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Clonidine in vivo mimics the acute suppressive but not the phase‐shifting effects of light on circadian rhythm of serotonin N‐acetyltransferase activity in chick pineal gland
Author(s) -
Zawilska Jolanta B.
Publication year - 1994
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1994.tb00115.x
Subject(s) - circadian rhythm , endocrinology , medicine , pineal gland , melatonin , serotonin , biology , light effects on circadian rhythm , darkness , in vivo , endocrine gland , agonist , receptor , suprachiasmatic nucleus , hormone , botany , microbiology and biotechnology
Zawilska JB. Clonidine in vivo mimics the acute suppressive but not the phase‐shifting effects of light on circadian rhythm of serotonin N‐acetyltransferase activity in chick pineal gland. J. Pineal Res. 1994; 17: 63–68. ©Munksgaard, 1994 Abstract Comparative in vivo studies on effects of pulses of light and clonidine, a selective agonist of α 2 ‐adrenergic receptors, on the circadian rhythm of serotonin N‐acetyltransferase (NAT) activity in chick pineal gland were performed. Six‐hour pulses of white light caused an acute suppression of the nocturnal NAT activity and phase‐dependent phase shifts of the circadian rhythm of the enzyme activity relative to controls. Systemic administration of clonidine acutely suppressed NAT activity of chick pineal gland, but did not affect the phase of subsequent cycles in constant darkness. These results give further support to the concept based on in vitro studies that α 2 ‐adrenergic receptors are involved in regulation of melatonin biosynthesis in chick pineal gland by a mechanism distal to the pacemaker that generates the circadian melatonin rhythm.