Pharmacological study of serotonin receptors in reward-directed behaviors

MICAELA BERNARDEZ VIDAL; MAXIMILIANO RAPANELLI; BONIFACIO SILVANO ZANUTTO; LUCIANA ROMINA FRICK

Cordoba Huerta Grande

Congreso; XXVI Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2011

Sociedad Argentina de Investigación en Neurociencia

The medial Prefrontal Cortex (mPFC), one of the brain structures that controls reward-dependant behaviors, expresses the serotonin (5-HT) receptors 5-HT1A, 5-HT2A and 5-HT3. Here we studied the effects on the performance of rats in a operant conditioning task of: a) 5-HTP, a 5-HT precursor; b) Buspirone, 5-HT1A agonist; c) Risperidone, 5-HT2A antagonist; and d) Ondansetron, an 5-HT3 antagonist. The administration of 5-HTP (50 mg/kg) did not affect the percentage of responses but increased the latency time to respond. Buspirone (10 mg/kg) had a similar effect, i.e., no differences in responses and highest latency times. Risperidone (1 mg/kg) completely blocked the learning of the operant conditioning task, evidenced in both parameters. Finally, Ondansetron (2 mg/kg) significantly reduced the number of responses, as well as the latency times. The 5-HT exerts a mainly inhibitory effect on the activity of the pyramidal neurons of the mPFC, given to the presence of 5-HT1A receptors in the axon hillock. 5-HT can also inhibit pyramidal neurons indirectly through the activation of 5-HT2A and 5-HT3 receptors localized in GABAergic interneurons. Therefore, these results indicate that the serotonergic circuit comprising the mPFC is involved in the learning of a reward-dependent task.