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Melatonin potentiates 5‐HT 1A receptor activation in rat hypothalamus and results in hypothermia
Author(s) -
Lin MaoTsun,
Chuang JihIng
Publication year - 2002
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 - 10.1034/j.1600-079x.2002.01867.x
Subject(s) - melatonin , medicine , endocrinology , hypothermia , thermoregulation , serotonin , agonist , hypothalamus , 5 ht receptor , antagonist , chemistry , receptor antagonist , receptor , pindolol , melatonin receptor
Effects of melatonin on both thermoregulatory responses and hypothalamic serotonin release were assessed in unanesthetized rats at three different ambient temperatures ( T a ). Systemic administration of melatonin (30–120 mg/kg, i.p) caused a decrease in both colonic temperature and hypothalamic serotonin (5‐HT) release in rats at both T a 8 and 22°C. The hypothermia was brought about by a decrease in metabolic rate at T a 8°C, whereas at T a 22°C the hypothermia was produced by both a decrease in metabolic rate and an increase in cutaneous temperature. However, in the heat ( T a 31°C), neither thermoregulatory responses nor hypothalamic 5‐HT release was affected by the same amount of administered melatonin. The melatonin‐induced hypothermia and decreased 5‐HT release in the hypothalamus were attenuated by selective depletion of brain 5‐HT produced by intracerebroventricular injection of 5,7‐dihydroxytryptamine. Furthermore, the melatonin‐induced hypothermia was almost completely abolished by treatment with a 5‐HT 2A receptor agonist (DOI) or a 5‐HT 1A receptor antagonist [(−)‐pindolol]. The data indicate that melatonin potentiates the 5‐HT 1A receptor activation in the hypothalamus and results in hypothermic effects which can be antagonized by the expected hyperthermic effect of DOI.