These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Norepinephrine stimulates potassium efflux from pinealocytes: evidence for involvement of biochemical "AND" gate operated by calcium and adenosine 3',5'-monophosphate.
    Author: Ceña V, Halperin JI, Yeandle S, Klein DC.
    Journal: Endocrinology; 1991 Jan; 128(1):559-69. PubMed ID: 1846112.
    Abstract:
    Biochemical studies of K+ efflux from rat pinealocytes revealed for the first time that norepinephrine (NE) increases 86Rb+ and 42K+ efflux. The effects of NE depend upon concurrent activation of both alpha 1- and beta-adrenoceptors. This effect is mediated by cAMP and Ca2+, which appear to act in conjunction to control K+ efflux; studies with charybdotoxin and tetraethylammonium indicate that a Ca2(+)-sensitive K+ channel (K(Ca] appears to be involved. Patch clamp studies identified a large conductance (approximately 100 psec) K+ channel. This study also revealed for the first time that NE treatment increases the fraction of time that this channel was open. Studies of inside-out pineal membrane patches indicated that increasing Ca2+ at the cytoplasmic surface of the membrane increased the frequency of channel opening, as is typical of K(Ca) channels in this type of preparation. Outward K+ currents were almost completely blocked by tetraethylammonium (10 mM) and scorpion venom (L. quinquestriatum; 100 ng/ml). Cell-attached studies confirm that the effects of NE are mediated by intracellular second messengers. These investigations suggest that NE elevates K+ flux, probably through a large conductance K(Ca) channel, that NE acts through alpha 1- and beta-adrenergic receptors, and that Ca2+ and cAMP act together through a biochemical "AND" gate to mediate the effects of receptor activation. Activation of this K(Ca) channel would have a hyperpolarizing influence and might contribute to the adrenergic hyperpolarization of pinealocytes.
    [Abstract] [Full Text] [Related] [New Search]