Experiments on hippocampal slices in rats showed that, in contrast to piracetam (100 µM to 10 mM), two new tripeptides, i.e. H-asparagil-glutamyl-proline-OH and H-asparagil-glutamyl-arginin-OH (concentrations 500 µM, 1 and 2.5 mM respectively), strengthened the orthodrome population responses in field СА1. In all three concentrations the effect of H-asparagil-glutamyl-proline-OH was stronger than of the other tripeptide. That is both tripeptides facilitate synaptic transmission within the Schaffer collaterals-pyramidal neurons system in hippocumpal field CA1. Similarly to piracetam (100 µM, within 15 minutes) these tripeptides supported short-term potentiation of the hippocampal synaptic transfer by N-methyl-D-aspartate (NMDA). Specific NMDA-receptors antagonist D-AP5 cancelled the NMDA effect fully which infers that the observed effect is achieved through activation of NMDA-receptors. Effect from H-asparagil-glutamyl-proline-OH excelled equally piracetam and H-asparagil-glutamyl-arginin-OH; H-asparagil-glutamyl-arginin-OH excelled piracetam only.
