Role of 5-HT_5A receptors in the consolidation of memory

5-HT₅ receptor occurs in brain areas implicated in learning and memory. Hence, the effects (0.01-3.0mg/kg) of SB-6995516 (a 5-HT_5A receptor antagonist) in the associative learning task of autoshaping were studied. The results showed that post-training injection of SB-699551 decreased conditioned responses (CR) during short-term (STM; 1.5h; at 0.1mg/kg) and long-term memory (LTM; 24h; at 3.0mg/kg) relative to the vehicle animals. Moreover, considering that there are no selective 5-HT_5A receptor agonists, next, diverse doses of the serotonin precursor l-tryptophan were studied during STM and LTM, showing that l-tryptophan (5-100mg/kg) facilitated performance, particularly at 50mg/kg. In interactions experiments, l-tryptophan (50mg/kg) attenuated the impairment effect induced by SB-699551 (either 0.3 or 3.0mg/kg). All together this evidence suggests that the blockade of 5-HT_5A receptor appear to be able to impair STM and LTM (24h), while its stimulation might facilitate it. Of course further investigation is necessary, meanly with selective 5-HT_5A compounds are necessary.