Ontogenetic alterations in the effects of food and/or maternal deprivation on 5-HT, 5-HIAA and 5-HIAA/5-HT ratios.

Sprague-Dawley rat pups were deprived of food and/or the dam in experiment 1 for 24 h prior to sacrifice at 4, 10, 16 and 22 days postnatally and analysis of 5-HT, 5-HIAA and 5-HIAA/5-HT ratios in cortex, forebrain minus cortex, and brainstem. Deprivation was observed to increase indoles and their ratio early in life, with the most pronounced effects being observed in early maturing caudal brain regions of neonatal rat pups. These neurochemical effects of deprivation gradually diminished during ontogeny, becoming virtually absent by the age of weaning. In neonates, both deprivation from the dam and food appeared to influence indoleamine levels, whereas absence of food appeared to be primarily influential in older preweanling animals. Ambient temperature during the treatment period did not influence indoles or their ratio in 4- and 10-day-old rat pups, but did begin to influence indoles at 16 days postnatally, an age when homeothermia begins to develop. In experiment 2, it was observed that significant increases in indoleamines were not seen until 16 h of deprivation in 4-day-old rat pups deprived of food, and the dam for 0, 2, 4, 16 or 24 h prior to sacrifice. Possible functional implications of these deprivation-related increases in indoleamines early in ontogeny are discussed.