Cholecystokinin octapeptide increases passive avoidance latencies in rats.

Intraperitoneal injections of either 0.9% NaCl or cholecystokinin octapeptide (CCK-8) were paired with electrical footshock using a standard passive avoidance conditioning procedure for rats. Passive avoidance behavior was measured either 24 or 48 hr following the conditioning. No CCK-8 effect upon passive avoidance behavior was observed at the 24 hr test, but CCK-8 (100 micrograms/kg and 200 micrograms/kg) produced longer passive avoidance latencies at the 48 hr test. Control rats showed a decrease in passive avoidance latencies from 24 hr to 48 hr, while the CCK-8 rats did not show such a trend.