Inhibition of spinal reflexes by acetylsalicylate and metamizol (dipyrone) in rats.

The effects of acetylsalicylate and metamizol on spinal monosynaptic reflexes were tested in spinal rats. Adult rats were anesthetized with ketamine, artificially ventilated, and spinalized at the C1 level. A laminectomy was performed in the lumbosacral region. Following electrical stimulation of the sciatic nerve by single pulses, the reflex potentials were recorded from the ipsilateral L5 ventral root. Acetylsalicylate was administered orally via nasogastric tube and metamizol intramuscularly. Acetylsalicylate (50 and 100 mg/kg) and metamizol (15 mg/kg) significantly decreased the amplitude of the reflex response (p < 0.05). But the 10-mg/kg metamizol dose did not significantly decrease the amplitude of the reflex response. The cyclooxygenase products of arachidonic acid may play an important role in regulating the reflex potential.