Comparative study of the protective effects of crocin and exercise on long-term potentiation of CA1 in rats under chronic unpredictable stress

Abstract

Aim While stress causes brain dysfunction, crocin (as an active component of saffron) and exercise (as part of a healthy lifestyle) improve stress-induced memory impairment. The present study investigated the protective effects of crocin administration, exercise, and crocin-accompanied exercise on neuronal excitability and long-term potentiation (LTP) at the CA1 of hippocampus as well as serum corticosterone and glucose levels in rats subjected to chronic unpredictable stress (CUS). Main methods: Forty-eight male Wistar rats were randomly allocated to six groups: Control, Sham, CUS, CUS-Crocin30, CUS-Exercise, and CUS-Crocin30-Exercise. The chronic unpredictable stress and treadmill running at 20-21 m/min were applied 2 h/day and 1 h/day, respectively, for 21 days. Crocin (30 mg/kg) was daily intraperitoneally injected to the rats. Electrophysiological variables were recorded from the CA1 of hippocampus. While corticosterone and glucose levels were also measured. Key findings: CUS and CUS-Exercise significantly attenuated excitability and LTP. Compared to the CUS and CUS-Exercise treatments, CUS-Crocin30 and CUS-Crocin30-Exercise led to significant increases in slope and amplitude of field excitatory postsynaptic potential. The changes in serum corticosterone and glucose levels nearly matched the electrophysiological data. Significance: CUS was found to be a highly destructive stress as it failed to allow exercises to edify the CUS-induced memory deficit. This is while crocin (as a herbal drug) was found more effective than exercise (as a daily routine) in remedying the CUS-induced memory deficit. Also, although the treatment with crocin-accompanied exercise did help recovery from the CUS-induced memory deficit, the interaction of crocin administration and exercise had no synergic effects; the protective effect observed was due to crocin administration rather than the exercise.