Stimulation of 5-HT 1A receptors by systemic or medial septum injection induces anxiogenic-like effects and facilitates acquisition of a spatial discrimination task in mice

Abstract

1. 1. In the present study, the authors addressed the issue of the possible modulation of both emotional and learning processes by the stimulation of 5-HT A receptors. In this respect, we have carried out two series of experiments: the first series examined the effects of systemic injections of 8-OH-DPAT, a 5-HT 1A receptor agonist, successively on a model of anxiety and on a learning task; secondly the effects of selective infusions into the medial septum were studied in the same experimental design. 2. 2. Mice were tested in an elevated plus-maze before being submitted to a spatial discrimination task in an 8-arm radial maze. The 8-OH-DPAT (1mg/kg) administered intraperitoneally 30 minutes prior to testing, induced anxiogenic-like effects in the plus-maze and improved the acquisition of the spatial discrimination. 3. 3. Moreover, a regression analysis showed that the index of anxiety measured in the elevated plus-maze was positively correlated with the performance level reached at the forth day of training in the spatial discrimination task. The intraseptal infusion of the drug (1μg) demonstrated the same pattern of results, although the effects were less pronounced. Again a correlation between the index of anxiety and acquisition performance was obtained. 4. 4. These results suggest that anxiogenic-like effects induced by selective stimulation of 5-HT 1A receptors have a positive influence on the acquisition of a memory task. As systemic injections appeared to be more effective than intra-septal infusions, these effects might be mediated by both pre- and postsynaptic 5-HT 1A receptors.