A method of screening a compound or a composition for use in modulating opioid withdrawal symptoms in a mammal. The method comprises the steps of: selecting a group of test animals; separating the group into two subgroups; inducing Panx1 activation or expression in both subgroups; dosing a first subgroup with a candidate compound; dosing a second subgroup with a placebo; measuring ATP released in spinal microglia of test animals in the first subgroup and in the spinal microglia of test animals in the second subgroup; quantifying the difference in ATP released in spinal microglia of test animals in the first subgroup and in the spinal microglia of test animals in the second subgroup; if the difference in the ATP released in the first subgroup and the APT released in the second subgroup is greater than 25%, then formulating the candidate compound into a pharmaceutical composition.