Abstract
By using the Golgi impregnation methcd in the study of lamprey hypothalamus, it is demonstrated that the nucleus preopticus consists mainly of neurosecretory neurons similar to the type of CSF-contacting neurons.A small number of horizontal cells are also detected in this area.In addition to these cells another type of CSF-contacting neurons are seen in the ventral part of the nucleus preopticus.While both nucleus hypothalami dorsalis and nucleus hypothalami ventralis situated in the posterior part of the hypothalamus are occupied exclusively by the CSF-contacting neurons bearing the ventricular process, the nucleus recessus posterioris hypothalami in this area are found to have the neurons equipped with processes bearing varicosities that are projected toward the ventricular surface.Ten to 12 hours after the administration of HRP that is retrogradly transported in axon from the hypophysis, this agent appeared in several sites, such as the CSF-con-tacting neurons of the nucleus hypothalami ventralis and nucleus hypothalami dorsalis, both just above the pars nervosa, as well as neurosecretory neurons of the nucleus pre-opticus.These results may intimate that the pars nervosa of the lamprey hypophysis is innervated from the monoaminergic CSF-contacting neurons located in the lateral wall of the third ventricle, in addition to the neurosecretory nerve fibers.
