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. 2024 Mar 27:17:1299-1311.
doi: 10.2147/JPR.S449750. eCollection 2024.

Effect of Sympathetic Blockade on Spontaneous Discharge and the H-Reflex at Myofascial Trigger Points in Rats

Shixuan Liu #  1 , Lin Liu #  1 , Xinyue Lu  1 , Tingfeng Yao  1
Affiliations

Effect of Sympathetic Blockade on Spontaneous Discharge and the H-Reflex at Myofascial Trigger Points in Rats

Shixuan Liu et al. J Pain Res. .

Abstract

Purpose: Myofascial trigger points (MTrPs) are the main cause of myofascial pain syndrome (MPS), and patients with MPS also have symptoms of sympathetic abnormalities. Consequently, this study aimed to investigate the potential relationship between MTrPs and sympathetic nerves.

Materials and methods: Twenty-four seven-week-old male rats were randomly divided into four groups (six rats every group). Groups I and II were kept in normal condition (n=12), and groups III and IV underwent MTrPs modelling (n=12). After successful MTrPs modelling, differences in sympathetic outcomes between the MTrPs groups (III and IV) and non-MTrPs groups (I and II) were observed. Sympathetic blockade was then applied to groups III and I (n=12). Data were collected on peak inversion spontaneous potentials (PISPs) and the H-reflex-evoked electromyography during spontaneous discharge at the MTrPs before and after sympathetic blockade.

Results: Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate were significantly higher in the MTrPs group than in the non-MTrPs group (P<0.05). Compared with group I, group III had the PISPs potential lower wave amplitude, shorter duration and amplitude-to-duration ratio, and lower H latency and latency difference H-M (P<0.05). Compared with group IV, group III had the PISPs potential lower wave amplitude, duration, amplitude-to-duration ratio, M-wave latency, H maximum wave amplitude, and maximal wave amplitude ratio H/M (P<0.05). The changes before and after sympathetic blockade in the MTrPs group were significant, and the amplitude, duration, and amplitude-to-duration ratio of the PISPs potentials were lower after the blockade (P<0.05).

Conclusion: MTrPs and sympathetic nerves interact with each other forming a specific relationship. MTrPs sensitize sympathetic nerves, and sympathetic nerve abnormalities affect local muscle myoelectric hyperactivity, leading to MTrPs. This finding is instructive for the clinical management of sympathetic disorders.

Keywords: H-reflex; electromyography; myofascial pain syndrome; myofascial trigger point; sympathetic blockade.

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Conflict of interest statement

The authors reports no conflicts of interest in this work.

Figures

Figure 1
Figure 1
Changes in various sympathetic outcomes after blockade (formula image, n = 24). (a) SBP, Systolic blood pressure. (b) DBP, Diastolic blood pressure. (c) MAP, Mean arterial pressure. (d) HR, Heart rate. *P < 0.05, **P < 0.01.
Figure 2
Figure 2
Excretion of NE in the urine of rats before and after sympathetic nerve blockade in the unblocked and blocked groups (formula image, n = 24). (a) Unblock groups (II and IV) (b) Block groups (I and III). ns P>0.05, ****P < 0.0001.
Figure 3
Figure 3
Characteristics of PISP images between groups of rats. (a) Group I :Non-MTrPs and sympathetic blockade modelling (b) Group II :Non-MTrPs and no sympathetic blockade modelling (c) Group III :MTrPs and sympathetic blockade modelling (d) Group IV :MTrPs and no sympathetic blockade modelling.
Figure 4
Figure 4
Comparison of outcomes of EMG in groups (formula image, n = 24). (a) Amplitude (b) Duration (c) Amplitude-to-duration ratio. *P < 0.05, **P < 0.01.
Figure 5
Figure 5
Comparison of EMG outcomes before and after sympathetic block in groups III and IV (MTrPs group) (formula image, n = 6). (a) Amplitude (b) Duration (c) Amplitude-to-duration ratio. **P < 0.01.
Figure 6
Figure 6
H-reflex in rats between groups. (a) Non-MTrPs and sympathetic blockade modelling (b) Non-MTrPs and no sympathetic blockade modelling (c) MTrPs and sympathetic blockade modelling (d) MTrPs and no sympathetic blockade modelling.
Figure 7
Figure 7
Comparison of H-reflex outcomes after blockade between groups (formula image, n = 24). *P < 0.05, **P < 0.01.
See this image and copyright information in PMC

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