Potassium conductance increased by noradrenaline, opioids, somatostatin, and G-proteins: Whole-cell recording from guinea pig submucous neurons

Agonists at α₂-adrenoceptors, δ-opioid receptors, and somatostatin receptors were applied to dissociated guinea pig submucous plexus neurons; whole-cell recordings of membrane current showed that they increased the membrane potassium conductance. The conductance affected showed inward rectification, being described by G_ag(max)/{1 + exp((V - V_0.5)/k)} where V_0.5 was about -65 mV and G_ag(max) was about 10 nS. The agonists were ineffective when the potassium conductance of the neurons had first been increased by intracellular dialysis with purified guanosine 5′-triphosphate (GTP)-binding proteins (G_i or G_o). Agonist actions were prevented by pertussis toxin, applied intracellularly (10-100 ng/ml for several minutes) or extracellularly 1-10 μg/ml for 1 hr); in the latter case, the agonist responses were reconstituted by intracellular dialysis with GTP-binding proteins.