Intrahippocampal injections of cysteamine improve the retention of a bar-pressing task in mice

Cysteamine was used as a tool aimed at investigating the role of central so matostatin (SS-14) and was shown to modulate learning in a task-dependent m anner. However, direct arguments have not yet been provided to support the hypothesis that impairments and facilitation of learning produced by cystea mine are both mediated by the hippocampus. Mice were given daily intrahippo campal injections of artificial cerebrospinal fluid (C:SF) or cysteamine at doses of either 2.5 mu g/0.2 mu l or 25 mu g/0.2 mu l 1 h prior to each le arning session of a bar-pressing task, for which the acquisition was previo usly shown to be improved by systemic injections. The results showed that, with respect to (:SF, the: mice injected with cysteamine learned the bar pr essing task faster whereas no evidence of changes in locomotor activity was provided. Moreover, the results showed that retention was specifically inc reased in the two groups injected with cysteamine. It is argued that the ac tion of cysteamine on the hippocampus is sufficient to modulate specificall y learning-memory processes in a task-dependent manner. In conclusion, the blockade of some hippocampal information processing function by cysteamine is discussed to understand the bidirectional effects of drugs on learning a nd memory. (C) 1999 Elsevier Science B.V. All rights reserved.