Effect of intrahippocampal administration of vitamin C and progesterone on learning in a model of multiple sclerosis in rats.

Purpose: The purpose of this study was to evaluate the effect of intrahippocampal injection of vitamin C and progesterone, alone or in combination, on passive avoidance learning (PAL) in multiple sclerosis. Methods: Sixty- three male wistar rats were divided into nine groups (n=7) as following: control (saline), lesion, vitamin C (0.2, 1, 5 mg/kg), progesterone (0.01, 0.1, 1 μg/μl) and combination therapy. Lesion was induced by intrahippocampal injection of ethidium bromide. In combination therapy, animals were treated with vitamin C (5 mg/kg) plus progesterone (0.01 mg/kg). Animals in experimental groups received different treatments for 7 days, and then all groups were tested for step through latency (STL). Results: Our results showed that intrahippocampal injection of ethidium bromide destroys PAL significantly (p<0.001). Treatment with vitamin C (5mg/kg) significantly (p<0.05) improved PAL. Lower doses of progesterone did not affect latency but dose of 1 μg/μl significantly (p<0.05) increased STL. In combination therapy group STL was significantly (p<0.05) more than in the lesion group, although it was not significantly different from the vitamin C group. Conclusion: Based on our results, we concluded that intrahippocampal injection of vitamin C improves memory for PAL, but progesterone alone or in combination with vitamin C had no improving effects on memory.