Pain-related Post-exertional Malaise In People With Myalgic Encephalomyelitis/chronic Fatigue Syndrome And Fibromyalgia: A Meta-analysis

Abstract

PURPOSE: Chronic neuropathic pain(CNP) is clinically associated with the development of affective disorders such as anxiety and depression. However, the time course of CNP-induced depression symptoms remains unclear. This study set out to investigate the influence of CNP on depression-like behaviors at different periods. METHODS: CNP was induced using the model of sciatic nerve chronic constriction injury (CCI). To explore the behavioral tests at each time point after CCI, the mice were randomly assigned into the sham group and the CCI group. The CCI group was divided into six subgroups (n = 6 for each time point) at 7, 14, 21, 28,35, and 42 days after CCI, respectively. Mechanical allodynia was assessed using paw withdrawal frequency (PWF) by Von-Frey filaments (0.07g). The depression-like behaviors were examined using the forced swimming test (FST) and the tail suspension test(TST). All animal experiments were approved by the Laboratory Animal Welfare and Ethics Committee of Zhengzhou University. RESULTS: CCI mice at each time point display significantly higher basal paw withdrawal frequency (7d, 44.44%±4.12%; 14d, 48.89%±4.83%; 21d, 50.00%±4.71%; 28d,47.78%±5.21%; 35d, 42.22%±4.65%; 42d, 35.56%±2.94%) to Von-Frey filaments compared with the sham group (11.59%±2.51%,P<0.05). In the forced swim test, CCI mice spent significantly more time immobile on day 21 (135.86±27.56s), day 28 (139.6±21.29s), day 35 (155.86±21.36s), and day 42 (132.71±25.73s) than the sham group (79.18±25.96s, P<0.01). The time course of immobility in the tail suspension test was very similar to the result of FST. The immobility time of the CCI group on day 21(152.44±15.83s), day 28(148.29±29.84s), day 35(159.80±18.05s), day 42(132.71±25.73s) was significantly longer than that of the sham group(112.75±23.72s, P<0.05). CONCLUSIONS: These results demonstrated that three weeks of neuropathic pain induced depression-related behaviors. It indicates that intervention programs should be implemented in the early stage of pain to avoid depression, which has potential clinical implications.