A.S Bonsu 1, P. Amoateng 1*, K.A Bugyei 1
1 Department of Pharmacology & Toxicology, School of Pharmacy, 
College of Health Sciences, University of Ghana, P.O Box LG 43, Legon, Accra
*Corresponding author:pamoateng@ug.edu.gh

Introduction: Pain is a major symptom usually associated with most disease states. Its management still remains unsatisfactory despite the existence of many therapies, making it a global burden. Medicinal plants have been used since medieval times and are still being used today for treating some ailments. Desmodium adscendens is used traditionally for the treatment of epilepsy, pain and inflammatory conditions. However, data on its effect on pain is very scanty. This study sought to investigate the analgesic effect of an ethanolic extract of D. adscendens in rodents.

Method: The pulverized plant material of D. adscendens was extracted with 70%v/v ethanol by cold maceration. Chemical, thermal and neuropathic pain were induced in rodents. The possible mechanism(s) of analgesia of the extract were also investigated with receptor specific antagonists. 

Results and Discussion: The extract of D. adscendens (DAE) attenuated acetic acid-induced writhings (P=0.0012), ameliorated formalin-induced nociceptive pain in both the first (P=0.0058) and second phases (P= 0.0116), increased the %Maximum Possible Effect (MPE) in the hot plate test (P<0.0001) and significantly reduced paclitaxel-induced neuropathic pain in both thermal hyperalgesia ((P<0.0001) and cold allodynia (P=0.0024). 

The analgesic effect exhibited by DAE was significantly reversed in the presence of naloxone, glibenclamide, ondansetron, prazosin and yohimbine. By contrast, DAE’s, analgesic effects was not significantly affected in the presence of theophylline, atropine, L-Nitro-arginine methyl ester (L-NAME) and nifedipine. 

Conclusion: The ethanolic extract of D. adscendens exhibited profound analgesic effect against chemical, thermal nociception and paclitaxel-induced neuropathic pain. DAE may be utilizing the opioidergic, adrenergic systems and ATP-sensitive K+ channels and to some extent, the serotoninergic pathway to reduce pain.