AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 2 371-R380, Copyright © 1986 by American Physiological Society
Effects of dietary protein and tyrosine on behavior of diabetic rats
L. L. Bellush and N. E. Rowland
Streptozotocin-diabetic and nondiabetic control male rats were fed
synthetic diets varying in macronutrient content (experiment 1) or diets
with or without added tyrosine (experiments 2 and 3). All rats were
evaluated for stereotyped behaviors after administration of apomorphine (1
mg/kg) and amphetamine (3 and 5 mg/kg). At the end of experiments 2 and 3,
rates of tyrosine hydroxylation in hypothalamus, nucleus accumbens, and
striatum were determined by measuring L-3,4-dihydroxyphenylalanine
concentrations after decarboxylase inhibition. In experiment 3 the ratios
of tyrosine to dopamine were also measured in striatum and nucleus
accumbens. Diabetic rats fed a standard high-carbohydrate diet showed
decreased stereotypy relative to controls. Neither systematic alterations
of fat or protein content of the diet nor selective tyrosine enrichment
affected this attenuation of stereotypy in diabetics.
L-3,4-dihydroxyphenylalanine concentration in nucleus accumbens was
increased by dietary tyrosine enrichment in experiment 2 but not in
experiment 3. However, brain tyrosine levels were elevated in rats fed
tyrosine-enriched diets. These results argue against a significant
contribution of precursor elevation to catecholamine function and behavior
in experimental diabetes.
