Effects of Melatonin on Hypothalamic ?3-Aminobutyric Acid, Aspartic Acid, Glutamic Acid, ?2-Endorphin and Serotonin Levels in Male Mice

摘要

>Effects of melatonin on hypothalamic neurotransmitters in male mice were studied. Exogenous melatonin administered intraperitoneally significantly increased (p < 0.05) hypothalamic concentrations of aspartic acid and ?3-aminobutyric acid by over 29 and 50% respectively. Conversely, hypothalamic ?2-endorphin concentration was significantly decreased (p < 0.05) 30 min after melatonin administration with doses between 5- and 100 ?μg/kg. Similarly, melatonin, at a concentration of 100 ?μg/kg, decreased (p < 0.05) the serotonin level in mouse hypothalamus by 46%. Melatonin, however, did not affect the concentration of hypothalamic glutamic acid over a dose range of 0.5-300 ?μg melatonin/kg. Our findings suggested that actions of pineal melatonin in animals such as inhibition on serum corticosterone levels might be mediated by the potentiation of activities of hypothalamic neurons containing ?3-aminobutyric acid and aspartic acid or by the inhibition of the ?2-endorphin and serotonin hypothalamic neurons. The neurons containing glutamic acid in the hypothalamus were, however, not influenced by melatonin. Our results are in line with the suggestion that melatonin actions on adrenal corticosterone release or other endocrine secretions may be mediated by way of its actions on hypothalamic neurotransmitter activities.