Electrophysiological and Ionic Properties of Intrinsic Circadian Pacemakers in the Vertebrate Pineal Gland
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
Document Details
- Document Type
- Technical Report
- Publication Date
- May 22, 1994
- Accession Number
- ADA280466
Entities
People
- Stuart E. Dryer
Organizations
- Florida State University