STABLE FLY, STOMOXYS-CALCITRANS, MOUTHPART REMOVAL INFLUENCES STRESS AND ANTICIPATORY RESPONSES IN MICE

Biting fly attack induces a variety of stress and anxiety related chan ges in the physiology and behaviour of the target animals. Significant reductions in pain, or more appropriately, nociceptive sensitivity (l atency of a foot-lifting response to an aversive thermal stimulus), ar e evident in laboratory mice after a Ih exposure to stable flies, Stom oxys calcitrans. The role of the various components of biting fly atta ck in the development of this stress-induced reduction in pain sensiti vity (analgesia) is, however, unclear. This study demonstrates that fl y-naive mice do not exhibit a stress-induced analgesia when exposed to stable flies whose biting mouthparts have been removed. In contrast, mice that have been previously exposed to intact stable flies exhibit significant analgesia when exposed to flies that are incapable of biti ng. However, the level of analgesia induced is lower than that elicite d by exposure to intact stable flies. Exposure to non-biting house fli es, Musca domestica, has no effect on nociceptive sensitivity. It appe ars that the actual bite of the stable fly is necessary for the induct ion of analgesia and probably other stress and anxiety associated resp onses in fly naive mice. However, mice rapidly learn to recognize biti ng flies and exhibit significant, possibly anticipatory analgesic resp onses to the mere presence of biting flies.