Neuroleptic-induced emotional defecation: effects of pimozide and apomorphine

Neuroleptics, such as haloperidol, have been found to produce dysphoria, anxiety and akathisia in humans. In animals, these effects have rarely been reported since the decreased movement produced by these drugs can confound the study of many behavioral indices of emotionality. In fact, most investigators have found a decrease in emotional defecation in rats given neuroleptics in novel environments, supporting their action as a major tranquilizer. We have found, however, that in rats a profound increase in emotional defecation can result from haloperidol administration in well habituated environments, such as the homecage. In male rats, defecation was measured for a one hour test period following various doses of the neuroleptic, pimozide, and the dopamine receptor agonist, apomorphine. Apomorphine and pimozide (a dopamine receptor antagonist) were both found to increase levels of fecal boli excretions. In addition, when apomorphine was combined with haloperidol, defecation levels were also increased suggesting that this phenomenon is not directly mediated by dopamine receptors. It is suggested that this drug-induced defecation is a consequence of the agent's interaction with the affective state of the animal, creating a dysphoric or anxious state in the animal.