Progesterone and norethisterone have different effects on tachykinin-like immunoreactivity in rat cortex and striatum

Objective: The purpose of this study was to investigate the effects of prog esterone and the most commonly prescribed synthetic progestogen. norethiste rone, on regional immune-like reactivity of neuropeptide Y (NPY), substance P (SP), neurokinin A (NKA) and neurotensin (NT) in brains of female ovarie ctomized estradiol-substituted rats. Results: Norethisterone + estradiol-tr eated rats had 44% lower SP levels compared with estradiol-only-treated in frontal cortex and 20% lower NKA levels in comparison with progesterone + e stradiol-treated in frontal cortex. Progesterone + estradiol-treated rats h ad 66% lower SP levels in striatum in comparison with both estradiol-only-t reated and norethisterone + estradiol-treated. No significant results were found for NPY and NT. Conclusion: Progesterone and the synthetic progestoge n, norethisterone, have different effects on SP- and NKA-like immunoreactiv ity in rat cortex and striatum. The effects of NET on SP- and NKA-like immunoreactivity in frontal cortex m ay contribute to the mood effects ascribed to this progestogen in clinical usage. (C) 2001 Elsevier Science B.V. All rights reserved.