CHOLECYSTOKININ (CCK-8S) PROLONGS UNSATURATED THETA-PULSE INDUCED LONG-TERM POTENTIATION IN RAT HIPPOCAMPAL CA1 IN-VITRO

The effects of bath-applied sulphated cholecystokinin octapeptide (CCK-8S; 500 nM) and the selective CCKB receptor antagonist PD 135158 (1 mu M) on the induction and maintenance of an 'unsaturated' long-term potentiation (LTP) were examined using recordings of field excitatory postsynaptic potentials (fEPSP) and population spikes (PS) in the hippocampal CA1 region of the rat. LTP was induced by a single theta-pulse stimulation (10 pulses at 7 Hz) of the Schaffer collateral-commissural pathway. CCK-8S had minor effects on the induction of LTP but substantially prolonged LTP of both fEPSP and PS from about 1 to at least 3 h. The antagonist PD 135158 had no influence on the induction of potentiation of fEPSP slope, but decreased the potentiation of PS amplitude. The results su ppo rt the view that CCK-8S may facilitate long-term changes in glutamatergic synaptic transmission of the hippocampus, such as LTP.