MUSCARINIC M-CURRENT INHIBITION VIA G(ALPHA-Q 11) AND ALPHA-ADRENOCEPTOR INHIBITION OF CA2+ CURRENT VIA G(ALPHA-O) IN RAT SYMPATHETIC NEURONS/

1. Microinjection of selective antibodies into superior cervical gangl ion (SCG) neurones has identified the G-protein alpha-subunits mediati ng muscarinic receptor inhibition of M-type K+ current (I-K(M)) and al pha-adrenoceptor inhibition of Ca2+ current (I-Ca). 2. Antibodies spec ific for G(alpha q/11), but not those for G(alpha 0), reduced M-curren t inhibition by the muscarinic agonist oxotremorine-M, whereas anti-al pha 0 antibodies, but not anti-G(alpha q/11) or anti-G(alpha 11-3) ant ibodies, reduced calcium current inhibition by noradrenaline. 3. Immun oblots with specific anti-G-protein antibodies demonstrated the presen ce of both G(alpha q) and G(alpha 11) while G(alpha 01) (but virtually no G(alpha 02)) was present. 4. We conclude that M(1) muscarinic rece ptor inhibition of I-K(M) is transduced by G(alpha q) and/or G(alpha 1 1) and that G(alpha 0) transduces alpha-adrenoceptor inhibition of I-C a.