Glial fibrillary acidic protein (GFAP)-immunoreactivity is reduced by castration in the interpeduncular nucleus of male rats

THE interpeduncular nucleus of adult male rats was investigated for glial f ibrillary acidic protein immunoreactivity. In intact animals the nucleus ha d an outstandingly intense immunostaining, particularly at its periphery, i ncluding the rostral, lateral, dorsomedial and dorsolateral subnuclei where , in addition to neuropil astrocytes, a substantial amount of perivascular glia was found. Four weeks after castration, immunostaining decreased marke dly in the core region of the nucleus corresponding to the caudal and media l subnuclei, and to a much lesser extent at the periphery. The immunoreacti vity in pericapillary astrocytes proved to be insensitive to castration. Te stosterone, if administered after castration prevented or restituted the lo ss of immunoreactivity. Beyond 4 months after castration, the effect of tes tosterone gradually declined. It is concluded that testosterone stimulates the expression of glial fibrillary acidic protein immunoreactivity in the i nterpeduncular nucleus. Our findings support the argument that gonadal ster oids can influence astrocytes also in non-endocrine areas of the brain. Neu roReport 10:2229-2233 (C) 1999 Lippincott Williams & Wilkins.