COLOCALIZATION OF ANDROGEN RECEPTOR AND NITRIC-OXIDE SYNTHASE IN THE VENTRAL PREMAMMILLARY NUCLEUS OF THE NEWBORN RAT - AN IMMUNOHISTOCHEMICAL STUDY

The distribution of the neuronal nitric oxide synthase (nNOS), androge n receptor (AR), estrogen receptor (ER) and aromatase (ARO) was studie d in the dorsal and ventral premammillary nuclei (PMd and PMv) of the newborn rat by immunohistochemistry. In the intact male pups, nNOS imm unoreactivity (-IR) was present both in the PMd and the PMv, while AR- IR was detected only in the PMv. On the other hand, ER-IR and ARO-IR w ere scarcely encountered in the both PMd and PMv. By double immunostai ning of nNOS and AR, all the nNOS-IR cells in the PMv were revealed to contain AR-IR. In the intact female pups, nNOS-IR was present in the both PMd and PMv, but neither ER-, nor ARO-LR were detected in the PM region. In the PMv of the intact female rat, no AR-IR was detected at 6 days of age, while it was detected as only a faint staining within 1 2 h after birth. When the male pups were castrated neonatally, no AR-I R was detected in the PMv. Subcutaneous injections of Scr-dihydrotesto sterone (DHT) induced strong AR-IR in the castrated male and the intac t female pups. On the contrary, the intensity of nNOS-IR stayed unchan ged among these animals. Neonatal androgen and nitric oxide has been c onsidered important to brain development. Moreover, involvement of the PMv in aggressive and mating behavior of male animals has been report ed. Together with the fact that the AR-IR and nNOS-IR were found in th e same neurons in the PMv, involvement of this nucleus in masculinizat ion of the brain by non-aromatizable androgen is postulated. (C) 1997 Elsevier Science B.V.