alpha 2 and alpha 1-Adrenoceptors mediate opposing actions on parasympathetic neurons.
We used intracellular recording methods to analyze the membrane responses to norepinephrine in cat vesical parasympathetic ganglia. In parasympathetic neurons, norepinephrine (NE) produces a membrane hyperpolarization, a membrane depolarization often accompanied by cell firing and a biphasic potential, a hyperpolarization followed by a depolarization. We found that the NE hyperpolarization is mediated through alpha 2-adrenoceptors while the NE depolarization is mediated through alpha 1-adrenoceptors. This situation is different than in sympathetic neurons where beta-adrenoceptors mediate a NE depolarization.
D000818:Animals; D002415:Cats; D003000:Clonidine / Q000494:pharmacology; D004347:Drug Interactions; D005726:Ganglia, Parasympathetic / Q000502:physiology*; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D001743:Urinary Bladder / Q000294:innervation*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine