Systemically administered cholecystokinin affects an evoked potential in the hippocampal dentate gyrus

Cholecystokinin was administered systemically while recordings were taken of the evoked action potential in the hippocampal dentate gyrus to stimulation of the medial entorhinal cortex. The sulphated octapeptide and t. BOC CCK-4, but not the unsulphated octapeptide or tetrapeptide, increased the amplitude of the evoked action potential in a dose-dependent manner, whereas the unsulphated octapeptide decreased it. Bilateral vagotomy did not block the effect of the sulphated octapeptide. CR 1409 was also found to increase the amplitude of the evoked response and did not block the effect of subsequent administration of sulphated octapeptide. These results are consistent with action at a central receptor locus.