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[NO-ergic rat brain commissural neurons in the norm and during opiate administration]
I V Diuĭzen1, I I Deridovich, R A Kurbatskiĭ
1Department of Histology, and Faculty of Postgraduate Training Department of Narcology, Vladivostok State Medical University, Laboratory of Pharmacology, Institute of Marine Biology, RAS Far Eastern Branch, Vladivostok.
Abstract:
Using histochemical reaction demonstrating NADPH-diaphorase (NADPH-d), the dynamics of NO synthesis was studied in the rat brain raphe nuclei following intravenous injection of morphine hydrochloride. In normal conditions NADPH-d activity was demonstrated in neurons of all raphe nuclei. Acute and chronic administration of morphine in different doses (0.5 mg/kg and 5 mg/kg) was found to inhibit NO-ergic activity of the major part of raphe nuclei neurons. The depression of NADPH-d activity was unequal in different nuclei. The NO-ergic changes are caused by an activation of opiate receptors, as they depend on morphine dose, while the application of opiate antagonist naloxone restores the NO-ergic function of raphe neurons. Formation of tolerance to opiate analgetic effect is accompanied by a significant, though short-lasting increase of NO synthesis activity. It is suggested that the changes in NO-ergic function of raphe neurons may influence brain serotonin balance after opiate administration.