Two types of chronic lead treatment in C57BL/6 mice: interaction with behavioural determinants of pain.
The male C57BL/6 mice used in this study were the offspring either of untreated or lead treated (0.1% lead acetate (PbAc) instead of drinking water) parents. Offspring of lead treated parents were reared on 0.1% PbAc until weaning, and also given 0.5% PbAc to drink for 3 weeks prior to testing (Pb2 group). Offspring of untreated parents were either given 0.5% PbAc to drink (Pb1 group) or maintained on tap water throughout (Control group). Control (C) and lead treated mice were subdivided according to single- or group-housing; no confrontation ("unfought") or confrontation with a trained aggressor mouse ("defeated"). All the mice were then given a hot-plate pain test, in which paw-lick and escape latencies were recorded. In untreated mice, latencies were reduced after defeat. This effect was not seen in lead treated animals. Lead treatment increased latencies in most instances relative to the appropriate control group. The paw-lick latencies were less consistently affected than the escape latencies. Escape latencies, with one exception, were longer in the Pb2 group than in the Pb1 group. Treatment with naloxone of single-housed C and Pb2 was without effect, except for Pb2 treated undefeated mice: here, naloxone abolished the analgesic effect of lead treatment. Lead-induced analgesia is discussed in terms of central mechanisms of pain reception.
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004291:Dominance-Subordination; D004723:Endorphins / Q000037:antagonists & inhibitors / Q000502:physiology; D004924:Escape Reaction / Q000187:drug effects*; D006799:Housing, Animal; D007854:Lead / Q000008:administration & dosage / Q000494:pharmacology / Q000633:toxicity*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009270:Naloxone / Q000494:pharmacology; D009942:Organometallic Compounds; D010146:Pain / Q000503:physiopathology*; D011930:Reaction Time / Q000187:drug effects*; D012934:Social Isolation
D004723:Endorphins; D009942:Organometallic Compounds; D007854:Lead; D009270:Naloxone; C008261:lead acetate