Acute effect of cholecystokinin on short-term synaptic plasticity in the rat hippocampus

Cholecystokinin (CCK), a peptide hormone found in the gut, is the most abundant peptide neurotransmitters in the brain, and its acute effects on the brain activity have been shown. In this study we aimed to evaluate the acute effects of CCK on short-term synaptic plasticity in the dentate gyrus (DG) of the rat hippocampus. Via stereotaxic surgery, the stimulating and the recording electrodes were placed in the perforant pathway and dentate gyrus, respectively and 30 min after intraperitoneal (i.p.) injection of CCK octapeptide sulfated (CCK-8S, 1.6 μg/kg), evoked responses were recorded after delivering of paired-pulse stimulations at 10 to 500 ms inter-stimulus intervals. With respect to the control group that received saline instead of CCK, in baseline responses, slope of field excitatory postsynaptic potential (fEPSP) 5 min and 10 min after injection of CCK-8S (p