Immunohistochemical Study on the Distribution of LHRH-Like Substance in the Vertebrate Brain

Abstract

Distribution of immunoreactive LHRH-like substance was studied in the brains of 5 species of mammals, 1 species of birds, 7 species of reptiles, 7 species of amphibians, 6 species of teleosts, 1 species of elasmobranchs, and 2 species of cyclostomes. For this pur-pose, two different anti-synthetic LHRH sera (AsI : anti-Tyr5-BSA-LHRH serum; AsII : anti-Gly10-BSA-LHRH serum) were used.Among mammals and birds, LHRH-positive perikarya were observed by both AsI and AsII in the septo-preoptic region of the cat, and by AsI in several regions of the fore-brain including the septo-preoptic region of the guinea pig. However, they were not detected in the brains of the rat, mouse, hamster and Japanese quail in either case of AsI or AsII. In any case mentioned above, LHRH-positive material was found in the nerve terminals of the median eminence.In reptiles and amphibians, similar results were obtained by both AsI and AsII. LHRH-positive perikarya were generally distributed in the septo-preoptic region, and their nerve terminals were consistently detected in the median eminence. Only in Xenopus, however, LHRH-positive perikarya were distributed in the peri-chiasmatic region, the infundibular region, the anterior part of the optic tectum and the olfactory bulb, in addition to the septo-preoptic region. In most species of reptiles and amphibians, intra- and extra-hypothalamic LHRH-pathways, which proceed toward (1) the median eminence, (2) the olfactory bulb, (3) the optic lobe, and (4) the lower brain stem were demonstrated.LHRH-positive material was detected by both AsI and AsII in the neurohypophyses of the eel, goldfish and puffer, but only by AsI in the lamprey. Among the former three species, only in the eel, LHRH-positive perikarya were observed : they were distributed in the ventro-medial part of the telencephalon and the olfactory bulb, and they projected their fibers mainly to the anterior portion of the neurohypophysis. In the lamprey, those perikarya were distributed only in the preoptic nucleus. LHRH-positive material was detected by both AsI and AsII in the brain of the dogfish. However, distribution of those fibers were quite different from other species mentioned above, and no LHRH-positive terminals were detected in the median eminence. In the brain of the rainbow trout, loach, medaka and hagfish, LHRH substance was not detected by either AsI or AsII.