EXCITOTOXIC LESIONS OF THE PEDUNCULOPONTINE TEGMENTAL NUCLEUS DISINHIBIT OROFACIAL BEHAVIORS STIMULATED BY MICROINJECTIONS OF D-AMPHETAMINEINTO RAT VENTROLATERAL CAUDATE-PUTAMEN

Data are presented which support the hypothesis that the pedunculopont ine tegmental nucleus serves as an output station for the striatum and , in particular, has a role in the expression of behaviour stimulated from the ventrolateral caudate-putamen, a rodent homologue of the prim ate putamen. Rats received either bilateral ibotenate or sham lesions in the pedunculopontine tegmental nucleus and bilateral cannulation of the ventrolateral caudate-putamen. Oral motor activities were observe d following microinjection of 5.0, 10.0 and 20.0 mu g d-amphetamine (a nd vehicle-only control) into the ventrolateral caudate-putamen. As ex pected, orofacial behaviours such as biting and licking were observed in sham-lesioned rats following this treatment, but pe dunculopontine tegmental nucleus-lesioned rats exhibited an increase in the incidence of these oral motor be haviours at all doses of amphetamine compared with the duration and number of times in which they engaged in oral mo tor behaviours, but not the latency to initiate them. There was no cha nge in the normal oral motor activities associated with grooming. Hist ological analysis showed that ibotenate lesions destroyed both choline rgic and non-cholinergic neurones in the pedunculopontine tegmental nu cleus. These data indicate that loss of the pedunculopontine tegmental nucleus disinhibits oral motor behaviours stimulated from the ventrol ateral caudateputamen by d-amphetamine and are discussed in terms of t heir implications for understanding the relationships between striatal outflow and structures in the pens.