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kappa-opioid receptor-mediated analgesia: hotplate temperature and sex differences
F van Haaren1, S Scott, L B Tucker
1Department of Psychology, University of Florida, Gainesville, FL 32611-2250, USA. haaren@psych.ufl.edu
Abstract:
The present experiment was designed to investigate the dose-effect and time-effect functions of the kappa-opioid receptor agonist [5alpha,7alpha, 8beta)-(-)-N-Methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro(4, 5)dec-8-yl]benzeneacetamide] (U69,593) in intact and gonadectomized male and female rats as a function of hotplate temperature (45 degrees C or 51 degrees C). At 45 degrees C baseline lick latencies were longer in female rats than in male rats. Lick latencies increased dose-dependently in all subjects except intact female rats. U69,593 increased lick latencies as a function of time since its administration in all subjects. At 51 degrees C baseline lick latencies did not differ between groups and they increased dose-dependently in all subjects. The effectiveness of U69,593 decreased as a function of time since its administration, but not in castrated male rats. These observations suggest that gonadal hormones could play a role in modulating the behavioral effects of U69,593 when subjects are tested at different hotplate temperatures.
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