Journal of Pharmacy Research | Vol 11 • Issue 9 • 2017 1112 Neuroprotective role of Pterocarpus marsupium Roxb in streptozotocin-induced diabetic neuropathic pain in Type 2 diabetic rats Venkatesh Gunasekaran*, Merin Maria Mathew, Mrinmoy Gautam, M. Ramanathan INTRODUCTION Traditional medicines are generally derived from medicinal plants, minerals, and organic sources. Usage of herbal medicine in developing and developed countries has been increased nowadays due to their therapeutic benefits and less side effects. [1] One of the most common diabetic complication is diabetic neuropathic pain that occurs in approximately half of patients with diabetes. Diabetic neuropathy is characterized by progressive degeneration and impaired regenerative ability of peripheral nerve fibers, resulting in the progressive loss of the longest nerve fibers innervating the distal limb. [2] Despite the fact that the availability of modern and herbal medicine increased frequently in treating diabetes, yet the treatment of diabetes complications remains substantial challenge. Many studies revealed that controlled glycemia might reduce the risk of diabetes and diabetic complications, but few studies have reported that even with intensive insulin therapy or with conventional therapy, the incidence of neuropathy increased in patients with diabetes. [3] Various pre-clinical studies have also reported the beneficial effects of herbal products in the management of diabetic neuropathy such as Hypericum perforatum, Olea europaea, Curcuma longa, Emblica officinalis, and some clinical reports also believed to control the in neuropathic pain by the drugs of plant origin. [4-7] Pterocarpus marsupium Roxb (PM) (from the family: Leguminosae) known to have antidiarrheal, astringent, antacid, treatment of toothache, antidiabetic, antiarthritic, antigout, antiasthmatics, antihyperlipidemic, and treating bronchitis and skin infections. [8-10] PM is extremely rich in alkaloids and saponins possessing potential biological significance (Sharifi et al., 2003). Aqueous ABSTRACT Aim: The present study was aimed to evaluate the neuroprotective effects of aqueous extract of Pterocarpus marsupium Roxb (PM) on the pain threshold response in streptozotocin (STZ)-induced diabetic neuropathic pain. Material and Methods: STZ (40 mg/kg; i.p.) administered for 4 weeks in rats was monitored in 0 th and 8 th week by measuring blood sugar levels and body weight. Thermal hyperalgesia, mechanical hyperalgesia, and thermal allodynia were performed in 0 th , 4 th , 6 th , and 8 th week of the study. At the end of 8 th week study, formalin-evoked pain model followed by measurement of tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β and IL-6 level, and morphological changes in sciatic nerve were studied. All the rats except the vehicle-treated group received insulin 1 IU/kg/day to maintain plasma glucose levels. Results and Discussions: After 4 weeks of diabetic induction, administration of PM (100 and 200 mg/kg) along with 1 IU/day for 4 weeks had no significant effect on body weight and feed intake when compared to control rats. Pregabalin (10 mg/kg) and PM (100 mg/kg and 200 mg/kg) were injected for 4 weeks significantly attenuated the nociception in behavioral models. Furthermore, pregabalin and PM significantly inhibited the TNF-α, IL-1β, and IL-6 levels comparable to STZ group. In comparison to STZ with insulin- treated rats, PM exhibited significant increase in the pain threshold response. PM also reversed the STZ-induced axonal degeneration and deposition of collagen fibers in the sciatic nerve. Conclusion: The study concludes that neuroprotective effect of PM in STZ-induced neuropathic pain can be attributed to its anti-inflammatory and neuroregeneration mechanism. KEY WORDS: Histopathology, Inflammatory marker, Pterocarpus marsupium Roxb, Sciatic nerve, Streptozotocin Department of Pharmacology, PSG College of Pharmacy, Peelamedu, Coimbatore, Tamil Nadu, India *Corresponding author: Venkatesh Gunasekaran, Department of Pharmacology, PSG College of Pharmacy, Peelamedu, Coimbatore - 641 004, Tamil Nadu, India. Phone: +91-9791402846, Fax: 0422-2594400. E-mail: gvenkatpharma@gmail.com Received on: 07-07-2017; Revised on: 07-08-2017; Accepted on: 01-07-2017 Access this article online Website: jprsolutions.info ISSN: 0974-6943 Research Article