Incurvation of early embryonic neural retina by acetylcholine through muscarinic receptors.

Acetylcholine could induce the incurvation of neural retina to form a cup-structure by muscarinic receptors in vitro. Neural retinae isolated from chick embryos were cup-shaped, but, it soon became flat in a normal bath solution. Then addition of acetylcholine caused an incurvation of the retina remaking the initial cup-structure. Ca2+ was involved in this movement since a calcium ionophore A23187 could also induce the folding of neural retina. Acetylcholine caused a rise in cytoplasmic Ca2+ concentration even in a Ca(2+)-free bath solution as measured with Fura-2. Atropine completely blocked both of the Ca2+ rise and the incurvation of neural retina by acetylcholine. It was suggested that the Ca2+ mobilization from intracellular reservoirs triggered the contractile movement to fold the embryonic neural retina.