The hypothalamo-hypophyseal neurosecretory system in some fishes
Sahai, S.
Folia Morphologica 29(4): 339-343
1981
ISSN/ISBN: 0015-5640 PMID: 7319408 Document Number: 179621
The hypothalamo-hypophyseal neurosecretory system was studied in Ambassis ranga, Puntius ticto and Rohtee cotio. The preoptic nucleus [NPO] is well developed in all 3 fish and the nucleus lateralis tuberis is absent. The neurosecretory material in the NPO is granular in Ambassis and Rohtee but in Puntius large neurosecretory droplets are present and they show a definite sequence in their formation. The axons of the preoptico-hypophyseal tract are more distinct in Puntius and have a beaded appearance. The intensity of neurosecretory material varies from the NPO to the neurohypophysis. It is greatest in the region of the tract where it enters the neurohypophysis, perhaps because of the accumulation of neurosecretory material in that part. Prominent Herring bodies are found which are swollen parts of the axons with accumulated neurosecretory material. This suggests their role in providing a larger surface area for the release of biologically active principles into the blood. The neurohypophysis interdigitates profusely with the adenohypophysis. Its smaller branches extend into the pars distalis rostrale and proximale while the main trunk arborizes in the pars intermedia. In all 3 fish the neurohypophysis is richly vascularized. The terminals of the neurosecretory fibers in the region of the pars intermedia are frequently seen resting on the surface of blood vessels.