Abstract: Apparatus and methods for cooling and/or heating selected regions within a body are described herein. An implantable system is used to cool or heat nerve bodies down to about 15° C. to diminish nerve impulses. In one embodiment, the system can include an implantable unit containing a pumping mechanism and/or various control electronics. The system has a cooling element. The cooling element can be a Peltier junction or a catheter through which hot or cold fluid flows. The heated portion of the Peltier junction can be cooled by a liquid heat transfer medium which absorbs the heat from the junction and dissipates the heat elsewhere.