The current results demonstrate a greater inhibitory effect of EM-1 on the inflammatory response to electrical nerve stimulation (58% inhibition) compared to SP (34% inhibition) suggesting the involvement of both pre- and post-terminal mechanisms in the inhibitory modulatory actions of EM-1. Evidence is provided for the involvement of opioid receptors in this inhibitory effect. The results also suggest that EM-1 is equipotent in inhibiting the inflammatory response under different injury conditions.