Antinociceptive activity and effect of methanol extract of Salvia limbata on withdrawal syndrome in mice.

Objectives: Salvia (S.) is an important genus consisting of about 900 species in the Lamiaceae family. They are several reports that some Salvia spp. has effects on the central nervous system (CNS). The present experiments were undertaken to study the protective effect of S. limbata on the development of dependence to morphine in mice.
Material and Methods: Antinociceptive activity of aerial parts of S. limbata was investigated using the hot plate method. In addition, the effect of its aerial parts on morphine dependence was investigated in mice. After induction of dependence by morphine, different concentrations of plant aerial parts extract were injected to treated groups. To assess morphine withdrawal, mice were injected naloxone (5 mg/kg) i.p. on the 5th day. After four consecutive days of morphine injection, withdrawal syndrome was assessed by placing each mouse in a 30 cm high glass box and recording the frequency of escape jumps for 60 minutes.
Results: Animal receiving acute treatment with morphine displayed dependence. The animals treated with different extract concentrations could decrease frequency of escape jumps in number or decrease development of morphine dependence. Addiction was observed following naloxone administration. Methanol extract of S. limbata produced a statistically significant inhibition of pain induced by hot plate latency at 500, 1000 and 1500 mg/kg i.p. A significant increase in pain threshold was observed after 30 and 60 min (p < 0.001). The activity was comparable to that of morphine (30 mg kg(-1) i.p., p > 0.05). The anti-nociceptive activity of S. limbata increased until the 60th min (p < 0.05 compared to morphine).
Conclusions: S. limbata extract produced statistically significant inhibition of pain and development of morphine dependence in mice.