In one of the inpatient psych wards I worked at, a new doctor came in with the ideal that IM lorazepam would better de-escalate belligerent patients than IM haloperidol. Nobody told the patients (all adolescents of ages 14-18) that a new stat sedative was being used, but over the course of several weeks I saw a sea change in the ward. Before lorazepam we'd have one or two incidents a week, usually with the same patients (about 25% of the total population). About 3 weeks into the lorazepam experiment, we'd have several incidents per day, and only about 10% of the patients refrained from outbursts.
Those who've worked at an inpatient facility will know what I mean. The staff would be lounging in the nurses' station when all of a sudden we'd hear saurian noises from some corner of the facility. Then the whole drill of all of us surrounding the possessed while one of the psychologists would attempt to talk him out of pulverizing the television set with the water fountain he'd just ripped out of the wall. The talking approach would often work during the haloperidol era, but it became absolutely futile when we started using the lorazepam.
Again, nobody told the patients we'd switched from haloperidol to lorazepam. Yet they'd sacrifice all their privileges and fracture their own bones to get the shot. I think the best answer to your question is that it just causes reward-seeking behavior, regardless of what hellish maze the rodent has to navigate.