Antinociceptive effect of acetaminophen in low frequency tail shock vocalization test in male NMRI rats

The present study was a protocol for investigation of the effect of acetaminophen (i.p.) on pain induced by electrical stimulation. We used tail shock vocalization (TSV) test for measurement of the pain. In this test, the animals were restrained and stimulated by two electrode implanted on the middle of the animal’s tail. The latency from stimulation of the tail till vocalization of the animal was measured and considered as pain scoring. We used high (80 Hz) and low (3 Hz) frequency stimulation in TSV test. Application of the acetaminophen at doses of 200 and 400 mg/kg could not produce a significant anti-nociceptive effect in high frequency TSV, but the pain induced by low frequency TSV markedly diminished at doses of 200 and 400 mg/kg of acetaminophen. Therefore, it is concluded that acetaminophen as an analgesic drug can attenuate low-frequency (3 Hz) TSV-induced pain