Behavioral effects of anti-muscarinic, anti-serotonergic, and anti-NMDA treatments: hippocampal and neocortical slow wave electrophysiology predict the effects on grooming in the rat

Abstract

Previous research has shown that hippocampal and neocortical activation accompanies the postural changes occurring during self-grooming in rats but is absent or reduced during the stereotyped components of grooming, including head-washing and licking or biting. Since electrocortical activation is dependent on ascending cholinergic and serotonergic projections, we hypothesized that central muscarinic and serotonergic blockade would disrupt grooming by degrading cerebral control of changes in posture. Consistent with this, we find that systemic injections of scopolamine: (a) markedly reduce the occurrence of adaptive changes in posture during grooming; (b) reduce the probability of transitions from head-washing to body grooming; (c) reduce both the probability and duration of sequences of body grooming; and (d) do not affect the duration of head-washing or the probability of transitions from washing the snout to washing over the top of the head. Destruction of central serotonergic neurons with intracerebral injections of 5,7-dihydroxytryptamine increases the tendency of scopolamine to shorten the duration and increase the number of separate sequences of grooming. Systemic injections of a NMDA antagonist (CGS 19755) also impair grooming behavior. The data show that blockade of muscarinic and glutamatergic transmission impairs instinctive behavior as well as learned behavior and that the behavioral effects of muscarinic and serotonergic blockade are consistent with data obtained from the study of cortical slow wave electrophysiology.