Low Field Magnetic Stimulation Ameliorates Schizophrenia-Like Behavior and Up-Regulates Neuregulin-1 Expression in a Mouse Model of Cuprizone-Induced Demyelination

Abstract

White matter and myelin sheath integrity are disrupted in schizophrenia, and non-invasive magnetic brain stimulation targeting these tracts is a promising new therapeutic approach. In particular, deep-brain reachable low field magnetic stimulation (DMS) could alleviate cognitive impairment and depressive-like behaviors in animal models. In this study, we sought to assess the effects of DMS on myelin sheath damage and schizophrenia-like behaviors in the cuprizone-induced demyelination mouse model. Mice were fed cuprizone (copper ion chelating agent, 0.2% w/w mixed with food) for 6 weeks to induce demyelination. During these 6 weeks, mice were stimulated with either sham, low-frequency (LFS, delta frequency) DMS or high-frequency (HFS, gamma Hz) DMS for 20 min each day. Behavioral tests were conducted 24 h after the final DMS session. The myelin sheath was examined by immunohistochemistry and the expression of neuregulin-1 (NRG1)/ErbB4 in the prefrontal cortex was measured with Western blotting. Six weeks of HFS significantly alleviated schizophrenia-like behaviors in cuprizone mice, including improved nesting, social interaction and sensorimotor gating, while LFS improved sensorimotor gating only. HFS and LFS both repaired the myelin sheath and increased the expression of neuregulin-1 and its receptor ErbB4, in the prefrontal cortex of demyelinated mice. Our findings show that DMS is a potential effective neuromodulation technique for the treatment of schizophrenia. One possible mechanism underlying these therapeutic effects could involve the up-regulation of NRG1/ErbB4 signaling in the prefrontal cortex.

Keywords: low field magnetic stimulation; myelin sheaths; neuregulin-1; neuromodulation; schizophrenia.

Figure 1

Schematic illustration of the DMS apparatus and stimulus patterns used in this study. (A) The apparatus and operational principle of DMS. (B) The stimulus pattern of LFS with delta rhythm. (C) The stimulus pattern of HFS with gamma rhythm.

Figure 2

Body weight, nesting, and locomotion are altered by cuprizone and partially rescued by DMS. (A) Weight changes in mice subjected to different treatments. (B) Representative images of nests built by control (a), model (b), LFS (c), and HFS (d) mice. (C) Histogram of nesting scores. (D) Total movement distance in 10 min. (E) Center zone movement distance in 10 min. Values are expressed as mean ± SEM (n = 12–15). ^**P < 0.01 vs. control group; ^#P < 0.05 vs. model group.

Figure 3

Social behavior is impaired by cuprizone and rescued by DMS. Results of the social interaction test are shown in (A–D). (A) Photo of the three-chamber apparatus used for the social interaction test. (B) Representative movement traces of (a) control mice, (b) model group, (c) LFS group, and (d) HFS group. (C,D) Histograms showing time spent in each side chamber in trials 1 and 2. (E,F) Histograms showing the distance traveled in proximity to the wire cages containing stranger mice or the empty cage in trial 1. Values are expressed as mean ± SEM (n = 12–15). ^*P < 0.05, ^**P < 0.01, ^***P < 0.001.

Figure 4

PPI deficits in cuprizone mice are rescued by DMS. (A) Startle amplitude for all PPI test epochs. (B) PPI at 75 dB with 100 ms interval. Values are expressed as mean ± SEM (n = 12–15). ^**P < 0.01 vs. control group; ^#P < 0.05, ^##P < 0.01 vs. model group.

Figure 5

DMS restores myelination defects due to cuprizone. Effects of 6 weeks of DMS treatment on MBP protein expression are shown. MBP staining in cortex is shown in (A–D). (A) Control group. (B) model group. (C) LFS group. (D) HFS group. MBP staining in the striatum is shown in (E–H). (E) Control group. (F) Model group. The blue arrow points to the lateral striatum. (G) LFS group. (H) HFS group. MBP staining in the hippocampus is shown in (I–L). (I) Control group. (J) Model group. The blue arrow points to the dentate gyrus. (K) LFS group. (L) HFS group. Scale bar = 100 μm. (M) Western blot and quantitative analysis of MBP expression in the prefrontal cortex and hippocampus. β-actin was used as an internal control. Values are expressed as mean ± SEM (n = 4–5). ^*P < 0.05 vs. control group; ^#P < 0.05 vs. model group.

Figure 6

DMS treatment restores deficient NRG1 and ErbB4 expression in cuprizone mice. (A,B) Western blot and quantitative analysis of (A) NRG1 and (B) ErbB4 protein levels in the prefrontal cortex of mice. The upper figure shows the Western blot. β-actin was used as an internal control. The bottom panel is a histogram of the quantitative values from the corresponding blot. Values are expressed as mean ± SEM (n = 4). ^*P < 0.05 vs. control group; ^#P < 0.05, ^##P < 0.01, ^###P < 0.001 vs. model group.