Anti-stress, nootropic and anticonvulsant potential of fruit extracts of Piper longum L

An aqueous extract [AE] of fruits of Piper longum L. [PL] was investigated for its anti-stress activity in chronic cold restraint stress [(4±0.5 oC) for 1h daily for 7 days induced biochemical perturbations in Sprague Dawley rats. The nootropic potential of PL[AE] was assessed using a passive avoidance model and an elevated plus maze model in Swiss Albino mice. Further, the anticonvulsant activity of the extract was studied against seizures induced by pentylenetetrazole (PTZ), strychnine and 4-aminopyridine in mice. Stimulation of hypothalamus pituitary adrenal (HPA) axis in stressful condition alters plasma levels of glucose, triglycerides, cholesterol, total proteins and corticosterone. Pretreatment with the extract (250mg/kg and 500mg/kg p.o.) for 21 days significantly ameliorated the stress-induced biochemical perturbations in rats. PL[AE] treatment significantly increased step-down-latency and shortened the transfer latency in the passive avoidance model and the elevated plus maze model, respectively, suggesting nootropic potential. Further, treatment of groups with both doses offered protection against PTZ-induced convulsions but failed to protect against strychnine and 4-aminopyridine-induced convulsions in mice. Dimunition in gamma amino butyric acid (GABA) levels in brain of extract treated mice compared to vehicle treated mice learly indicated involvement of GABAergic mechanisms in the anticonvulsant activity. One-way ANOVA followed by Dunnett's or Bonferroni test was applied to verify statistical significance. The present study thus provides scientific support for anti-stress (adaptogenic), nootropic and anticonvulsant potential of an a aqueous extract of fruits of Piper longum in animal models.