Open AccessCyclic GMP mimics the muscarinic response in Xenopus oocytes: identity of ionic mechanisms.
Author(s) -
Nathan Dascal,
Emmanuel M. Landau
Publication year - 1982
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.79.9.3052
Subject(s) - oxotremorine , muscarinic acetylcholine receptor , xenopus , hexamethonium , biophysics , acetylcholine , voltage clamp , reversal potential , chemistry , membrane potential , endocrinology , atropine , medicine , biology , receptor , biochemistry , patch clamp , gene
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.