Antinociceptive, neurobehavioral and antioxidant effects of Eupatorium triplinerve Vahl on rats.

Ethnopharmacological Relevance: Eupatorium triplinerve Vahl belongs to the Asteraceae family, popularly known as Japana. It is a perennial shrub native to Amazon rainforests of South America. Its leaves are used through infusions, decoctions, baths, and tea. It is largely used in Brazilian folk medicine as sedative, febrifuge, stimulant, tonic and anti-inflammatory.

Aim Of The Study: The present study evaluated the putative effects of Eupatorium triplinerve on the central nervous system (CNS), including locomotor and anxiety activity, depression-like behavior, and antinociception and oxidative stress.

Materials And Methods: Two-month-old male Wistar rats (n=7-10 rats/group) and Swiss male and female mice of the species Mus musculus (n=7-10 per group) were administered with 100 mg/kg, 200 mg/kg, 400 mg/kg, 600 mg/kg, and 800 mg/kg of hydroalcoholic extracts of Eupatorium triplinerve (HEET). The behavioral assays included open-field (OF), elevated Plus-maze (EPM), and forced swimming tests (FS). The antinociceptive activity was verified using chemical (acetic acid and formalin) and thermal (hot plate) models of nociception. The oxidative stress levels were measured in rat blood samples after behavioral assays and Trolox equivalent antioxidant capacity (TEAC), nitric oxide and malondialdehyde (MDA) levels were measured in vivo.

Results: Oral pretreatment with HEET reduced the locomotion in OF test (200-800 mg/kg), increased central locomotion and open arms entries in the OF and EPM tests, respectively (600-800 mg/kg), and decreased the immobility time in the FS (200-800 mg/kg). It also reduced the writhing number evoked by acetic acid injection (200-800 mg/kg) and licking time in the first phase of the formalin test (400-800 mg/kg). In the oxidative stress assays, the extract decreased TEAC, Nitric Oxide and MDA levels in response to swimming stress induced in rats.

Conclusions: These results were indicative for the first time that Eupatorium triplinerve exerted mild sedative, anxiolytic and antidepressive effects on the CNS. Antinociceptive effects not related to opioid system and antioxidant activity were also observed. These results support the ethnopharmacological use of Eupatorium triplinerve in popular medicine.