Pharmacological characterization of alpha adrenoceptor-mediated motor responses in the rat colon.

Background: Inhibitory neuromuscular transmission in the gastrointestinal tract is mediated by intrinsic nitrergic and purinergic neurons. Purines activate G protein-coupled receptor P2Y receptors, increasing intracellular Ca that activates small conductance calcium-activated potassium (SK) channels. Little is known about the effect of adrenergic receptor activation on intestinal smooth muscle.