title: Developmental changes in opiate-induced analgesia in deer mice: sex and population differences.
abstract: We examined developmental changes in nociception and mu (morphine) and kappa (U-50,488) opiate-induced analgesia in male and female deer mice of two different populations; Peromyscus maniculatus artemisiae from a mainland region and P. m. angustus from a small island. Both populations displayed significant developmental changes in nociception and morphine (10 mg/kg) and U-50,488 (10 mg/kg)-induced analgesia. Basal thermal response latencies (nociceptive responses) and the levels of mu and kappa opiate-induced analgesia increased over 14-35 days of age, with maximum analgesic responses in adults (35+ days of age). In both of the populations, young (neonatal-weaning) male mice displayed significantly higher thermal response latencies and greater levels of naloxone (1.0 mg/kg) antagonized opiate-induced analgesia than young females. There were also population differences in the levels of analgesia, the insular mice displaying greater mu and lower kappa opiate-induced analgesic responses than the mainland animals. The population differences in mu and kappa opiate-induced analgesia were evident in young and adult mice of both sexes. These results show that there are significant sex and population differences in nociception and opiate-induced analgesia in young (neonatal-weaning) and adult deer mice.
authors.affiliation: Division of Oral Biology, Faculty of Dentistry, University of Western Ontario, London, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Kavaliers
authors.forename: D G
authors.initials: DG
authors.lastname: Innes
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D000375:Aging / Q000502:physiology*; D000698:Analgesia; D000818:Animals; D005260:Female; D006358:Hot Temperature; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010542:Peromyscus / Q000254:growth & development* / Q000502:physiology; D011759:Pyrrolidines / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D012727:Sex Characteristics; D013045:Species Specificity
chemical_list: D011759:Pyrrolidines; D011957:Receptors, Opioid; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine