RESUMO
Histochemical reactions for NADPH-diaphorase (NADPH-d) were used to study the dynamics of NO synthesis activity in the cervical nuclei of the rat brain after i.v. administration of morphine hydrochloride. In normal conditions, NADPH-d activity was found in neurons in all the cervical nuclei. Acute and chronic administration of morphine at different doses (0.5 and 5 mg/kg) suppressed the NO-ergic activity of most cervical neurons. Decreases in the level of NADPH-d activity were different in different nuclei. NO-ergic changes were due to activation of opiate receptors, as they were dependent on the dose of morphine used, and treatment with the opiate antagonist naloxone restored the NO-ergic function of cervical neurons. Formation of tolerance to the analgesic effect of opiates was accompanied by significant but short-lived increases in NO synthesis activity. It is suggested that changes in the NO-ergic functions of cervical neurons may affect the balance of serotonin in the brain during opiate treatment.
Assuntos
Analgésicos Opioides/farmacologia , NADPH Desidrogenase/metabolismo , Neurônios/enzimologia , Óxido Nítrico Sintase/efeitos dos fármacos , Células do Corno Posterior/enzimologia , Núcleos da Rafe/enzimologia , Animais , Vértebras Cervicais , Masculino , Morfina/farmacologia , NADPH Desidrogenase/efeitos dos fármacos , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase/metabolismo , Células do Corno Posterior/metabolismo , Núcleos da Rafe/citologia , Ratos , Ratos WistarRESUMO
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.
Assuntos
Morfina/farmacologia , Neurônios/efeitos dos fármacos , Óxido Nítrico/metabolismo , Núcleos da Rafe/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Masculino , Morfina/administração & dosagem , NADPH Desidrogenase , Neurônios/metabolismo , Núcleos da Rafe/citologia , Núcleos da Rafe/metabolismo , Ratos , Ratos WistarRESUMO
Systemic administration of diacetylmorphine considerably reduced the number of NADPH diaphorase-positive (NO-synthesizing) neurons in rat brain raphe nuclei. This effect was blocked by naloxone. In animals with the withdrawal syndrome NO-ergic activity in raphe neurons increased and surpassed the normal.