Time‐dependent changes in bladder function and plantar sensitivity in a rat model of fibromyalgia syndrome induced by hydrochloric acid injection into the gluteus

Abstract

What’s known on the subject? and What does the study add? Bladder pain syndrome/interstitial cystitis (BPS/IC) and fibromyalgia syndrome (FMS) often occur concomitantly. In this study, we found that somatic (gluteus)‐to‐visceral (bladder) cross sensitization might underlie bladder hypersensitivity in patients with FMS. OBJECTIVE • To examine the correlation between muscular pain and bladder hypersensitivity in order to clarify the pathogenesis of comorbidity of bladder pain syndrome/interstitial cystitis with other chronic pain conditions such as fibromyalgia syndrome (FMS). MATERIALS AND METHODS • Under isoflurane anaesthesia, 0.2 mL of hydrochloric acid (HCl) solution (pH 4.0) was injected into the bilateral gluteus muscles of female Sprague–Dawley rats to produce an FMS model, as the gluteus is one of the specific tender points in patients with FMS. Control rats received saline injection (0.2 mL). • The mechanical sensitivity of the plantar was evaluated using the mean number of bilateral hindlimb withdrawals in response to tactile stimulation with a 2.0‐g von Frey filament at 1, 2 and 3 weeks after the HCl injection. • In a separate rat group, cystometry was performed with the rats awake during saline infusion (0.06 mL/min) into the bladder before and after 1% lidocaine injection (0.2 mL) into the bilateral gluteus 1, 2 and 3 weeks after the HCl injection. RESULTS • The mean number of hindlimb withdrawals was significantly higher in FMS rats than in controls at 1 and 2 weeks. • Using cystometry, we found that the intercontraction interval (ICI) and voided volume (VV) were significantly lower in FMS rats than in controls at 1 and 2 weeks. In addition, the voiding threshold pressure, ICI and VV were significantly higher after lidocaine injection in FMS rats, but not in controls, at 1 and 2 weeks. CONCLUSIONS • HCl injection (pH 4.0) into the gluteus can induce plantar hypersensitivity and urinary frequency for up to 2 weeks after the injection, suggesting that somatic (gluteus)‐to‐visceral (bladder) cross‐sensitization might underlie bladder hypersensitivity in patients with FMS. • Moreover, intervention at specific tender points outside the bladder could be effective in treating urinary frequency because lidocaine injection into the gluteus normalized bladder function in FMS rats for up to 2 weeks.

Excessive exercise induces cardiac arrhythmia in a young fibromyalgia mouse model

“…To investigate effective treatments for FM patients, FM-induced animal models have been made for basic animal research. FM was initially induced by acidic saline injection [21], hydrochloric acid injection [22], or intermittent cold stress [23]. However, these animal models showed comparative recovery within two weeks.…”

Modelos animales de dolor para el estudio de la fibromialgia

“…Taking stress as one of the main symptoms of fibromyalgia patients, Khasar et al 41 devised the DCG model, which consists of inducing stress through unpredictable sounds. Furuta et al 46 devised the FMS model, SVI/CI, with an intramuscular injection of HCl, pH 4 bilaterally in the gluteal muscles and an injection of intravesical polyethylene catheter + + 1% lidocaine. Green et al 41 proposed the model of FMS, SVI, anxiety, and temporomandibular disorder.…”

Transient receptor potential A1 receptor‐mediated neural cross‐talk and afferent sensitization induced by oxidative stress: Implication for the pathogenesis of interstitial cystitis/bladder pain syndrome

“…In other reports, a rat model with surgically‐induced endometriosis had reduced micturition thresholds and increased Evans Blue dye extravasation in the bladder, suggesting that bladder hypersensitivity and inflammation might be induced by uterine irritation as a result of endometriosis 32 . Recently, we also have shown that a rat model of FMS induced by HCl injection into the gluteus 33 showed plantar hypersensitivity and bladder overactivity, suggesting the possibility that somatic (gluteus muscle)‐to‐visceral (bladder) cross‐sensitization might underlie bladder hypersensitivity in patients with FMS 34 …”