γ-Aminobutyric acid (GABA)B receptors couple to Go to inhibit N-type calcium channels in embryonic chick dorsal toot ganglion neurons1. The voltage-independent inhibition, mediated by means of a tyrosine-kinase pathway2, is transient and lasts up to 100 seconds. Inhibition of endogenous RGS12, a member of the family of regulators of G-protein signalling, selectively alters the time course of voltage-independent inhibition. The RGSI2 protein, in addition to the RGS domain, contains PDZ and PTB domains3. Fusion proteins containing the PTB domain of RGS12 alter the rate of termination of the GABAB signal, whereas the PDZ or RGS domains of RGS12 have no observable effects. Using primary dorsal root ganglion neurons in culture, here we show an endogenous agonist-induced tyrosine-kinase-dependent complex of RGS12 and the calcium channel. These results indicate that RGS12 is a multifunctional protien capable of direct interactions through its PTB domain with the tyrosine-phosporylated calcium channel. Recruitment of RGS protiens to G-protien effectors may represent an additional mechanism for signal termination in G-protien effectors may represent an additional mechanism for signal termination in G-protien-coupled pathways.