Accession Number:

ADA280466

Title:

Electrophysiological and Ionic Properties of Intrinsic Circadian Pacemakers in the Vertebrate Pineal Gland

Descriptive Note:

Annual technical rept. 1 Apr 1993-31 Mar 1994

Corporate Author:

FLORIDA STATE UNIV TALLAHASSEE

Personal Author(s):

Report Date:

1994-05-22

Pagination or Media Count:

7.0

Abstract:

Cyclic GMP-activated channels of the chick pineal gland are not altered by physiological concentrations of cytoplasmic Ca2 ions. They are partially blocked by physiological levels of Mg2. Changes in intracellular pH over a range of 6.2-8.2 do not affect the gating of these channels. Chick pineal cells exhibit spontaneous oscillations in intracellular free Ca2 and can mobilize intracellular Ca2 stores. Agents that increase intracellular cyclic AMP cause increases in intracellular Ca2. Similar effects are caused by VIP but not norepinephrine. Depletion of intracellular stores causes release of a message that promotes influx of Ca2 from the outside. Internal stores of Ca2 represent a potential target for the intrinsic circadian oscillator. Inhibition of phosphodiesterases cause activation of cyclic GNP-activated channels in the whole pineal cell, suggesting that photo-transduction cascades similar to those of the vertebrate retina are also present in chick pineal cells. A second large- conductance cation channel has also been detected an may play a role in spontaneous or drug-induced Ca2 oscillations

Subject Categories:

  • Anatomy and Physiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE