title: Tolerance and cross-tolerance with morphine in mice selectively bred for high and low stress-induced analgesia.
abstract: Mice selectively bred for high (HA) and low (LA) swim-induced analgesia were exposed to two different stress paradigms; one consisting of a 3-min swim at 20 degrees C daily for 14 days, and the other consisting of 3-min swims repeated at 2-h intervals for 48 h. Both forms of chronic stress resulted in the development of tolerance to swim-induced antinociception to a greater degree in the HA mice than in control (C) mice, but were both ineffective at inducing tolerance in LA mice. Swimming repeated at 2-h intervals for 48 h resulted in cross-tolerance with morphine in HA and C mice. Naloxone (1 and 10 mg/kg, IP) failed to antagonize swim-induced analgesia in mice that had experienced chronic swimming in the 2-h/48-h paradigm. The daily swimming paradigm failed to produce cross-tolerance with morphine analgesia in any line. Differential degree of tolerance in three lines supports a hypothesis that selective breeding for high and low stress-induced analgesia has modified the degree of opioid involvement in the endogenous analgesia mechanisms.
authors.affiliation: Department of Behavioral Physiology, Polish Academy of Sciences, Mrokow.
authors.forename: I
authors.initials: I
authors.lastname: Panocka
authors.forename: P
authors.initials: P
authors.lastname: Marek
authors.forename: B
authors.initials: B
authors.lastname: Sadowski
mesh_terms: D000818:Animals; D004361:Drug Tolerance; D005260:Female; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D011930:Reaction Time / Q000187:drug effects; D013045:Species Specificity; D013315:Stress, Psychological
chemical_list: D009270:Naloxone; D009020:Morphine