Serotonin, Septal Lesions, and Shock-Escape Learning in Rats

The involvement of reduced serotonin in deficient leverpress, shock-escape performance of rats with septal lesions was assessed in two studies. In Exp. 1, rats were treated with either para-chlorophenylalanine (PCPA) or saline and then tested in a leverpress, shock-escape task. In Exp. 2, rats with septal lesions and sham-operated control rats were treated daily with either 5-hydroxytryptophan (5HTP) or saline and tested on the same shock-escape task. Primary findings were as follows: (a) rats treated with PCPA learned to escape shock as quickly as saline control rats; (b) the shock-escape performance of rats with septal lesions was significantly inferior to that of control rats; and (c) the administration of 5HTP did not significantly improve the performance of either lesioned or control rats. These results suggest that the reduction of brain serotonin induced by septal lesions is not involved in the deficient shock-escape performance of septal-lesioned rats.

Discriminability and Procedure: Effects of Cocaine and Amphetamine

Rats were required to discriminate between central nervous system (CNS) stimulant drugs (cocaine and amphetamine) and saline. Experiments with cocaine involved two types of T-mazes. In one maze the incentive was escape from shock, in the other procedure the incentive was food. Cocaine discrimination occurred slowly or not at all in the shock-escape maze but fairly rapidly in the maze motivated by food and avoidance of shock. D-amphetamine was slowly discriminated in the T-maze, shock-escape procedure. These data raise the question of whether a single training procedure can be used to compare the discriminability of different classes of drugs.