Analgesic activity of Nepeta italica L.

A screening study was performed on/by essential oils of Nepeta viscida Bois s and Nepeta italica L. using tail-flick and tail immersion (52.5 degrees C ) methods, N. italica samples were collected from three different localitie s of Turkey. Surprisingly, only one of the essential oils showed significan t activity, which was blocked by naloxone, indicating the involvement of op ioid receptors, This was seen only with the mechanical but not the thermal algesic stimulus, suggesting a specific activity on opioid receptors, exclu ding mu receptors. The same, active essential oil also exhibited a non-comp etitive inhibition of acetylcholine contractions of isolated rat ileum but it was inactive on the isolated rat aorta. Furthermore, a correlation betwe en the analgesic activity and the amount of 1,8-cineole was noticed. (C) 19 99 John Wiley & Sons, Ltd.