A simple design for a small fixed four-electrode brain stimulation array

Anatomical studies of intracranial self-stimulation (ICSS) reward in rats often use the lesion method and, therefore, require repeated behavioral testing before and after the lesion. Other anatomical studies on unlesioned rats use a moveable electrode to permit testing at a number of ICSS sites. Combining these methods would yield still more information, but repeated testing is not possible due to the damage created by lowering the electrode. To meet this need, an array of 4 fixed vertically-spaced electrodes was devised. Electrodes are constructed from strands of 0.14-mm (0.0035'') Teflon-insulated stainless-steel wire, 4 of which are glued into an implantable bundle. A 4-channel IC rotary switch is implanted on the rat's head to permit the use of an inexpensive 2-channel electrode lead and commutator. In our laboratory, electrodes were vertically spaced at 0.3 mm, spanning die dorsoventral extent of the lateral hypothalamus and yielded stable rate-frequency curves over the usual 3-4 month period of behavioral testing.