Activation of the delta opioid receptor has been shown to produce pain-relief, and reduce anxiety and depression. For these reasons agonist to this receptor are currently being developed for clinical use. However, a deterrent to the development of these compounds, is that some delta opioid receptor agonists also produce convulsions, an adverse effect that has been observed across species. At the moment there is no way to predict whether a novel agonist will have this property. The goal of this work is to determine the mechanism that accounts for this difference between agonists that bind to the same receptor. These studies have important biological implications, and ultimately would increase the potential for delta opioid receptor agonists as novel drug therapies.