Testosterone inhibition of tyrosine hydroxylase expression in the hypothalamic arcuate nucleus.
Immunohistochemistry was used to detect tyrosine hydroxylase (TH)-containing neurons in the hypothalamic arcuate nucleus in male rats. Two weeks following castration, the number of TH-positive cells was significantly greater than in intact controls. The castration-responsive TH-positive cells were uniformly distributed throughout the mediolateral extent of the arcuate nucleus. Treatment with testosterone significantly suppressed the castration response, whereas neither estradiol nor 5 alpha-dihydrotestosterone were effective. The number of TH-positive arcuate neurons in the female was similar to that in the male. Ovariectomy did not affect the number of TH-positive neurons. These findings indicate that TH expression is tonically inhibited in the tuberoinfundibular dopaminergic system of the male rat by testosterone.
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000201:enzymology*; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D008297:Male; D009919:Orchiectomy; D010052:Ovariectomy; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013739:Testosterone / Q000494:pharmacology*; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D013196:Dihydrotestosterone; D013739:Testosterone; D004958:Estradiol; D014446:Tyrosine 3-Monooxygenase