Implicated in the regulation of circadian rhythms through autocrine and/or paracrine actions. Stimulates the contraction of rectum and elevation of blood pressure. Expressed in the CNS, spleen and testis. Specifically expressed in the suprachiasmatic nuclei (SCN) of the hypothalamus. Expression has a diurnal peak under light/dark cycling, but remains stable under constant darkness. Belongs to the NmU family.