Stimulates smooth muscle contraction (PubMed:6882442). Induces sighing by acting directly on the pre-Botzinger complex, a cluster of several thousand neurons in the ventrolateral medulla responsible for inspiration during respiratory activity (By similarity). Contributes to the induction of sneezing following exposure to chemical irritants or allergens which causes release of NMB by nasal sensory neurons and activation of NMBR-expressing neurons in the sneeze-evoking region of the brainstem (By similarity). These in turn activate neurons of the caudal ventral respiratory group, giving rise to the sneezing response (By similarity). Contributes to induction of acute itch, possibly through activation of the NMBR receptor on dorsal root ganglion neurons (By similarity). Increases expression of NMBR and steroidogenic mediators STAR, CYP11A1 and HSD3B1 in Leydig cells, induces secretion of testosterone by Leydig cells and also promotes Leydig cell proliferation (PubMed:29632025). Plays a role in the innate immune response to influenza A virus infection by enhancing interferon alpha expression and reducing expression of IL6 (By similarity). Plays a role in CSF1-induced proliferation of osteoclast precursors by contributing to positive regulation of the expression of the CSF1 receptor CSF1R (By similarity). In neurons of the retrotrapezoid nucleus//parafacial respiratory group, expressed on neuron projections which project into the pre-Botzinger complex. Higher expression in the central nervous system (CNS) than in peripheral tissues. Highest levels are found in the olfactory bulb. Relatively high levels in the CNS (including the cerebral cortex, cerebellum, spinal cord, medulla oblongata, midbrain, hypothalamus, hippocampus, and hypophysis) and in peripheral tissues such as the pancreas, adrenal gland, testis, ovary and cecum. Moderate levels are found in the rectum, heart and pons with low expression levels detected in the bone marrow and duodenum. Other tissues show no or low levels of expression. During the sow estrus cycle, highest levels are found in the hypothalamus during proestrus, decrease during estrus and metestrus and increase again during diestrus. In the pituitary gland, levels decrease from proestrus to estrus, increase at metestrus and decrease again at diestrus. In the ovary, expression peaks at proestrus, decreases slightly at estrus, decreases significantly at metestrus and increases at diestrus. During boar postnatal development, expression peaks in the hypothalamus at day 60 and decreases thereafter. In the pituitary gland, expression peaks at day 30 and decreases thereafter. In the testis, expression peaks at day 3 with lowest levels at day 60 and expression then gradually increases from day 60 to day 120. Belongs to the bombesin/neuromedin-B/ranatensin family.