An age-related decline in melatonin secretion is not altered by food restriction

Melatonin has been found to exhibit youth-maintaining and disease-preventin g properties. The current study examined whether the age-retarding regimen of chronic food restriction (FR) slowed the decline in melatonin secretion reported to occur with age. Total nocturnal melatonin secretion was assesse d by radioimmunoassay of the primary metabolite, 6-sulphatosymelatonin (6-S -OH-M LT), in urine. Measurements were made through adulthood (70 to 765 da ys) on male Wistar rats maintained on the FR regimen (60% of the normal int ake) with the control animals fed ad libitum (AL). The data of animals exhi biting gross pathology were excluded. Analyses of covariance found the FR r egimen had no effect on either the levels or pattern of decline observed in 6-S-OH-MLT excretion through adulthood. However, the FR body-weight-indexe d metabolite measures were approximately double those of the AL (p =.06). T he possibility that this result may reflect unusually high melatonin peaks in the FR tissues is discussed.