Effect of Intermediate-Frequency Repetitive Transcranial Magnetic Stimulation on Recovery following Traumatic Brain Injury in Rats

Abstract

Traumatic brain injury (TBI) represents a significant public health concern and has been associated with high rates of morbidity and mortality. Although several research groups have proposed the use of repetitive transcranial magnetic stimulation (rTMS) to enhance neuroprotection and recovery in patients with TBI, few studies have obtained sufficient evidence regarding its effects in this population. Therefore, we aimed to analyze the effect of intermediate-frequency rTMS (2 Hz) on behavioral and histological recovery following TBI in rats. Male Wistar rats were divided into six groups: three groups without TBI (no manipulation, movement restriction plus sham rTMS, and movement restriction plus rTMS) and three groups subjected to TBI (TBI only, TBI plus movement restriction and sham rTMS, and TBI plus movement restriction and rTMS). The movement restriction groups were included so that rTMS could be applied without anesthesia. Our results indicate that the restriction of movement and sham rTMS per se promotes recovery, as measured using a neurobehavioral scale, although rTMS was associated with faster and superior recovery. We also observed that TBI caused alterations in the CA1 and CA3 subregions of the hippocampus, which are partly restored by movement restriction and rTMS. Our findings indicated that movement restriction prevents damage caused by TBI and that intermediate-frequency rTMS promotes behavioral and histologic recovery after TBI.

Figure 1

Effect of traumatic brain injury (TBI) and repetitive transcranial magnetic stimulation (TMS) on body weight and food intake. (a) Bars represent the mean ± SEM of daily body weight changes, measured 1 day before (P) and on days 1 to 7 after TBI. Data differed significantly according to day and experimental group; ^∗p < 0.05 versus control group (two-way ANOVA and Bonferroni's post hoc test). (b) Bars represent the mean ± SEM of food intake (g) measured 1 day before (P) and on days 1 to 7 after TBI. Data differed significantly according to day and experimental group; ^∗p < 0.05 versus control group (two-way ANOVA and Bonferroni's post hoc test).

Figure 2

Effect of movement restriction on bleeding and mortality following TBI. (a) Bars represent the mean ± SEM of bleeding after TBI; ^∗p < 0.05 (one-way ANOVA and Bonferroni's post hoc test). (b) Bars represent the mortality percentage at 8 days after TBI; p > 0.05, chi-square test.

Figure 3

Effect of traumatic brain injury (TBI) and repetitive transcranial magnetic stimulation (TMS) on neurological score. Bars represent the mean ± SEM of neurological score obtained 1 day before and on days 1 to 7 after TBI. Bars labeled with the same letter represent nonsignificant differences (Kruskal-Wallis and Kolmogorov post hoc tests).

Figure 4

Morphological changes in the CA1 subregion of the hippocampus represent the effect of traumatic brain injury (TBI) and repetitive transcranial magnetic stimulation (TMS). Photomicrographs of hippocampal area CA1 stained with cresyl violet. The magnification in the large image corresponds to 10x. Total magnification: 100x and the insets images in the upper right corner correspond to 40x. Total magnification: 100x. Sections are as follows: (a) R + TMS, (b) T, (c) T + R, and (d) T + TMS.

Figure 5

Effect of traumatic brain injury (TBI) and repetitive transcranial magnetic stimulation (TMS) on cellular CA3 morphology. Bright field photomicrographs of the hippocampal CA3 region stained with cresyl violet. Objective magnification: 10x. Total magnification: 100x. (a) C; (b) R; (c) R + TMS; (d) T; (e) T + R; (f) T + TMS.

Figure 6

Effect of traumatic brain injury (TBI) and repetitive transcranial magnetic stimulation (TMS) on cell dispersion and counting. (a) Bars represent the mean ± SEM of cell dispersion in the different hippocampal subregions (CA1, CA2, CA3, and dentate gyrus [DG]). Differences were only statistically significant in the CA3 subregion; p < 0.05 (Kruskal-Wallis and Kolmogorov post hoc test). (b) Bars represent the sum + SEM of cell counting in 3 different fields of CA1. (c) Bars represent the sum + SEM of cell counting in 3 different fields of CA3. ^∗p < 0.05 versus C, R, and R + TMS groups.