Linopirdine (DUP 996; AVIVA): Its effects in the morris water escape task and on retention of an incompletely acquired bar-press response in rodents

The present study assessed the effects of linopirdine, a putative cognition-enhancing drug, on the acquisition and retention of a bar-press response [continous reinforcement schedule (CRF)] in young Wistar rats. It was also investigated whether this substance influenced the acquisition and retention of a standard Morris water escape task by young NMRI mice and by young and old Wistar rats. Linopirdine was given subcutaneously (0.03, 0.1, 0.3, 1.0, or 3.0 mg/kg body wt.), 30 min before the first trial of a session and in one experiment immediately after the last trial of each session. A probe trial was given after the last acquisition session. In the CRF task, linopirdine did not affect the response latency and the 24-h retention of young rats. None of the parameters investigated in the Morris maze, including the escape latency (the time the animals need to find the platform), was affected by linopirdine in the rat and mouse experiments. This was also true for performance in the probe trial: linopirdine treatment did not affect the bias of the animals for the quadrant in which the platform had been positioned during acquisition. Thus, we found no experimental evidence for the hypothesized action of linopirdine as a cognition enhancer.