Increased immobility in an automated forced swimming test following lesion of the habenula in rats: absence of evidence for a contribution from motor impairment.

The effects of lesions of the habenula on responses during a forced swimming test (FST) were examined. Active behavior, documented by turns on a drum immersed in a water tank, were reduced in lesioned rats. Lesioned rats also demonstrated an inability to escape from the water by climbing onto the drum when it was locked in position at the end of the test. There was a tendency for lesioned rats to show more activity in open-field tests either after the FST or independent of such prior testing. Lesioned rats showed no motor or postural abnormalities and were able to maintain position for longer than controls during a rotating rod test. Collectively, the results are compatible with the suggestion that lesions of the habenula impair the ability to change motor strategies under stress but indicate such failures may not be ascribed to gross motor impairment.