title: m4 muscarinic receptor subtype activates an inwardly rectifying potassium conductance in AtT20 cells.
abstract: The modulation of an inwardly rectifying potassium conductance by muscarinic receptor stimulation was studied in the AtT-20 pituitary cell line, using the whole-cell patch-clamp technique. Only m4 mRNA was detected in these cells, thus, it is assumed that the actions of muscarinic receptor stimulation are mediated by the m4 receptor. AtT-20 cells express a slowly activating inwardly rectifying potassium conductance. Application of acetylcholine (ACh), resulted in an atropine sensitive, reversible increase in inwardly rectifying current. The ACh-induced current differed from the current recorded in control, in that it was fast activating, while the control current was slowly activating. Inclusion of GTP gamma S in the patch pipette activated an inward current with characteristics similar to the ACh-induced current, and the ACh-induced current response could be inhibited by pre-incubation with pertussis toxin (PTX). It is concluded that the m4 muscarinic receptor is coupled to an inwardly rectifying potassium conductance via a PTX sensitive G-protein.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D037342:Pertussis Toxin; D010902:Pituitary Gland / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D012313:RNA / Q000096:biosynthesis; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D012313:RNA; D001285:Atropine; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000109:Acetylcholine