Inhibition of shaking movements in rats by central administration of cholinergic and adrenergic agents.

Shaking movements of the body, similar to that made by a dog when wet ('wet-dog shakes'), occur in rats in response to pharmacological stimuli and in response to stimuli associated with cold and skin irritation. In this study, shaking movements, elicited by a variety of stimuli, were inhibited by central administration of nanomolar doses of drugs that act as agonists on muscarinic, adrenergic, and opiate receptors. The brain regions that mediate the drug inhibition of shaking appear to be located in the medial preoptic area and in structures lining the aqueduct and fourth ventricle.