PDCD1 and fibromyalgia: PD-1 expression was normal in the normal group but significantly lower in the spinal cord of fibromyalgia mice (Figure 3A, 78.64 ± 2.11%, black column, * p < 0.05, n = 6), a decrease deepened by 2 Hz EA treatment (Figure 3A, 104.69 ± 4.80%, black column, # p < 0.05, n = 6).