CORTICAL AND PONTINE VARIATIONS OCCURRING IN THE VOLTAMMETRIC NO SIGNAL THROUGHOUT THE SLEEP-WAKE CYCLE IN THE RAT

摘要

Studies related to the endothelium-derived relaxing factor (10) initiated researches that led to the discovery of a biological paracrine messenger identified as nitric oxide (NO) (15). It is now also currently reported that the synthesis of this gaseous messenger is achieved, from L-arginine, by NO-synthases (NOS: neuronal, endothe-lial and inducible isoforms) and that it lasts in an equimolar production of NO and L-citrulline (2, 17, 27). To date, the implication of NO has been documented for three main functional aspects, i.e. anti-microbial and anti-tumoral activities in immune responses, vasodilatation and neurotransmission (2, 26, 29). Regarding neu-rotransmission, it appears that NOS is colocalised in the brain systems involved in the sleep-wake states genesis and/or regulation (11, 20, 21), at least, with neuro-transmitters like serotonin, acetylcholine or somatostatin (1, 23, 28). Moreover, on the basis of pharmacological approaches, it is now also reported that NO contained in neurons of the pontine tegmentum facilitates mainly PS (3, 4, 9,14). This is particularly true for the nucleus raphe dorsalis (nRD) where local injections of either NOS inhibitors or NO donors inhibit or facilitate PS respectively (7).