title: [The significance of extracellular Ca2+ in contractile responses in chick amnion].
abstract: Neurotransmitter receptors are formed during chick embryo development in the amnion, an avascular extraembryonic membrane devoid of innervation. Carbachol induces phasic and tonic contractions mediated by M3 cholinoceptors in an amniotic membrane strip isolated from 11-14-day-old chick embryo. The carbachol effect on the amnion contractile activity was studied in normal physiological salt solution, during depolarization by K+, exposure to nifedipine, and in calcium-free medium. Voltage-dependent and receptor-operated Ca2+ channels as well as calcium from intracellular stores are involved in the contractile response to carbachol. Phasic contractions of the amnion are mainly induced by calcium ions entering through voltage-dependent calcium channels, while tonic contractions are also maintained by receptor-operated channels. Ca(2+)-activated potassium channels can serve as a negative feedback factor in regulation of the amnion contractile responses.
authors.forename: O V
authors.initials: OV
authors.lastname: Boĭko
authors.forename: B N
authors.initials: BN
authors.lastname: Manukhin
mesh_terms: D000650:Amnion / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D020013:Calcium Signaling; D002217:Carbachol / Q000494:pharmacology; D002642:Chick Embryo; D005110:Extracellular Space / Q000378:metabolism; D015640:Ion Channel Gating; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology
chemical_list: D015220:Calcium Channels; D002217:Carbachol; D002118:Calcium