Abstract
BackgroundThe purpose of this study was to evaluate the antinociceptive effect of black raspberry (Rubus occidentalis) fruit extract (ROE) in a rat model of chronic muscle pain and examine the mechanisms involved.MethodsAdult male Sprague–Dawley rats were used, and chronic muscle pain was induced by two injections of acidic saline into one gastrocnemius muscle. For the first experiment, 50 rats were randomly assigned to five groups. After the development of hyperalgesia, rats were injected intraperitoneally with 0.9 % saline or ROE (10, 30, 100, or 300 mg/kg). For the second experiment, 70 rats were randomly assigned to seven groups. Rats were injected intraperitoneally with saline, yohimbine, dexmedetomidine, prazosin, atropine, mecamylamine, or naloxone after the development of hyperalgesia. Ten minutes later, ROE (300 mg/kg) was administered intraperitoneally. For both experiments, the mechanical withdrawal threshold (MWT) was evaluated with von Frey filaments before the first acidic saline injection, 24 h after the second injection, and at 15, 30, 45, 60, 80, 100, and 120 min, 24 and 48 h after the drug administration.ResultsCompared with the control group, the MWT significantly increased up to 45 min after injection of ROE 100 mg/kg and up to 60 min after injection of ROE 300 mg/kg, respectively. Injection of ROE together with yohimbine or mecamylamine significantly decreased the MWT compared with the effect of ROE alone, while ROE together with dexmedetomidine significantly increased the MWT.ConclusionsROE showed antinociceptive activity against induced chronic muscle pain, which may be mediated by α2-adrenergic and nicotinic cholinergic receptors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1192-z) contains supplementary material, which is available to authorized users.
Highlights
The purpose of this study was to evaluate the antinociceptive effect of black raspberry (Rubus occidentalis) fruit extract (ROE) in a rat model of chronic muscle pain and examine the mechanisms involved
Two injections of pH 4.0 saline into one gastrocnemius muscle 2 days apart resulted in a bilateral decrease in the mechanical withdrawal threshold (MWT) (Fig. 1)
Experiment 1 An intraperitoneal injection of 300 mg/kg of R. occidentalis extract (ROE) resulted in a significant increase in the MWT at 15, 30, 45, and 60 min bilaterally, compared with control group (p = 0.001,
Summary
The purpose of this study was to evaluate the antinociceptive effect of black raspberry (Rubus occidentalis) fruit extract (ROE) in a rat model of chronic muscle pain and examine the mechanisms involved. After the development of hyperalgesia, rats were injected intraperitoneally with 0.9 % saline or ROE (10, 30, 100, or 300 mg/kg). For both experiments, the mechanical withdrawal threshold (MWT) was evaluated with von Frey filaments before the first acidic saline injection, 24 h after the second injection, and at 15, 30, 45, 60, 80, 100, and 120 min, 24 and 48 h after the drug administration. Chronic pain and hyperalgesia induced by musculoskeletal injuries are managed using a multidisciplinary approach, but can be disabling and difficult to treat [1]. Studies have reported antinociceptive effects of other Rubus species [9, 10]
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