Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 24-month-old rats

The brain-derived peptidergic drug Cerebrolysin has been found to support t he survival of neurones in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clin ical trails. In the present study, the effects of Cerebrolysin and its pept ide preparation E021 on the synapse density in the hippocampus, the dentate gyrus and in the entorhinal cortex of 24-month-old rats were investigated. Rats received the drugs or saline for control for 19 consecutive days (2.5 ml/kg per day). Slices of the brains were immunohistochemically stained wi th anti-synaptophysin, which is a specific marker of presynaptic terminals. Quantification of the synapse density was done by using light microscopy a nd a computerised image analysing system. Our results clearly showed that t he rats benefit from the administration of both drugs, showing an enhanceme nt in the number of synaptophysin-immunostained presynaptic terminals in th e entorhinal cortex, the dentate gyrus, and also in the hippocampal subfiel ds CA1, CA2, CA3 stratum lucidum and CA3 stratum radiatum. It can be assume d that these effects are the reason for improved cognitive performances of rats treated with Cerebrolysin and E021.