Anatomical And Functional Studies On The Subependymal OT-L1 Neuronal Plexus In The Rat

The posterior pituitory secretes two important peptide hormones, arginine vasopressin(AVP) and oxytocin(OT). AVP and OT are involved in many functions of the central and peripheral nervous system.They mainly serve to maintain arteriolar perfusion pressure and plasma osmolality. The hormone release involves a stimulus-secretion-coupled exocytotic process that is triggered by the arrival of action potential generated at the cell soma located in the PVN, SON and accessory magnocellular nuclei. Both the frequency and the patterning of these action potentials are important determinants of the amount of the hormone released. In general the two important factors governing neurohypophysial secretion are magnocellular intrinsic membrane properties and synaptic inputs. The synaptic inputs, to which much attention have been paid, are mainly from the brain stem and forebrain structures including the diagonal band of Broca(DBB) and cells located near the lamina terminalis.Recently it has been demonstrated that there is a band of neurons, primary OT-LI directly bordering on the third ventricle. Retrograde tracing in combination with immunohistochemical technique has proved that many of them project to the posterior pituitary. Such a subependymal plexus(SEP) has a total of 650 cells, about 77% of cells in the pmPVN. Taken its location into consideration, it is reasonable to...