MNAR/PELP1 is a recently identified scaffold protein in the human that modulates the non-genomic activity of estrogen receptors by facilitating linkage/crosstalk with the Src/Erk activation cascade. We report herein the cloning of rat MNAR/PELP1 and provide new information concerning its distribution in the rat female brain and its degree of co-localization with estrogen receptor- (ER-) and GnRH. PCR-based cloning of MNAR/PELP1 from rat hypothalamus yielded a transcript of 3.4KB, which shows 86% homology to the published human MNAR/PELP1 sequence and retained all the key binding motifs (PXXP, LXXLL and glutamic acid clusters) in its primary structure that are known to be critical for its interaction with Src and steroid receptors. RT-PCR revealed that the MNAR/PELP1 transcript is expressed in many regions of the brain, and immunohistochemistry studies showed intense MNAR/PELP1 immunoreactivity (MNAR/PELP1-ir) in areas such as the hypothalamus, cerebral cortex, hippocampus, amygdala, and cerebellum. MNAR/PELP1-ir principally localized in the nucleus, but some cytoplasmic and plasma membrane-associated staining was also observed. MNAR/PELP1-ir was also primarily neuronal, although some localization in glia cells was observed in select brain regions. Co-localization studies revealed that a majority of ER- positive cells in the brain co-localized MNAR/PELP1-ir. In contrast, MNAR/PELP1-ir rarely co-localized in GnRH neurons. In conclusion, the current study provides evidence that MNAR/PELP1 is expressed in key neural tissues of the rat brain that are known targets of steroid action, that its expression is primarily neuronal, and that MNAR/PELP1-ir is strongly co-localized in ER-, but not GnRH neurons in the rodent brain.