Melatonin in mice: rhythms, response to light, adrenergic stimulation

renergic stimulation, and metabolism. Am J Physiol Regula-tory Integrative Comp Physiol 282: R358–R365, 2002; 10.1152/ajpregu.00360.2001.—There has been relatively lit-tle research conducted on pineal melatonin production in laboratory mice, in part, due to the lack of appropriate assays. We studied the pineal and plasma rhythm, response to light, adrenergic stimulation, and metabolism of melato-nin in CBA mice. With the use of a sensitive and specific melatonin RIA, melatonin was detected in the pineal glands at all times of the day21 fmol/gland in CBA mice but not in C57Bl mice. Both plasma and pineal melatonin levels peaked 2 h before dawn in a 12:12-h light-dark photoperiod (162 31 pM and 1,804 514 fmol/gland, respectively). A brief light pulse (200 lx/15 min), 2 h before lights on, suppressed both plasma and pineal melatonin to near basal levels within 3