Selective breeding of mice for high and low swim analgesia: differential effect on discrete forms of footshock analgesia

Abstract

Selective breeding of mice displaying high and low swim-induced analgesia led to the development of two animal lines divergent in the magnitude of analgesic response to swimming. In this study, animals belonging to the seventh generation of both lines were exposed to two temporally different forms of footshock, one of which produced opioid and the other non-opioid analgesia. We found that selective breeding for high and low swim-induced analgesia exerted a striking influence on the magnitude of the opioid-mediated type of footshock analgesia, but was ineffective on that of the non-opioid type.