Effects of repeated treatment with cholecystokinin sulfated octapeptide on passive avoidance memory under chronic restraint stress in male rats

BACKGROUND: Cholecystokinin (CCK), a peptide hormone found in the gut is the most abundant peptide neurotransmitter in the brain as well, and its effects on learning, memory, and anxiety have been shown. However, it is not clear whether this substance acts as a mediator for anxiety and stress induction or inhibits them. Hence, the purpose of this study was to evaluate the effects of CCK on memory function under stress conditions. MATERIALS AND METHODS: Male Wistar rats were divided into four groups: The control, the control-CCK, the stress, and stress-CCK. To induce stress, the rats were placed within adjustable restraint chambers for 6 h daily, for 24 days. CCK-8S (cholecystokinin sulfated octapeptide was injected before induction of stress (1.6 μg/kg, intraperitoneal) for 24 days. Passive avoidance learning test was used for evaluation of learning and memory. Rats received foot electrical shock before stress induction and CCK injection and step through latencies were evaluated 1-day after the last session of stress and treatments. RESULTS: Stress impaired memory significantly (P < 0.05). Although CCK per se decreased memory (P < 0.05), it prevented the memory impairments in the stress group as there was no significant difference between the control and stress-CCK groups. CONCLUSION: Stress has a profound effect on cognition and CCK probably acts as a mediator for its action. Our results showed that a high concentration of CCK during stress may be helpful in alleviating the effects of stress on the brain.