Preliminary Observations on the Suppression of Nocturnal Plasma Melatonin Levels by Short-Term Administration of Diazepam in Humans
Article first published online: 30 JAN 2007
Journal of Pineal Research
Volume 6, Issue 3, pages 253–258, July 1989
How to Cite
Monteleone, P., Forziati, D., Orazzo, C. and Maj, M. (1989), Preliminary Observations on the Suppression of Nocturnal Plasma Melatonin Levels by Short-Term Administration of Diazepam in Humans. Journal of Pineal Research, 6: 253–258. doi: 10.1111/j.1600-079X.1989.tb00421.x
- Issue published online: 30 JAN 2007
- Article first published online: 30 JAN 2007
- Received May 16, 1988; accepted August 8, 1988.
Several studies suggest that GABAergic mechanisms may be involved in the modulation of melatonin secretion. However, conflicting results have been reported in animal studies; in humans the issue has not been widely investigated. In the present study, using a double-blind design, six healthy men received orally, at midnight, 10 mg of diazepam, a GABAergic agent, or placebo, on two different occasions 1 week apart. Blood samples were collected, in the dark, immediately before the drug administration, and at 12:30, 1, 2, 3, and 4 AM. Serum melatonin was measured by a radioimmunological method with [125I]melatonin as a tracer. Two-way ANOVA with repeated measurements disclosed a significant effect for treatment (P < 0.01), for time (P < 0.0004), and for treatment X time interaction (P < 0.05). Following diazepam administration, serum melatonin levels observed at 2, 3, and 4 AM were significantly lower than the corresponding values following placebo (P < 0.02 at 2 and 4 AM; P < 0.03 at 3 AM [Students' paired t test]). These results show that nocturnal blood melatonin levels may be suppressed by the acute administration of a GABAergic agent, suggesting that GABA may be involved in the modulation of pineal activity in man.