title: Intracellular Ca2+ signaling pathway is involved in light-induced phase advance, but may not be in phase delay, of the circadian melatonin rhythm in chick pineal cell.
abstract: Chick pineal cells have photoreceptive, circadian clock and melatonin synthetic capacities, and express circadian oscillation of melatonin release in vitro. Light pulses cause phase-dependent phase shift of the melatonin rhythm. The purpose of this study was to address the questions whether intracellular calcium is involved in both light-induced phase advance and delay. Thapsigargin and cyclopiazonic acid, which deplete the intracellular calcium stores, blocked the light-induced phase advance in a dose-dependent manner. The pulses of ryanodine receptor antagonist (dantrolene sodium or ruthenium red) also blocked the light-induced phase advance. Most agents did not cause a significant phase shift by themselves. On the other hand, all the agents used, failed to block the light-induced phase delay, even if the magnitude of phase delay was decreased using low intensity light. An antagonist of nitric oxide synthase blocked neither light-induced phase advance nor phase delay. These results indicate the following possibilities: (1) the mechanism of light-induced phase advance and delay may be different in chick pineal cells, or (2) if intracellular calcium is involved in both light-induced phase advance and delay, the sensitivity to light and/or agents used in this study may differ according to Zeitgeber time.
authors.affiliation: Department of Veterinary Physiology, Faculty of Agriculture, University of Miyazaki, Japan. a0d209u@cc.miyazaki-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Nakahara
authors.forename: N
authors.initials: N
authors.lastname: Murakami
authors.forename: E
authors.initials: E
authors.lastname: Takigami
authors.forename: T
authors.initials: T
authors.lastname: Nasu
authors.forename: T
authors.initials: T
authors.lastname: Murakami
authors.forename: K
authors.initials: K
authors.lastname: Shiota
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000528:radiation effects; D002645:Chickens / Q000502:physiology*; D002940:Circadian Rhythm / Q000187:drug effects / Q000528:radiation effects; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008027:Light; D008550:Melatonin / Q000378:metabolism*; D017440:Photoperiod; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D007211:Indoles; D019284:Thapsigargin; D008550:Melatonin; C000543:cyclopiazonic acid