The Distributions And Interrelations Of Nitric Oxide Synphase (NOS), Oxytocin (OT), And 8-arginine Vasopressin (AVP) Immunoreactive (IR) Neurons In The Maynocellullar Neurosecretory Nuclei Of The Rat Hypothalamus

Objective : In order to provide the anatomic date for the role of nitric oxide (NO) in modulating many physiological behaviors such as reproduction, sexual behaviors and the central visceral and cardiovascular functions,we investigated the distributions and interrelations of nitric oxide synphase (NOS),oxytocin (OT),and 8-arginine vasopressin(AW) immunoreactive (IR) neurons in the maynocellullar neurosecretory nuclei of the rat hypothalamus. This give the basis material for exploration of the neuroendocrine medianism of the hypothalamus.Methods : The morphologies, distributions and coexistence of NOS positive neuronal cell bodies, OT immunoreactive and AVP immunoreactive neuronal cell bodies were observed in the different nucleus of the hypothalamus by combination of OT and AW immunocytochemical methods and NADPH-diaphorase histochemistry.Results: 1. The morphology and distribution of NOS positive neurons and OT immunoreactive neurons were fundamental similarity in the PVN, and high degree of coexistence of NOS with OT was found also. The relative frequency of such coexistence varied between the different parts of the PVN, with the highest degree of NOS-OT coexistence in AC,PVN and PVL but a minor coexistence in PvPO was found.2.The morphology and AVP-IR neurons were fundamental similarity in the SON, and high degree of coexistence of NOS with OT or AW was found also.However, the location of NOS-OT neurons and NOS-AVP neurorng is different.Most NOS-OT neurons located in the dorsal part of SON and NOS-AVP cells in it's ventral aspect. 3.NOS-OT and NOS-AVP positive cerebrospinal fluid-contacting neurons could be found in the dorsal wall,ventral wall and bottom wall of Third ventricle(3V). The distribution and the ratios of neurons expressing both markers(NOS and AVP,NOS and OT)in each wall of 3V were different.4.Coexistence was also found in other accessory magnocellular nucleus of the rat hypothalamus.ConclusionrThe ratios of such coexistence varied between the different nuclei parts or different subdivisions of the hypothalamus which suggested that these different regions had different functions.NO may differenially modulate the activitives of OT and AVP neurons.