ganglion cells of the earlier stage of retinal regeneration, but less pronounced Ca2+ response in ganglion cells just before, or at the beginning of, synaptogenesis. The [Ca2+]i rise to ACh was mediated by mAChRs. This was shown by inhibition of the ACh-induced Ca2+ response with a preincubation of the mAChR antagonist atropine as well as with direct stimulation of the [Ca2+]i rise by the mAChR agonist muscarine. This muscarine-induced [Ca2+]i rise was more greatly suppressed by the M1 and/or M3 preferring mAChR antagonists than by the M2 preferring mAChR antagonist. The [Ca2+]i rise due to muscarine was not suppressed in the absence of extracellular Ca2+, but suppressed in part in the presence of the L-type voltage-gated Ca2+ channel blockers, verapamil or nicardipine. Furthermore, thapsigargin (TG), a Ca-ATPase inhibitor, abolished the muscarine-induced [Ca2+]i rise in the absence of extracellular Ca2+. These results suggest that the mAChR-mediated [Ca2+]i rise is mainly a result of a release of Ca2+ from intracellular stores. TG produced a slow rise in the resting level of [Ca2+]i. This [Ca2+]i raise was suppressed as extracellular Ca2+ was omitted, whereas a rapid rise in [Ca2+]i occurred when extracellular Ca2+ was reintroduced, suggesting the occurrence of the capacitative Ca2+ influx in the progenitor cells and premature ganglion cells of the regenerating newt retina.
D000375:Aging; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology; D004347:Drug Interactions; D016257:Fura-2 / Q000378:metabolism; D066298:In Vitro Techniques; D009116:Muscarine / Q000494:pharmacology*; D018721:Muscarinic Agonists / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012455:Salamandridae
D002121:Calcium Channel Blockers; D018678:Cholinergic Agents; D018721:Muscarinic Agonists; D011976:Receptors, Muscarinic; D011189:Potassium Chloride; D009116:Muscarine; D002118:Calcium; D016257:Fura-2