 Hypothesis: Surgically-induced inflammation will temporarily reduce blood-brain barrier drug efflux transporter function in proportion to the degree of inflammation. The investigators anticipate that inflammation-mediated reductions in drug transporter function will be reflected by an increased cerebral spinal fluid CSF concentration of morphine a PGP substrate and M3G and M6G MRP1 substrates. The corresponding in vitro studies will allow us to elucidate the mechanisms by which inflammation alters blood brain barrier efflux transport of morphine, M3G and M6G. 