Cellular orientation of atrial natriuretic peptide in the human brain

Many peptide hormones and neurotransmitters have been detected in human neuronal tissue. The localisation of atrial natriuretic peptide (ANP) in the human brain was considered to be both interesting and relevant to the understanding of neurochemistry and brain water–electrolyte homeostasis. This vasoactive peptide hormone has been localised in rat and frog neuronal tissue. In the present study, we report the immunohistochemical localisation of ANP in autopsy samples of human brain tissue employing the avidin–biotin–peroxidase complex technique, using an antibody against a 28 amino acid fragment of human ANP. The most intense staining of immunoreactive ANP was detected in the neurones of preoptic, supraoptic and paraventricular nuclei of the hypothalamus, epithelial cells of the choroid plexus and ventricular ependymal lining cells. Immunoreactive neurones were also observed in the median eminence, lamina terminalis, infundibular and ventromedial nuclei of the hypothalamus, and in neurones of the brain stem, thalamic neurones and some neurones of the caudate nucleus. The network of ANP cells in numerous hypothalamic centres may regulate the salt and water balance in the body through a hypothalamic neuro-endocrine control system. ANP in the brain may also modulate cerebral fluid homeostasis by autocrine and paracrine mechanisms.