INFLUENCE OF OLFACTORY STIMULATION ON NOCICEPTIVE BEHAVIOR IN MICE

The reactions elicited by nociceptive stimulations were studied in mic e exposed to the presence of different odors: positive (attractive), n egative (aversive), or neutral. In a first set of experiments, the ani mals were not habituated to the odors before the nociceptive stimuli w ere applied; in this case, the olfactory environment during experience d pain had essentially no effect on the nociceptive reactions, whateve r the nature of the odors. In a second set of experiments, the animals were habituated to the same odor for 20 days. The control group consi sted of mice habituated to and tested in the presence of the odor of t he laboratory. In that case, compared to controls, the neutral odor ha d no influence on nociceptive reactions. By contrast, the positive odo r decreased and the negative odor increased the reactions, especially when the intensity of the nociceptive stimulus was low. Moreover, it h as been shown that the reactions elicited during a second nociceptive stimulation period depend on the perception of pain animals experience during the first stimulation, which depended, in turn, on the odor as sociated with it. Results are discussed in terms of opioid-mediated in teractions between olfaction and pain. (C) 1997 Elsevier Science Inc.