Effects of Crocin on Learning and Memory in Rats Under Chronic Restraint Stress with Special Focus on the Hippocampal and Frontal Cortex Corticosterone Levels

Chronic stress adversely infl uences brain functions while crocin, as an effective component of saffron, exhibits positive effects on memory processes. This study investigated the effects of different doses of crocin on the improvement of learning and memory as well as corticosterone (CORT) levels in the hippocampus and frontal cortex of rats subjected to chronic stress.

Forty male rats were randomly allocated to fi ve different groups (n = 8): Control, sham; stress (6 h/day for 21 days) groups, and two groups receiving daily intraperitoneal injections of one of two doses (30 and 60 mg/kg) of crocin accompanied by 21 days of restraint stress. Latency was evaluated as a brain function using the passive avoidance test before and one-day after a foot shock. CORT levels were measured in the homogenized hippocampus and frontal cortex.

Results revealed that chronic stress had a signifi cantly (P < 0.01) negative effect on memory. Crocin (30 and 60 mg/kg), however, gave increase to signifi cantly (P < 0.01 and P < 0.05; respectively) improved memory functions in the stressed rats. Furthermore, the CORT levels in the hippocampus and frontal cortex declined signifi cantly (P < 0.05) in the stress group compared to the control. Only a crocin dose of 30 mg/kg was observed modulate signifi cantly (P < 0.05) the CORT levels in the hippocampus and frontal cortex in the stressed group.

It was found that the lower crocin dose (30 mg/kg) had more benefi cial effects than its higher (60 mg/kg) dose on learning and memory under chronic stress conditions. Moreover, it was speculated that different doses of crocin act on different neurotransmitters and biochemical factors in the brain.