Endogenous opioids are involved in abnormal stereotyped behaviours of tethered sows.
Tethered sows continuously performed stereotypies during a substantial part of the day time. A single subcutaneous injection with naloxone significantly decreased the profound stereotypies, while explorative behaviours of pigs were not affected by naloxone. In addition a long-term effect of naloxone was noticed. It is suggested that performing the seemingly purposeless stereotypies may function as an effective strategy in order to cope with the conflict-inducing housing conditions. The present data implicate endorphins in this strategy. The involvement of endorphins in the stereotypies of the sows may be related to the calming, rewarding and dependency-inducing effects of the endorphins.
D000818:Animals; D004723:Endorphins / Q000502:physiology*; D005260:Female; D009270:Naloxone / Q000494:pharmacology; D012149:Restraint, Physical; D013239:Stereotyped Behavior / Q000502:physiology*; D013552:Swine
D004723:Endorphins; D009270:Naloxone