Neuropharmacological actions of Pluchea indica Less root extract in socially isolated mice

Abstract

The effects of Pluchea indica Less root extract (PI-E) on locomotor activity and pentobarbital-induced sleep, social isolation-induced aggressive behavior, motor coordination in the rotarod test, pentylenetetrazole-induced convulsion and nociceptive responses in the tail-pinch test were examined in mice. Socially isolated mice showed higher locomotor activity and shorter duration of pentobarbital sleep than group-housed mice. PI-E (50-100 mg/kg, p.o.) significantly decreased locomotor activity and prolonged pentobarbital sleep in a dose-dependent manner in isolated mice but not in group-housed mice. At a large dose (400 mg/kg, p.o.), PI-E not only decreased locomotor activity but also prolonged pentobarbital sleep in group-housed mice. The reference drug diazepam, at 0.5 mg/kg, also suppressed the locomotor activity in isolated mice but not in group-housed mice. Moreover, diazepam, at 0.1 and 0.5 mg/kg, significantly prolonged pentobarbital sleep in both isolated mice and group-housed mice. The effects of PI-E and diazepam on pentobarbital sleep in isolated mice were significantly attenuated by flumazenil (1 mg/kg, i.v.). PI-E (50-100 mg/kg), as well as diazepam (0.5-5 mg/kg, p.o.), dose-dependently suppressed social isolation-induced aggressive behavior, but it had no effect on pentylenetetrazole-induced convulsion, motor coordination in the rotarod test, or nociceptive response in the tail pinch test in group-housed mice. These results suggest that PI-E attenuates pathophysiological changes caused by social isolation stress in mice, and that the GABAergic system is partly involved in the action of PI-E on a social isolation-induced decrease in pentobarbital sleep.