Muscarinic M‐current inhibition via G alpha q/11 and alpha‐adrenoceptor inhibition of Ca2+ current via G alpha o in rat sympathetic neurones.


1. Microinjection of selective antibodies into superior cervical ganglion (SCG) neurones has identified the G‐protein alpha‐subunits mediating muscarinic receptor inhibition of M‐type K+ current (IK(M)) and alpha‐adrenoceptor inhibition of Ca2+ current (ICa). 2. Antibodies specific for G alpha q/11, but not those for G alpha o, reduced M‐current inhibition by the muscarinic agonist oxotremorine‐M, whereas anti‐G alpha o antibodies, but not anti‐G alpha q/11 or anti‐G alpha i1‐3 antibodies, reduced calcium current inhibition by noradrenaline. 3. Immunoblots with specific anti‐G‐protein antibodies demonstrated the presence of both G alpha q and G alpha 11, while G alpha o1 (but virtually no G alpha o2) was present. 4. We conclude that M1 muscarinic receptor inhibition of IK(M) is transduced by G alpha q and/or G alpha 11, and that G alpha o transduces alpha‐adrenoceptor inhibition of ICa. © 1994 The Physiological Society