Neuropeptides are central to the regulation of mammalian gender-dependent development and reproduction. Preoptic regulatory factor-2 is a neuropeptide gene that is known to be expressed in rat brain and testis. In the brain, expression is gender-dependent and age-dependent. Tissue-specific transcripts are found in the preoptic area (POA) of the hypothalamus and in the testis. In order to investigate the effects of reproductive hormone status on expression of porf-2 in the male rat, porf-2 transcripts were studied by Northern blot analysis in intact, hypophysectomized, and castrated rat POA, medial basal hypothalamus (MBH), cerebral cortex (CC), testis, and liver. Castration of hypophysectomy increased levels of the brain-specific 0.84 kb 5' porf-2 transcript in the POA, but did not affect levels of this transcript in the CC. There was a small decrease in the MBH following castration. Hypophysectomy also resulted in a fourfold increase in the 5' 1.1 kb testis-specific transcript. The affected transcripts are localized to the cytoplasm. A nontissue specific 3' transcript was also detected. Interestingly, this 0.6 kb transcript became non-detectable in all tissues examined following hypophysectomy. Porf-2 mRNA was also detected in human hypothalamus, testis, adrenal, placenta, and prostate with unique transcripts in each tissue examined . It has been shown elsewhere that porf-2 is a unique single copy gene in the rat genome. These data demonstrate that expression of the porf-2 gene is differentially regulated at the pretranslational level by intrinsic tissue-specific, as well as extrinsic pituitary and gonadal factors. The selected responses to reproductive hormonal status suggest that porf-2 may play a role in hypothalamic pituitary-gonadal interactions.