Alpha 1-adrenergic receptor activation depolarizes rat supraoptic neurosecretory neurons in vitro.
Intracellular data were obtained from 35 supraoptic nucleus neurosecretory neurons maintained in vitro in intra-arterially perfused explants of rat hypothalamus. Addition of norepinephrine, phenylephrine, or methoxamine, but not isoproterenol (30-200 microM), consistently induced membrane depolarization, bursting activity, and an associated prolongation in action potential duration, effects that were reversibly antagonized by the alpha 1-antagonist prazosin. Norepinephrine-evoked depolarizations demonstrated no consistent change in membrane resistance and were reduced both by membrane hyperpolarization and by raising extracellular K+. Norepinephrine shortened the time course of spike hyperpolarizing afterpotentials and increased the magnitude of late depolarizing afterpotentials. It is proposed that one of norepinephrine's actions on supraoptic neurons involves K+ channels, perhaps by modulation of a transient K+ current known as A current.
D000200:Action Potentials / Q000187:drug effects; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009490:Neurosecretory Systems / Q000166:cytology / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013495:Supraoptic Nucleus / Q000166:cytology / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D009638:Norepinephrine