Neural and endocrine development after chronic tryptophan deficiency in rats: I. Brain monoamine and pituitary responses.

Caloric restriction and tryptophan deficient diets have been shown to delay aging in the immature laboratory rat. Studies of monoamine levels in the brain of developing female rats fed on these diets show changes in serotonin but not norepinephrine or dopamine levels: in tryptophan-restricted rats serotonin levels were reduced in all brain areas studied, whereas in caloric-restricted animals serotonin levels were increased in the cerebral hemispheres only. Another group of animals, in which growth and maturation was delayed by feeding d,1-parachlorophenylalanine (PCPA) showed decreases in serotonin, norepinephrine and dopamine concentrations in all brain regions investigated. All treatments employed to arrest growth and maturation resulted in pituitary alterations manifested by gross, histological and ultrastructural changes. It is postulated that there maturation- and age-retarding treatments delay the development of the central nervous system resulting in postponed maturation of the neuroendocrine axis, with consequent hypoactivity of certain pituitary functions and a resultant delay in the onset of maturation and senescence.