Learning and retrieval are impaired after lesions of the ventral part of rat's nucleus reticularis pontis oralis.

Adult male hooded rats of the Long-Evans strain were investigated before and after lesions of the ventral nucleus reticularis pontis oralis (vRPO) in an open field test (OF) and in a Y-maze. The OF and the neurological findings were scarcely changed. Startle responses were strongly reduced and also horizontal head and body turning in the OF were significantly reduced. The retention of Y-maze avoidance tasks was reduced and relearning of the tasks relatively slow. Brightness discrimination remained unaffected by the lesion. The postoperative active avoidance learning of a new task in the jump test box was impossible. Postoperative learning of a thirst-motivated labyrinth task was significantly retarded compared with unoperated control rats. The vRPO lesion syndrome is quite different compared with 1 mm more dorsal (dRPO) and 1 mm more posterior (vRPC, dRPC) placed lesions and underlines the hypothesis of the functional heterogeneity of the pontine reticular formation.