Transient supression by stress of haloperidol induced catalepsy by the activation of the adrenal medulla.

Rats were injected with haloperidol (0.5-1.0 mg X kg-1). When the catalepsy score was almost maximal (60 s, measured by the bar-test), the rats were handled, exposed to cold (3 degrees C) or immobilized. After each of these stress procedures the catalepsy was significantly reduced. Handling of adrenalectomized rats gave no such reduction. Infusion of adrenaline (10 nmol X kg-1, given in 15 s), in contrast to that of isoprenaline and phenylephrine (both the same concentration as adrenaline) also reduced the haloperidol induced catalepsy. These findings indicate that neuroleptic catalepsy in rats is not only mediated through central but also through peripheral mechanisms, e.g. by the adrenal medulla.