title: The role of opioids in the analgesic response of rats during the estrous cycle.
abstract: The analgesic response was evaluated by the tail immersion test in female rats during each phase of the estrous cycle. The reaction time (mean +/- SEM) for tail withdrawal from the hot water bath was faster during proestrus (5.78 +/- 0.28 s) and decreased significantly during estrus (5.31 +/- 0.30 s) and diestrus 1 (5.40 +/- 0.21 s). Blockade of opiate receptors with naloxone (2 mg/kg, ip) increased the sensitivity to the noxious stimulus only during proestrus (6.46 +/- 0.42 vs 5.02 +/- 0.41 s). These results suggest that the effects of gonadal steroids on nociception may involve an opioid pathway.
authors.affiliation: Departamento de Ciências Fisiológicas, Faculdade de Odontologia, Universidade Estadual Paulista, Araçatuba, Brasil.
authors.forename: N
authors.initials: N
authors.lastname: Molina
authors.forename: M T
authors.initials: MT
authors.lastname: Bedran-de-Castro
authors.forename: J C
authors.initials: JC
authors.lastname: Bedran-de-Castro
mesh_terms: D000698:Analgesia; D000818:Animals; D004971:Estrus / Q000502:physiology*; D005260:Female; D009270:Naloxone; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time; D011957:Receptors, Opioid / Q000187:drug effects; D013623:Tail
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone