On the mechanism of amphetamine-induced behavioural changes in the mouse. II. Effects of agents stimulating noradrenergic receptors.

The effects of three "noradrenergic stimulants", norepinephrine and alpha-methylnorepinephrine administered into the cerebral ventricles and of parenterally injected clonidine, have been observed on 18 separate items of dexamphetamine-induced behaviour in the mouse. Stereotyped behaviour was depressed by the "noradreneric stimulants" except for compulsive gnawing, which was markedly enhanced. Aspects of locomotor activity were enhanced except when compulsive gnawing was strong, at which time they were suppressed. Elements of heightened arousal were enhanced. It is suggested that these may be a positive noradrenergic component in the genesis of compulsive gnawing, locomotor activity and heightened arousal. The dominance of compulsive gnawing over certain other dexamphetamine-induced behaviours may lead indirectly to the suppressor effects of the noradrenergic stimulants on these behaviours.