Effects of tianeptine on the performance of a reaching movement in the cat.

Unlike other antidepressant drugs, tianeptine, when administered to cats at doses ranging from 1.2 to 5 mg/kg, produces an increase in arousal associated with longer sequences of immobile attentiveness. The present study analyses tianeptine-induced effects on visuomotor performance. Cats were trained to perform a pointing movement towards a randomly moving spot of light. Following tianeptine treatment (5 mg/kg), visuomotor performance was totally disrupted. When 2.5 mg/kg tianeptine was used, the accuracy of performance was unaffected, whereas the latency of movement onset was considerably and consistently increased. On a number of occasions the movement took also longer to perform. Following lower doses (0.6-1.2 mg/kg), performance was rarely impaired; in contrast, an improvement of visuo-motor scores was observed. This improvement was mostly characterized by an increased accuracy and could be associated with shorter latencies of movement onset or shorter movement times. Desipramine, another antidepressant drug having few sedative effects, induced a clear delay of movement onset when first administered. Further injections did not produce any changes in the visuo-motor performance. These results are discussed in relation with other effects of tianeptine, in particular its facilitatory effect on attentional processes.

[Modification of the strategy of intentional movement after lesions of the substantia nigra in the cat]. / Modification de la stratégie d'un mouvement intentionnel après lésion de la substance noire chez le chat.

Bilateral lesions of the substantia nigra were carried out in cats previously overtrained at performing a visually guided forepaw movement towards a moving target. Both their reaction time (RT) and movement time (MT) were impaired postoperatively. On the other hand, their pointing precision was unimpaired after lesion and even improved relative to the preoperative level. This improved accuracy persisted even when the duration of the movement had returned to normal. It is suggested that lesioned animals develop and keep a new strategy using visual feed-back throughout the movement, while normal cats, even on such a complex pointing task, mainly use visual information to trigger their movement.