Diabetes-related changes in brain beta adrenoreceptors in rats as assessed by quantitative autoradiography: relationship to hypothalamic norepinephrine metabolism and pituitary-gonadal hormone secretion.
Streptozotocin (STZ)-induced diabetes produced significant and selective alterations in brain beta adrenoreceptor subtypes, norepinephrine (NE) metabolism and pituitary-testicular hormone in male rats. The densities of beta-1 but not beta-2 adrenoreceptors were increased in hypothalamus (anterior and lateral nuclei), thalamus (ventral posterior nucleus) and amygdala (basolateral nucleus) of the STZ diabetic rats. In contrast, a decrease in the rate of metabolism of NE (estimated by the concentration of the NE metabolite, 3-methoxy-4-hydroxyphenylglycol) was observed in these STZ-treated animals. Serum concentrations of luteinizing hormone and testosterone were lower in the STZ diabetic rats. Pretreatment of rats with nicotinamide prevented the induction of hyperglycemia, upregulation of brain beta-1 adrenoreceptors, decreases in NE metabolism and reduction in serum levels of luteinizing hormone and testosterone seen in STZ-treated rats. These data suggest that derangements in the hypothalamic-pituitary-testicular axis seen in uncontrolled diabetes may be secondary to decreases in NE metabolism and compensatory upregulation of beta-1 adrenoreceptors in brain.
Bitar
M S
MS
Department of Physiological Sciences, Pennsylvania College of Podiatric Medicine, Philadelphia.
DeSouza
E B
EB
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D009536:Niacinamide / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013311:Streptozocin / Q000494:pharmacology
D006065:Gonadotropins, Pituitary; D011943:Receptors, Adrenergic, beta; D009536:Niacinamide; D013311:Streptozocin; D009638:Norepinephrine