Immunohistochemical Localization of Delta Sleep-Inducing Peptide (DSIP) in the Brain and Pituitary of the Cartilaginous Fish Scyliorhinus canicula
Résumé
VALLARINO, M., M. FEUILLOLEY, L. YON, Y. CHARNAY AND H. VAUDRY. Immunohistochemical localization of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula. PEPTIDES 13(4) 645-652, 1992.-The distribution of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula was investigated using the indirect immunofluorescence technique. Delta sleep-inducing peptide-like immunoreactive cell bodies were mainly observed in the nucleus lateralis tuberis of the hypothalamus. Immunolabeled perikarya were also distributed in the nucleus lobi lateralis hypothalami and in the dorso-lateral wall of the recessus posterioris. Most of these cells, located in the subependymal layers of the infundibulum and lateral lobes, had the typical aspect of cerebrospinal fluid-contacting elements. The DSIP-like immunoreactive fibers were localized in the basal telencephalon, within the regions of the nucleus interstitialis commissurae anterioris and the nucleus entopeduncularis. A dense network of DSIP-positive fibers was seen throughout the mid-caudal hypothalamus, the lateral lobes, and the posterior lobe. In the pituitary, numerous DSIP-like immunoreactive cells were detected in the median lobe of the pars distalis. In particular, a high concentration of cells was seen in the dorsal wall of the median lobe, an area which is known to contain melanin-concentrating hormone (MCH)-producing cells. Comparison of the distribution of DSIP-and MCH-like immunoreactive cells revealed that the two neuropeptides are stored in the same cells of the median lobe of the pituitary. These findings provide the first evidence for the presence of a DSIP-related peptide in fish. The distribution of the immunoreactive material supports the view that DSIP may act as a neuromodulator and/or a hypophysiotropic factor. Moreover, the presence of DSIP-like immunoreactive cells in the pars distalis suggests that this peptide may exert autocrine or paracrine effect in the pituitary. Delta sleep-inducing pepfide Brain Pituitary Immunohistochemistry Dogfish Scyliorhinus canicula DELTA sleep-inducing peptide (DSIP) is a nonapeptide that was originally isolated from the cerebral blood of rabbit for its hypnogenic activity (26). The amino acid sequence of DSIP is totally distinct from that of other neuropeptides identified so far. However, different molecular forms of DSIP, including large putative precursors (5,6), smaller forms (3), and phosphorylated (14) or glycosylated derivatives (5), have been identified, suggesting the existence of a family of DSIP-related peptides (17). Although the exact structure of the natural biologically active form of DSIP is still discussed, the occurrence of DSIP-like im-munoreactive peptides has been demonstrated in the central nervous system of mammals (7-10,23,34). Numerous DSIP-containing cells are distributed in the para-and periventricular hypothalamic nuclei (7), which are known as major cardiovas-cular regulatory areas (25). Also, DSIP-producing neurons are abundant in the ventrolateral septum and in the preoptic region of the hypothalamus (7-9,15). Consonant with the presence of DSIP in the hypothalamic area, it has been shown that besides its sleep-inducing activity, DSIP decreases blood pressure, regulates body temperature, and modulates the response to stress (I 7,18,36). Neuropeptides immunologically related to DSIP have been detected in various peripheral organs including the gut (4) and the adrenal medulla (6,12). The occurrence of DSIP-like peptides has also been demonstrated in the pituitary gland (1,2,5-' Requests for reprints should be addressed to M. Vallarino. 645