Vasoactive intestinal peptide receptors in rat spleen and brain: a shared communication network

The binding sites for [125I]-vasoactive intestinal polypeptide (125I-VIP) in rat spleen and brain were localized using autoradiography. High affinity VIP receptors are present in rat spleen, and competition studies reflect structure-activity relationship typical of VIP receptors elsewhere. In spleen, specific binding of 125I-VIP occurs on red pulp and, most abundantly, on the periarteriolar lymphoid sheath (PALS) of white pulp. Unlabeled VIP competes for binding to both red pulp and white pulp, whereas secretin displaces binding to PALS more potently than to red pulp. This indicates that expression of VIP and/or secretin type receptors is limited to T lymphocytes of white pulp. In red pulp, VIP receptor bearing cells probably are monocytes/macrophages since this is the most abundant red pulp cell type. In the brain, VIP receptors are widely distributed with the highest densities occurring in "sensory" areas. Receptors are abundant in the olfactory bulb, thalamic nuclei, several cranial nuclei and the area postrema. High levels of 125I-VIP binding occurred on inner walls of blood vessels of the brain and spleen. The distribution patterns of receptors for "VIP-ergic signals" in brain and lymphoid tissue indicate interrelatedness of the two organ systems. This may serve as one biochemical rationale for a bio-psycho-social view of health and disease.