A simple and economical method of electrode fabrication for brain self-stimulation in rats.

Introduction: Intracranial self-stimulation (ICSS) is an operant paradigm in which rodents self-administer rewarding electrical stimulation through electrodes implanted into the brain. We describe a simple, inexpensive and reliable method to fabricate monopolar and bipolar electrodes, along with the swivel system, for delivery of electric pulses at the targeted sites in the brain of rat.

Methods: The system consists of an insulated stainless steel wire(s) (diameter: 0.25 mm), plastic base, pedestal and connector attached to a swivel via a stimulating cable, which is connected to the stimulator. We provide the specifications, source of each component, and the method of fabrication in details.

Results: In-house fabricated monopolar or bipolar electrodes were subjected to rigorous tests. We implanted the electrode into the medial forebrain bundle (MFB) and rat was trained to press the lever for electrical self-stimulation in operant chamber for 60 min each day. In about 3-4 days, the animal gave a consistent response (~40 presses/min) and was considered as conditioned. For evaluation of reinforcement behavior, the number of lever pressings of conditioned rat with or without electrical stimulation was assessed for a period of 30 min each day for 10 weeks. The rewarding frequency sustained for the entire duration. In addition, we compared the lever pressing data of the groups of rats implanted with in-house fabricated versus with those with commercial electrodes; no significant differences were encountered.

Discussion: The required components for the electrode fabrication are easily available. With some practice, the system can be easily assembled in the laboratory and costs less than a dollar. We suggest that the electrodes, fabricated using this method, may serve as an economical and reliable tool in neuropharmacological and neurobehavioral studies.