Effects of high frequency-repetitive transcranial magnetic stimulation on pattern visual evoked potential and vasoactive intestinal peptide expression in visual cortex of rats with amblyopia

Abstract

Aim To explore the effects of high frequency-repetitive transcranial magnetic stimulation (hf-rTMS) on pattern visual evoked potential (PVEP) and vasoactive intestinal peptide (VIP) expression in visual cortex of rats with amblyopia and to preliminarily discuss the underlying mechanism of action. Methods Thirty SD rats aged 3 weeks were randomly selected and equally divided into the normal control group (NC), monocular deprivation group (MD), and monocular deprivation + hf-rTMS group (MD + hf-rTMS). Rats in the NC group were not intervened. Rats in the MD and MD + hf-rTMS groups were used to establish an amblyopia model by suturing the lid in the right eye for 3 weeks, while rats in the MD + hf-rTMS group were further intervened by two weeks of hf-rTMS. PVEP was tested in the right eye of rats at 6 and 8 weeks of age. Rats at 8 weeks of age were sacrificed, and the left visual cortex was extracted for immunohistochemistry (IHC) and in situ hybridization (ISH) examinations. Results At 6 weeks of age, there was no significant difference between the MD and MD + hf-rTMS group in terms of the P100 wave (P < 0.05). Besides, in comparison to the NC group, both the two groups had a distinct reduction in P100 amplitude (P < 0.05) and a prolonged latency (P < 0.05). At 8 weeks of age, the P100 amplitude in the MD + hf-rTMS group increased evidently than that in the MD group (P < 0.05). As compared to the NC group, the MD + hf-rTMS group had a remarkably lower P100 amplitude (P < 0.05). No distinct difference was found in the latency between the MD + hf-rTMS group and the MD or NC group (P > 0.05). IHC and ISH analyses demonstrated that VIP was expressed in all groups, and the mean OD value and the number of VIP-positive cells in the MD + hf-rTMS group were significantly higher than those in the MD group (P < 0.05) but distinctly lower than those in the NC group (P < 0.05). Conclusion hf-rTMS could increase the VIP expression in visual cortex and improve visual transduction in rats with amblyopia.The mechanism of hf-rTMS may be to participate in the remodeling of the visual system by improving the expression of VIP