Effects of crocin on cognitive and spatial memories in rats under chronic isolation stress

Introduction: Certain types of chronic mental stress impair memory. On the other hand, crocin is introduced in the medical literature as an effective component of saffron with remedial effects on memory impairment. This study investigated the effects of crocin on spatial and cognitive memories, locomotor activity, novel recognition conditions and serum corticosterone levels in rats under chronic isolation stress. Methods: Male rats were randomly allocated to the five groups of control, sham, isolation stress (St.I), St.I-C30 and St.I-C60. The latter two groups were exposed to chronic isolation stress (6h/day) receiving two levels of crocin (30 and 60 mg/kg, respectively) over a period of 21 days. The object location and novel object recognition tests (OLT and NOR) were used to evaluate spatial and cognitive memories, respectively. Results: The OLT results revealed that chronic isolation stress led to significantly decreased locomotor activity in all the stressed groups; the NOR test, however, yielded similar results only in the St.I group. Moreover, isolation stress was found to lead significant declines in spatial and cognitive memories. Finally, crocin administration led to improvements in impaired memory in St.I-C30 and St.I-C60 groups. There were significant enhancements in serum corticosterone levels in the St.I and St.I-C30 groups as compared with the control group. Conclusion: Our findings indicate that spatial and cognitive memory impairments are strongly affected by isolation stress and crocin especially at its high dose of 60 mg/kg, exhibits better protective effects against cognitive memory deficit induced by chronic isolation stress.