title: Predator-induced opioid and non-opioid mediated analgesia in young meadow voles: sex differences and developmental changes.
abstract: The present study examined developmental changes in the nociceptive responses of male and female meadow voles, Microtus pennsylvanicus, exposed to a garter snake, a natural predator of young voles. After 15 min of exposure to the presence of a garter snake, neonatal-juvenile voles (5-20 days of age) displayed naloxone (1.0 mg/kg)-sensitive opioid mediated analgesic responses, while after a brief 30-s exposure to the snake, voles displayed a higher amplitude, non-opioid analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A) agonist, 8-hydroxy-2-(di-n-propylamino)tetralin. The levels of opioid and non-opioid mediated analgesia declined during development as the threat presented by the snake decreased. Young female voles also displayed a significantly greater non-opioid, 5-HT1A sensitive analgesia than males, with no significant sex differences in the lower amplitude opioid analgesia. These results indicate that young (neonatal) meadow voles that are exposed to a naturally threatening stimulus display sexually dimorphic analgesic responses. These findings also illustrate the need to consider the ecological context when examining environmentally-induced analgesia.
authors.affiliation: Department of Psychology, University of British Columbia, Vancouver, Canada.
authors.forename: L M
authors.initials: LM
authors.lastname: Saksida
authors.forename: L A
authors.initials: LA
authors.lastname: Galea
authors.forename: M
authors.initials: M
authors.lastname: Kavaliers
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000698:Analgesia; D000818:Animals; D003411:Arvicolinae / Q000502:physiology / Q000523:psychology*; D001362:Avoidance Learning / Q000502:physiology*; D004723:Endorphins / Q000502:physiology*; D005260:Female; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D011235:Predatory Behavior; D012727:Sex Characteristics
chemical_list: D004723:Endorphins; D009270:Naloxone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin