Age-related changes in the thermoregulatory capacity of tryptophan-deficient rats

From a larger study seeking to develop indexes of physiological aging, the present experiment was designed 1) to test thermoregulatory capacity in the aging and old rat subjected to 3 minutes of whole-body ice water immersion, and 2) using this index of physiological age, to determine whether tryptophan deficiency from time of weaning can retard the onset of senescence. Results indicate a progressive prolongation of temperature recovery time from young to middle age to old, and tryptophan-deficient animals restored to commercial diet at middle age show the thermoregulatory capacity of young adults. The implications of tryptophan deficiency with respect to brain development, serotonin metabolism, and temperature regulation are also discussed in terms of the possibility of intervening with the aging process.