DIFFERENCES IN HIPPOCAMPAL SYNAPTIC PLASTICITY IN RATS WITH INBORN HIGH OR LOW LEARNING-ABILITY MAY BE RELATED TO DIFFERENT SENSITIVITY OF ASPARATATE RECEPTORS

Rats with an inborn high (HP) or low (LP) learning capacity were used to study the sensitivity to the blocking effect of 2-aminophosphonopentanoic acid (AP5; 10 and 20-mu-M) on long-term potentiation (LTP) produced in hippocampal slices by a 1-s tetanus at 200 Hz. The potential evoked by stimulation of the perforant path was recorded from the granule cell layer of the dentate gyrus in 400-mu-m slices perfused with standard Krebs' solution or the AP5. Under perfusion with 10-mu-M of AP5, in 100% of slices from HP rats, LTP generation was not blocked; when AP5 20-mu-M was used, in 85% of the cases LTP was not blocked. In 60% of slices from LP rats, AP5 10-mu-M and in 100% of the cases at 20-mu-M AP5 blocked LTP generation. These results are coherent with the hypothesis that the different inborn learning ability of HP and LP rats is related to the different population or sensitivity of N-methyl-D-aspartate (NMDA) receptors.