Nitric oxide as a modulator of electrical activity in magnocellular neurons of the rat supraoptic nucleus

Abstract

The role played by Nitric Oxide (NO) as a neurotransmitter in controlling the electrical activity of Magnocellular Neurons of the SON (MNCs) was postulated after reports that hyperosmotic stimulation of these cells lead to an increase in the expression of nitric oxide synthase (NOS) mRNA and of oxytocin (OT) and vasopressin (VP) secretions. Several reports show that NO can act both indirectly and directly upon the MNCs. Indirectly, by potentiating inhibitory synaptic inputs, and directly by acting on specific ionic currents which lead to a decrease in the firing frequency of the MNCs. As a consequence of this latter effect, there is a decrease in the secretion of OT and VP. Moreover, channels from the TRPV (transient receptor potencial vaniloid) family seems to work as osmomechano receptors and also able to affect the electrical activity of the MNCs. In view of these findings this project aims at investigating the effects of NO upon these regulatory pathways of the MNCs, by using electrophysiological techniques (patch clamp) in slices and isolated cells of the SON, as well as current molecular biology techniques (RT-PCR) in order to identify the molecular characteristics (OT and/or VP) of the neurons under investigation. Intracellular ionic activities and signaling molecules will be detected with the use of specific fluorescent dyes and confocal microscopy, in order to gain insight on the biochemical regulatory pathways involved in the control of the MNCs activity. (AU)