DISTRIBUTION OF GASTRIN-RELEASING PEPTIDE BOMBESIN-LIKE IMMUNOREACTIVITY IN THE RAINBOW-TROUT BRAIN

The distribution of gastrin-releasing peptide(14-27)/bombesin- like im munoreactivity was studied in the brain of the teleost Oncorhynchus my kiss using an indirect immunoperoxidase technique. Cell bodies were on ly found in the hypothalamic nuclei posterioris periventricularis, the anterior part of the recessus lateralis, and in the recessus posterio ris. Immunoreactive fibers were widely distributed in the diencephalon , midbrain, and hindbrain. The highest density of immunoreactive fiber s was found in the hypothalamus, whereas a moderate to low density of fibers was visualized in the periventricular thalamus. In the midbrain , a moderate density of fibers was observed at the level of the nuclei lateralis and centralis of the torus semicircularis, the stratum albu m centrale of the optic tectum, the nucleus of the rostral mesencephal ic tegmentum, the nuclei lateralis valvulae, the lemnisci lateralis, i stmi and locus coeruleus, as well as in the hindbrain at the level of the nuclei gustatorius secundarius, cerebelli, descendens nervi trigem ini, and funiculi lateralis. These data suggest that the peptide could be involved in neuroendocrine (LT, nRL, nRP), visual (OT, nRTM, TS, I s), auditory (TS), and nociceptive (Vd, nufl) mechanisms.