Pharmacological potential of Baccharis dracunculifolia in the control of emotional-like comorbidities in chronic pain

• Author(s): Laranjeira, Inês Martins
• Date: 2017
• Persistent ID: https://hdl.handle.net/1822/50050
• Origin: RepositóriUM - Universidade do Minho
• Document Type: Master thesis
• Language: English
• Contributor(s): Universidade do Minho; Dias, Alberto Carlos Pires; Pinto-Ribeiro, Filipa

Description

In osteoarthritis (OA) the progressive degeneration of articular structures persistently activates nociceptors leading to chronic pain. Chronic pain is often accompanied by the comorbid development of emotional impairments, including anxiety and depression, an effect recently associated to changes in the activation level of microglia in the brain. Baccharis dracunculifolia DC (Asteraceae) (Bd) is a Brazilian medicinal shrub, popularly known as "Alecrim do Campo", shown to be an important source of active compounds with anti-stress and anti-inflammatory ability. After assessing its phytochemical profile, B. dracunculifolia antioxidant activity was evaluated using several in vitro models: free radical scavenging (DPPH method), iron chelating activity (ICA), NO and SO scavenging with quercetin used as a reference standard. The ability of B. dracunculifolia extract in reversing the OA-induced nociceptive and emotional impairments was studied in ovariectomized adult female rats (Rattus norvegicus, vr. albinus, wistar) using the kaolin/carrageenan (K/C) model. Four weeks after OA induction, mechanical hyperalgesia was confirmed and the pharmacological treatment started. Control animals (SHAM) were administered PBS while ARTH animals either received PBS or B. dracunculifolia 50mg/kg (Bd50) and 100 mg/kg (Bd100), via gavage, daily for five weeks. At the end of the treatment, anxiety-like behaviour was determined using the Open Field Test (OFT), anhedonia using the sucrose preference test (SPT) and learned helplessness using the forced swimming test (FST). Animals were then euthanized, the brains excised, preserved and sectioned. Activated microglia was stained with IBA-I and quantified in brain slides of target areas (Prefrontal Cortex, amygdala and periaqueductal gray matter) Our phytochemical analysis showed the Bd extract mainly contains phenolic compounds which is in accordance with its significantly higher activity in scavenging SO radicals. Treatment with Bd extract reversed OA-induced mechanical hyperalgesia and partly reversed anxious and depressive-like behaviour in ARTH animals concomitant to a decrease in the number of brain activated microglia. Our findings suggest Bd extracts can potentially be used as adjuvants in the management of OA-induced pain and associated emotional comorbidities.