THE OPPOSITE EFFECTS OF CYSTEAMINE ON THE ACQUISITION OF 2 DIFFERENT TASKS IN MICE ARE ASSOCIATED WITH BIDIRECTIONAL TESTING-INDUCED CHANGES IN HIPPOCAMPAL ADENYLYL-CYCLASE ACTIVITY

The hypothesis of a role for hippocampal somatostatin (SS-14) in learn ing and memory processes was further examined by means of 2 selective learning tasks that were previously shown to be either impaired (spati al discrimination task) or facilitated (barpressing task) by hippocamp al lesions. Results showed that subcutaneous injections of cysteamine (160 mg/kg) (a) impaired acquisition of the spatial task while produci ng an opposite (i.e., facilitative) effect on acquisition of the barpr essing task and (b) produced an up regulation of hippocampal adenylyl cyclase (AC) activity, which was antagonized by spatial discrimination training but enhanced by training in the barpressing task. Moreover, opposite task-dependent training-induced changes in hippocampal AC act ivity was observed in saline-treated mice. These results suggest that bidirectional regulatory mechanisms of hippocampal function involving both SS-14 and ACs may occur as a function of the type of learning.