It is generally accepted that the voltage-gated, tetrodotoxin-sensitive sodium channel, NaV1.7, is selectively expressed in peripheral ganglia. However, global deletion in mice of NaV1.7 leads to death shortly after birth (Nassar et al.  Proc. Natl. Acad. Sci. U. S. A. 101:12706–12711), suggesting that this ion channel might be more widely expressed. To understand better the potential physiological function of this ion channel, we examined NaV1.7 expression in the rat by in situ hybridization and immunohistochemistry. As expected, highest mRNA expression levels are found in peripheral ganglia, and the protein is expressed within these ganglion cells and on the projections of these neurons in the central nervous system. Importantly, we found that NaV1.7 is present in discrete rat brain regions, and the unique distribution pattern implies a central involvement in endocrine and autonomic systems as well as analgesia. In addition, NaV1.7 expression was detected in the pituitary and adrenal glands. These results indicate that NaV1.7 is not only involved in the processing of sensory information but also participates in the regulation of autonomic and endocrine systems; more specifically, it could be implicated in such vital functions as fluid homeostasis and cardiovascular control. J. Comp. Neurol. 504:680–689, 2007. © 2007 Wiley-Liss, Inc.