Navegando por Palavras-chave "naloxone"

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    Involvement of the opioid system in the development and expression of sensitization to the locomotor-activating effect of ethanol
    (Cambridge Univ Press, 2000-12-01) Camarini, Rosana [UNIFESP]; Pires, Maria Laura Nogueira [UNIFESP]; Calil, Helena Maria [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Univ Calif San Francisco; Oregon Hlth Sci Univ
    Previous studies have shown that pretreatment with naloxone (Nlx), an opiate antagonist, attenuates the stimulating effect of ethanol. the purpose of the present study was to determine the influence of Nix on the development and expression of the sensitization to ethanol. Initially, effects of different doses of Nix on the response to a low dose of ethanol (2.0 g/kg) were assessed. Nix (1.0 and 3.0 mg/kg i.p.) decreased the stimulating effect of ethanol. Groups of mice were treated with saline or Nix (1.0 mg/kg i.p.) plus saline or ethanol (2.0 g/kg if) during 21 d. On day 25 of treatment all animals received an ethanol challenge (2.0 g/kg i.p.). It significantly increased the locomotor activity of mice that had received chronic ethanol (2.0 g/kg) once daily as compared to those that had received saline. Chronic administration of Nlx (1.0 mg/kg i.p.), during the same period of time, did not change the locomotor activity of the mice. However, the group concomitantly treated with Nix + ethanol did not develop sensitization to the locomotor-activating effect of ethanol. Another experiment was carried out to determine the effects of Nix on the expression of sensitization to ethanol. Acute pretreatment with Nix did not change the response of the mice that had developed sensitization to ethanol. These data show Nix's prevention of the development of ethanol-induced sensitization but not of its expression, suggesting an important role of the opioid neurotransmitter systems modulating the development of sensitization to the locomotor-activating effect of ethanol.
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    Morphine attenuates the expression of sensitization to ethanol, but opioid antagonists do not
    (Elsevier B.V., 2008-10-28) Abrahao, Karina Possa [UNIFESP]; Quadros, I. M.; Souza-Formigoni, M. L. O. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Tufts Univ
    Behavioral sensitization to ethanol is characterized by an increased locomotor activity after repeated exposure. A great variability exists among species and strains in the development of sensitization. There is a growing amount of evidence to indicate that the opioid system is involved in alcoholism; it is possible, therefore, that this system also modulates the sensitization to ethanol. in this study we evaluated the role of the opioid system in determining the variability of the sensitized response to ethanol. Mice received repeated administrations of ethanol (2.2 g/kg) or saline every other day for 10 days. According to their locomotor response on the last day of treatment, ethanol-treated animals were classified into two groups: sensitized or non-sensitized mice. After the treatment, mice were submitted to four challenges 48 h apart. in experiments 1 and 2, mice were challenged, respectively, with i.p. administration of opioid antagonists (naloxone or naltrexone) or an opioid agonist (morphine), followed immediately by 2.2 g/kg ethanol. in experiment 3, animals received morphine by i.c.v., followed by 2.2 g/kg of ethanol (i.p.). Pretreatment with opioid antagonists (naloxone or naltrexone) did not block the expression of ethanol sensitization; however pretreatment with morphine attenuated the increased locomotor activity after ethanol administration in sensitized mice. in experiment 4, after the ethanol or saline treatment, mice brains were processed and brain mu opioid binding was assessed by autoradiography using [3H]D-Ala2,N-mePhe4, Gly-ol5-enkephalin ([3H]DAMGO). No differences were seen between any of the groups of mice, so the agonist effect is not likely to be mediated by differences in binding to mu opioid receptors. (C) 2008 IBRO. Published by Elsevier B.V. All rights reserved.
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    Pro-epileptic effect of alfentanil in rats subjected to pilocarpine-induced chronic epilepsy
    (Elsevier B.V., 2006-05-15) Garrido Sanabria, Emilio Rafael; D'Andrea Vieira, Isabella; Fernanda Da Silveira Pereira, Maria; Coutinho Faria, Leonardo; Da Silva, Andre Cesar; Abrao Cavalheiro, Esper; Silva Fernandes, Maria Jose da; Universidade Federal de São Paulo (UNIFESP); Univ Brownsville
    Pharmacological induction of epileptiform activity is a complementary method to study the epileptogenic area in drug-resistant epileptic patients. Among the different activation methods, fentanyl derivatives (e.g. alfentanil) provide one of the most efficient tools in triggering epileptiform abnormalities in surgical candidates. in this study, we tested the pro-epileptic effect of different concentrations of alfentanil in hippocampal slices obtained from control and pilocarpine-treated chronic epileptic rats. the pro-convulsant action of alfentanil was also studied in control and pilocarpine-treated epileptic rats implanted with subdural and hippocampal electrodes for electroencephalographic recordings. in 90% of slices from control animals, application of affentanil (0.1-5 mu M) induced a significant enhancement in amplitude and number of population spikes recorded in the hippocampal CA1 region. in contrast, alfentanil produced a significant reduction in the amplitude of population spikes in slices from pilocarpine-treated epileptic rats. These changes were accompanied by a significant increase in the number of population spikes in the form of epileptiform multispike responses of epileptic slices. Naloxone (20 mu M) antagonized the effect of alfentanil in both control and epileptic slices, reducing the number of population spikes in slices from epileptic rats. in control rats, alfentanil induced epileptiform abnormalities in the hippocampal and cortical electroencephalographic recordings but only at concentrations higher than 200 [mu g/kg (e.g. 350 mu g/kg). Lower doses of affentanil (25 mu g/kg) elicited epileptiform abnormalities only in chronic epileptic rats. the potent action of a minimal dose of alfentanil in inducing epileptiform activity suggests an enhancement of the pro-convulsant action of mu-receptor opioids in chronic temporal lobe epilepsy. (c) 2006 Elsevier Inc. All rights reserved.