Neuroleptic-induced emotional defecation: effects of scopolamine and haloperidol

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 neuroleptic administration in well habituated environments, such as the homecage. Anticholinergics are known to be effective in treating the side effects associated with neuroleptic administration in humans. Therefore the present study determined the effects of anticholinergic treatment in this animal model. In male rats, defecation was measured for a 1-h test period in their homecage following various doses of the central and peripheral anticholinergics, scopolamine, and n-methylscopolamine, respectively. A decrease in fecal excretions and an attenuation of haloperidol-induced defecation was found following administration of scopolamine. n-Methylscopolamine reduced defecation at all doses. When n-methylscopolamine was combined with haloperidol, both fecal mass and number decreased significantly. Since both anticholinergic agents reduced haloperidol-induced defecation it is suggested that their effectiveness is mediated through peripheral mechanisms.