Melatonin

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  melatonin \mel`a*tonin\ n. (Physiology)
     A hormone secreted by the pineal gland. Chemically it is
     N-acety-5-methoxytryptamine. Research has indicated that
     there are daily rhythms in secretion of melatonin, in
     particular due to the depressing effect on melatonin
     production by light received by the retina. Conversely it


     appears that melatonin may influence the circadian rhythms of
     animals. There is some experimental evidence that
     administration of melatonin may increase the amount of sleep
     in people with sleep disorders. However, the evidence is not
     convincing and the effect is not profound. Nevertheless, the
     deregulation of melatonin and its availability
     over-the-counter has led to many people taking melatonin to
     help sleep, without consulting a physician.
     [WordNet 1.5 +PJC]
  
           A role for melatonin in sleep facilitation has been
           inferred from its effect on electroencephalogram
           patterns, but it has not been possible to demonstrate
           that wakefulness sleep cycles are driven by periodic
           accumulation, depletion, or regeneration of melatonin.
                                                    --Uwe
                                                    Ackermann,
                                                    Essentials of
                                                    Human
                                                    Physiology,
                                                    1992

From WordNet (r) 2.0 [wn]:

  melatonin
       n : hormone secreted by the pineal gland