Comparing the effects of crocin at different doses on excitability and long-term potentiation in the CA1 area, as well as the electroencephalogram responses of rats under chronic stress

Stress adversely affects the cellular and electrophysiological mechanisms of memory; however, crocin has beneficial effects on brain functions. Nonetheless, the electrophysiological effects of using this active saffron component at different doses are not yet studied in rats under chronic restraint stress. Therefore, this study compared the impact of crocin at different doses on the excitability and long-term potentiation (LTP) in the CA1 area of rats, as well as their electroencephalogram (EEG) responses, hippocampal and frontal cortical glucose levels under chronic restraint stress (an emotional stress model). Forty rats were allocated into five groups of control, sham, restraint stress (6 h/day/21 days), and two stress groups receiving intraperitoneal injections of crocin (30, 60 mg/kg/day). Besides measuring the slope and amplitude of field excitatory postsynaptic potentials (fEPSPs) in the input–output and LTP curves, the EEG waves and hippocampal and frontal cortical glucose levels were assessed in all groups. Chronic restraint stress significantly decreased the fEPSP slope and amplitude in the input–output curves and after LTP induction. Both doses of crocin (60 and particularly 30 mg/kg) significantly improved fEPSP slope and amplitude in the stressed groups. Also, stress and crocin only at a dose of 30 mg/kg altered the EEG waves. Hippocampal and frontal cortical glucose levels displayed no significant differences in the experimental groups. Crocin at doses of 60 mg/kg/day and particularly 30 mg/kg/day reversed the harmful effects of chronic restraint stress on LTP as a cellular memory-related mechanism. However, only the lower dose of crocin affected the electrical brain activity in EEG.