Active avoidance is impaired correlated with changes of spontaneous behaviour after lesions of the lateral parabrachial nucleus of rat.

Open field (OF) behaviour, active avoidance (CAR) acquisition and the neurological status of 14 male hooded rats of the Long-Evans strain were compared before and after bilateral electrocoagulation of the lateral parabrachial nucleus (PB1). The PB1 lesion syndrome was characterized by significantly more square crossings in spite of more grooming and significant longer duration for immobility in the OF. The exploratory activity was strongly reduced. PB rats moved more quickly, whenever they performed ambulation. The habituation quotient for ambulatory activity was insignificantly decreased but for exploratory activity significantly increased. PB rats were able to reproduce preoperatively learnt CAR in the Y-maze but not in the jump test and could not postoperatively acquire a new avoidance stereotype. The results indicate an important participation of PB1 in response selection and CAR acquisition.