Direct opioid application to peripheral nerves does not alter compound action potentials.

The identification of opiate receptors on primary afferent fibers near the dorsal root ganglia suggests that opiates may be able to affect conduction in primary afferent nerve fibers. We examined the effect of directly applied, preservative-free morphine sulfate (0.1 mg/kg) and fentanyl citrate (25 micrograms/kg) on the A beta, A delta, and C components of the compound action potential of the superficial radial nerve in decerebrate cats (n = 18). Neither drug caused any significant change in the area under the curve of any of the compound action potentials studied. These data indicate that systemically administered opiates are unlikely to cause changes in primary afferent nerve conduction.