Effects of pedunculopontine tegmental nucleus lesions on emotional reactivity and locomotion in rats

Abstract

Bilateral damage to the pedunculopontine tegmental nucleus (PPTg) has been found to impair several learning tasks; however, it is not clear whether this effect could be at least partially attributable to changes in the rat emotional reactivity and/or spontaneous locomotion. Therefore, the present work has tested the effects of bilateral electrolytic lesions of the PPTg on the behaviour of rats in the elevated plus-maze and the open field test. Because the behaviour of rats in learning and emotional tasks can be sensitive to routine experimental manipulations, we also have tested the effects of brief pre-surgical handling procedures on anxiety-like behaviours and locomotion in both lesioned and control rats. Lesions of the pedunculopontine tegmental nucleus (1) did not have any effects on spontaneous locomotor activity and (2) did not increase emotional reactivity. In fact, there was a slight bias towards a reduction in anxiety-like behaviours in lesioned rats, as evidenced by a significant increase in the number of open arm entries. Pre-surgical handling induced a slight decrease of emotional reactivity and a slight increase of exploratory activity. We conclude that damage to the pedunculopontine tegmental nucleus is not accompanied by either an enhancement of emotional reactivity or by an altered spontaneous locomotion.