Mastoparan activation of dopamine-modulated K+ channels on rat striatal neurons

Coupling mechanisms between a D2-like dopamine receptor and an 85 pS K+ channel on freshly dissociated rat caudate-putamen neurons were studied using cell-attached patch-clamp electrophysiology. Channel currents were observed in the absence of dopamine receptor agonists when mastoparan, an activator of certain guanyl nucleotide binding proteins (G-proteins), was applied via the patch pipette. Channel current-voltage relationships and open probabilities observed with mastoparan were indistinguishable from those obtained with dopaminergic agonists. Alamethicin, which mimics the membrane-perturbing but not the G-protein activating properties of mastoparan, did not activate the channel, suggesting that non-specific effects of mastoparan were unlikely to account for this effect. Our results indicate that coupling between the D2 dopamine receptor and this K+ channel may involve a mastoparan-sensitive G-protein.