Ontogeny of the levels of biogenic amines in various parts of the brain and in peripheral tissues in normal and protein malnourished rats

Abstract

The ontogenetic development of serotonin, 5-hydroxyindoleacetic acid, and norepinephrine in brain regions and in peripheral tissues was examined in normal and protein malnourished rats from birth to age 300 days. The malnourished rats, which received a diet low in protein starting 5 weeks prior to conception, showed significantly elevated brain and peripheral tissue levels of the biogenic amines and 5-hydroxyindoleacetic acid at birth. This is one of the earliest ages at which protein malnutrition has been reported to affect a major biochemical measure in the brain. In malnourished rats, brain concentrations of serotonin and 5-hydroxydoleacetic acid remained elevated at older ages, up to 300 days, with the largest effects (up to 200% increase) occurring in subtelencephalic brain regions. These changes in brain indole levels probably represent a general metabolic alteration of indoleamine metabolism since elevated indole concentrations were also observed in the heart, lung, and stomach. At most ages the increase in brain norepinephrine levels in malnourished rats was less pronounced than for the indoles. Also, no increase in norepinephrine concentration in the peripheral tissues were observed. With respect to norepinephrine concentrations, the brain appears to be more sensitive to the insult of protein malnutrition than do peripheral tissues. The present results demonstrate that rearing rats on a diet low in protein, but adequate in all other respects, significantly elevates the brain amine content at most ages from birth through 300 days of age.