CATECHOLAMINES AND TYROSINE-HYDROXYLASE EXPRESSION IN THE HYPOTHALAMUS OF NEONATALLY OVERNOURISHED WEANLING RATS

Catecholamines are important organizers of the developing brain. Durin g life, they are involved, e.g., in the regulation of body weight and metabolism by hypothalamic nuclei which are suggested to be highly vul nerable to malorganization by alterations of perinatal metabolism, as in early postnatal overnutrition. By reducing the litter size on the 3 rd day of life (small litters, SL) early postnatal overnutrition was i nduced in Wistar rats. SL rats developed overweight (p < 0.001), assoc iated with increased plasma insulin on the 21st day of life (p < 0.01) . Using HPLC with ECD, catecholamines in various hypothalamic nuclei w ere determined, and quantitative immunocytochemistry for tyrosine hydr oxylase (TH) was performed. In the 21-day-old SL rats, norepinephrine ((NE) was significantly increased in the paraventricular hypothalamic nucleus (PVN), while a significant decrease of dopamine (DA) appeared in the ventromedial hypothalamic nucleus (VMN). In the PVN of SL rats, this was accompanied by a reduction of the mean numerical density of neurons in general (p < 0.05) and an increased numerical density of ne urons expressing TH (p < 0.05). Both parameters were unchanged within the periventricular hypothalamic area (PER). These data suggest specif ic disturbances of catecholaminergic systems within hypothalamic regul ators of body weight and metabolism during development due to early po stnatal overnutrition in rats.