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Naloxone and chlordiazepoxide: effects on acquisition of DRL and signalled DRLDepartment of Psychology and Centre for Neuroscience, University of Otago, Dunedin, New Zealand
Department of Psychology and Centre for Neuroscience, University of Otago, Dunedin, New Zealand The ability of the opiate antagonist, naloxone, to block the anti-conflict effects of the benzodiazepines suggests endogenous opioid involvement in the mechanism of action of these drugs. However naloxone's ability to attenuate the effects of the benzodiazepines in animal conflict paradigms appears to be schedule specific. It is effective in acquisition of a differential reinforcement of low rates of response (DRL) schedule but not in acquisition of a non-reward successive discrimination schedule. We tested the effects of naloxone and chlordiazepoxide on acquisition of DRL and on acquisition of a version of the same schedule (signalled DRL) which was like successive discrimination in having an explicit visual signal of non-reward. Chlordiazepoxide (5 mg/kg i.p.) impaired DRL responding by increasing burst responding and premature responding close to the criterion interval. Naloxone (3 mg/kg i.p.) alone decreased burst and premature responding, it also blocked the effects of chlordiazepoxide. The signalled DRL schedule produced essentially similar drug effects. Clearly the critical schedule parameter determining whether naloxone will attenuate the anxiolytic actions of the benzodiazepines is not the presence or absence of an explicit signal of conflict.
Key Words: naloxone • chlordiazepoxide • DRL • signalled DRL • non-reward
Journal of Psychopharmacology, Vol. 6, No. 1,
88-94 (1992) |
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