Effects of melatonin ingestion on cAMP and cGMP levels in human plasma.
The effects of daytime melatonin treatment (0.3 mg) on cAMP and cGMP levels in platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were investigated in 14 normal human subjects (age+/-s.e.m. 26.2+/-3. 2 years). Plasma levels of cAMP, cGMP and melatonin were measured before and at intervals for 3 h after the treatment was administered at 1300 h. Plasma melatonin concentrations reached peak levels 1 h after the treatment (mean+/-s.d. 182.3+/-43.5 pg/ml). The mean areas under the curve (AUC) for the time-cGMP concentration curves in PPP and in PRP were significantly increased after melatonin treatment compared with those observed after placebo treatment (P=0.001). No significant difference in cGMP levels was observed between PPP and PRP. Increase in self-reported sleepiness after melatonin treatment positively correlated with increase in plasma cGMP levels (r=0.92). The mean AUC for the time-cAMP concentration in PRP, but not in PPP, was increased 1 h after melatonin treatment compared with that observed after placebo treatment, but not thereafter. No correlation between individual PRP or PPP cAMP levels and subjective sleepiness was observed. These results demonstrate a stimulating effect of melatonin treatment on plasma cGMP levels in humans and suggest a correlation between the increase in circulating cGMP levels and the sleep-promoting effect of the pineal hormone.
Zhdanova
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IV
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. zhdanova@mit.edu
Raz
D J
DJ
D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D001792:Blood Platelets; D000242:Cyclic AMP / Q000097:blood*; D006152:Cyclic GMP / Q000097:blood*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D012894:Sleep Stages / Q000187:drug effects; D013268:Stimulation, Chemical
D000242:Cyclic AMP; D006152:Cyclic GMP; D008550:Melatonin