Acute application of cholecystokinin and its effect on long-term potentiation induction at CA1 area of hippocampal formation in rat

Introduction: It has been demonstrated that cholecystokinin sulfated octapeptide (CCK-8s) can affect synaptic transmission in the hippocampus. Because one of the major experimental models to understand the events happening in synaptic plasticity is To Study the long-term potentiation (LTP), we decided to investigate the effect of concomitant administration of CCK-8s and tetanic stimulation of Schaffer collateral path-CA1 synapses on LTP induction and maintenance. Materials and Methods: Experimental groups were control, CCK-5min and CCK-30min. CCK-8s was injected 5 or 30 min (1.6 mu g/kg; i.p.) prior to induction of LTP. The stimulating and the recording electrodes were placed in the Schaffer collateral pathway and hippocampal CA1, respectively. LTP was induced by 100 Hz tetanization and field excitatory postsynaptic potentials (fEPSP) slope, area and amplitude were measured and compared during 30 minutes Interval before, and 90 minutes Interval after LTP induction in each group. Results: The results showed that maintenance of the induced LTP was significantly improved in the CCK-30min group comparing to the control group. This improvement was particularly visible in the fEPSP slope (p<0.001) and the fEPSP area (p<0.001). Seventy minutes after the LTP induction, fEPSP was similar in both the CCK-5min and the CCK-30min groups and there was Also a significant difference between the treated groups comparing to the control group (p<0.05). Conclusion: These results indicated that LTP induction and maintenance is carried out effectively, at higher levels of CCK in the brain. The data suggest that CCK-8s has pronounced effects on synaptic plasticity in the hippocampus and the consequent cognitive functions.