New peptide mechanism of auriculo-acupuncture electro-analgesia: role of angiotensin II.

In rabbits, auriculo-acupuncture electrostimulation with frequencies of 15 and 100 Hz induced an analgesic effect expressed by a decrease in the amplitude of a cortical somatosensory evoked potential in response to tooth pulp electrostimulation. Intracerebroventricular saralasin injection abolished or blocked the effect of auriculo-acupuncture stimulation at 100 Hz, but not at 15 Hz frequency. Intravenous injection of naloxone abolished the effect of auriculo-acupuncture stimulation at 15 Hz but not at 100 Hz frequency. Methysergide or D,L-p-chlorophenylalanine injection diminished but did not entirely block the effect of auriculo-acupuncture stimulation at 100 Hz. This suggests that the neuropeptide angiotensin II is a antinociceptive factor in dental peptide analgesic mechanisms induced by auriculo-acupuncture stimulation at 100 Hz frequency.