title: Cyclic GMP mimics the muscarinic response in Xenopus oocytes: identity of ionic mechanisms.
abstract: Acetylcholine (AcCho) elicits four distinct membrane responses in Xenopus oocytes; the responses can be studied by using the voltage clamp technique. The fastest of the responses, a transient inward current (D1 response), is muscarinic, being evoked by oxotremorine and blocked by atropine but not by curare or hexamethonium. The action of AcCho is cooperative, three transmitter-receptor complexes being required to cause a membrane conductance change, and the dose-response curve in most cases can be fitted by an equation assuming the existence of two binding sites with an affinity ratio of about 11. Guanosine 3',5'-cyclic monophosphate and the 8-bromo and dibutyryl derivatives cause a response similar to D1 in both its time course and the underlying ionic mechanism. The nucleotide-generated response has a smaller amplitude than the AcCho-generated D1.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002712:Chlorides; D006152:Cyclic GMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007473:Ion Channels / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects*; D010063:Ovum / Q000187:drug effects*; D011950:Receptors, Cholinergic / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*; D014982:Xenopus laevis
chemical_list: D002712:Chlorides; D007473:Ion Channels; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D001285:Atropine; D006152:Cyclic GMP; D000109:Acetylcholine