Cortical and pontine variations occurring in the voltammetric no signal throughout the sleep-wake cycle in the rat

Voltammetric measurements of nitric oxide (NO) were performed either in the frontal cortex (Cx) or in the nucleus raphe dorsalis (nRD) of rats equipped for polygraphic recordings. In the frontal cortex, the 650 mV signal related to NO exhibited its highest height during the waking state (W) and decreased slightly during slow-wave sleep (SWS) and even more during paradoxical sleep (PS). In the nRD, opposite variations were observed, i.e. the signal tended towards an increase during SWS and raised more consistently during PS versus W. Recordings performed either in the Cx or the nRD, throughout the light (12-h) and dark (12-h) periods, exhibited opposite nycthemeral changes, i.e. the signal height was higher in the Cx and lower in the nRD during the dark period and conversely for the light one. Paracrine and synaptic mechanisms taking place within the pons and, at least partly, also reflected in the Cx need to be further investigated.