AN INVESTIGATION INTO THE ROLE OF THE PEDUNCULOPONTINE TEGMENTAL NUCLEUS IN THE MEDIATION OF LOCOMOTION AND OROFACIAL STEREOTYPY INDUCED BYD-AMPHETAMINE AND APOMORPHINE IN THE RAT

As the pedunculopontine tegmental nucleus has an important anatomical position as an output station for the striatum, its role in the mediat ion of behaviour stimulated by d-amphetamine and apomorphine was inves tigated. Bilateral ibotenate lesions were made in either the pedunculo pontine tegmental nucleus or, as a control, in the adjacent deep mesen cephalic nucleus; sham lesions were made using phosphate buffer. Over the 14 days after surgery there were no significant differences in the rats' body weight or food intake. Deep mesencephalic lesioned rats sp illed more food and drank more water (never more than 5 mi more) than controls or pedunculopontine tegmental lesioned rats. Spontaneous loco motion and that elicited by d-amphetamine or apomorphine were not affe cted by ibotenate lesions of either the pedunculopontine tegmental nuc leus or deep mesencephalic nucleus. At higher doses of d-amphetamine a nd apomorphine, however, excessive biting and licking were observed in the pedunculopontine tegmental nucleus, but not deep mesencephalic nu cleus, lesioned rats. Such orofacial stereotypies are never observed i n normal rats after systemic injection of d-amphetamine. Post mortem a nalysis showed that ibotenate lesions of the pedunculopontine tegmenta l nucleus had destroyed cholinergic and non-cholinergic neurons there but had left the deep mesencephalic nucleus intact; ibotenate lesions of the deep mesencephalic nucleus destroyed neurons in that structure but not the pedunculopontine tegmental nucleus. These data demonstrate that lesions in the pedunculopontine tegmental nucleus and deep mesen cephalic nucleus have different effects, measured histologically and b ehaviourally; that neither spontaneous locomotion nor that stimulated by d-amphetamine or apomorphine is dependent on the integrity of the p edunculopontine tegmental nucleus; and that the pedunculopontine tegme ntal nucleus plays an important role in mediating orofacial activity s timulated by these drugs. The data are discussed in terms of their imp lications for understanding outflow from the caudate-putamen and nucle us accumbens.