C-type natriuretic peptide (CNP), the most abundant natriuretic peptide hormone in the brain, plays an important role in neuroendocrine function. The physiological effects of CNP are mediated by the natriuretic peptide receptor-B (NPR-B). Although CNP and NPR-B have been detected in several brain regions, little is known about the neuroanatomical localization of NPR-B protein in the brainstem. In the present study, we investigated the topographical distribution of NPR-B immunoreactivity in the monkey brainstem. The data demonstrate widespread NPR-B immunoreactivity throughout the brainstem. NPR-B immunoreactivity was located in the superior colliculus, inferior colliculus, periaqueductal gray, oculomotor nucleus, red nucleus, ventral tegmental area, substantia nigra, and cerebral peduncle of the midbrain, as well as in the abducens nucleus, medial vestibular nucleus, lateral vestibular nucleus, parabrachial nucleus, locus coeruleus, trigeminal motor nucleus, pontine reticular nucleus, facial nucleus, oral part of the spinal trigeminal nucleus, cochlear nucleus, raphe magnus nucleus, raphe pallidus nucleus, pontine nucleus of the pons, the dorsal motor nucleus of the vagus, hypoglossal nucleus, nucleus tractus solitarius, gracile nucleus, cuneate nucleus, medial vestibular nucleus, spinal trigeminal nucleus, nucleus ambiguus, lateral paragigantocellular nucleus, lateral reticular nucleus, and the inferior olivary nucleus of the medulla oblongata. The widespread distribution of NPR-B-immunoreactive structures throughout the monkey brainstem indicates that CNP may be involved in several physiological mechanisms, acting as a neurotransmitter and/or neuromodulator.
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