Effects of anti-CCK-8 antiserum on acquisition and retrieval by mice in an appetitive task

Endogenous cholecystokinin (CCK) was blocked in the posterior cingulate cortex of BALB/c mice using a local injection of anti-CCK-8 antiserum, and memory effects were tested using Go-No Go visual discrimination conditioning. Injection of 0.4 microliter of anti-CCK-8 antiserum diluted to 1:10, 10-15 min before each session, produced substantial learning impairment on the discrimination task. But when injections were stopped, animals began to learn the task normally, showing that the anti-CCK antiserum effect was reversible. When the antiserum was administered at the same dose before a single test session 14 days after the end of the initial training, the retrieval process was also disturbed. These results show that cingulate cholecystokinin is essential for memory processes and suggest that cholecystokinin octapeptide may be a neuromodulator of the thalamo-cingulate pathway of Papez's circuit, which is involved in memory processes.