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 [Ca(2+)](i) rise in progenitor cells and premature ganglion cells of the earlier stage of retinal regeneration, but less pronounced Ca(2+) response in ganglion cells just before, or at the beginning of, synaptogenesis. The [Ca(2+)](i) rise to ACh was mediated by mAChRs. This was shown by inhibition of the ACh-induced Ca(2+) response with a preincubation of the mAChR antagonist atropine as well as with direct stimulation of the [Ca(2+)](i) rise by the mAChR agonist muscarine. This muscarine-induced [Ca(2+)](i) rise was more greatly suppressed by the M1 and/or M3 preferring mAChR antagonists than by the M2 preferring mAChR antagonist. The [Ca(2+)](i) rise due to muscarine was not suppressed in the absence of extracellular Ca(2+), but suppressed in part in the presence of the L-type voltage-gated Ca(2+) channel blockers, verapamil or nicardipine. Furthermore, thapsigargin (TG), a Ca-ATPase inhibitor, abolished the muscarine-induced [Ca(2+)](i) rise in the absence of extracellular Ca(2+). These results suggest that the mAChR-mediated [Ca(2+)](i) rise is mainly a result of a release of Ca(2+) from intracellular stores. TG produced a slow rise in the resting level of [Ca(2+)](i). This [Ca(2+)](i) raise was suppressed as extracellular Ca(2+) was omitted, whereas a rapid rise in [Ca(2+)](i) occurred when extracellular Ca(2+) was reintroduced, suggesting the occurrence of the capacitative Ca(2+) influx in the progenitor cells and premature ganglion cells of the regenerating newt retina. (C) 2003 Elsevier B.V. All rights reserved.