Contraction wave in the chick blastoderm induced by muscarinic stimulation

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Abstract
The mechanism of excitation contraction coupling during morphogenetic movements is unknown. We describe a contraction wave in the chick blastoderm after muscarinic stimulation, which indicates that an autocrine cholinergic mechanism might be involved in the induction of morphogenetic movements during embryogenesis. Chick blastoderms were explanted in a modified new culture and the cellular movements were recorded by time lapse video filming. Perfusion with acetylcholine or carbachol induced a contraction wave in the blastoderm which started in the periphery at the point of entrance of the drug, and proceded within 8–10 min through the area pellucida to the opposite side of the blastoderm. Perfusion with the muscarinic antagonist pilocarpine in turn induced relaxation. Atropine inhibited the effect of the agonists acetylcholine and carbachol. From earlier studies we know that in the chick embryo a muscarinic system is present, the expression of which correlates with morphogenetic movements. The induction of a contraction wave in the chick blastoderm by muscarinic agonists supports our hypothesis that embryonic cell movements might be regulated via muscarinic receptors.