A Simplified Electrode-Assembly for Implanting Chronic Electrodes in the Brains of Small Animals

Abstract

Several techniques have been described for implanting multiple electrodes in the brains of large laboratory animals.1 With smaller animals, such as the rat and guinea pig, it is more diicult due to the limitations of space and to the fragility of the skull. For the past two years, we have used a method which enables us to place at least four electrodes in the rat's brain. Many of our Ss have been tested daily for periods in excess of one year, and the method has proven to be completely reliable. All components are easily accessible, and the assembly has the advantage of simplicity of construction and economy. The technique has proven to be equally useful for stimulation and for recording, and it is applicable to a wide variety of laboratory animals. Constrrtion of electrodes. The electrode-pedestal and the male-connector both are constructed from size 6-32 threaded nylon rods which can be purchased in convenient lengths.2 The nylon may be cut with a scalpel blade into approximately 5/16-in. segments. With larger animals, it is desirable to cut the nylon in 1/2-in. lengths. Two longitudinal holes, 0.032-in. (drill bit #67) in diameter, with centers 0.045 in. apart, are drilled through the nylon rods. It is desirable to place these holes at equal distances from the center, which can best be accomplished with the aid of a simple jig that holds the nylon rod and guides the drill bits. The point of a 21-gauge hypodermic needle is cut off with a fine emery wheel and then forced into one of the holes until approximately 1/4 in. extends out the opposite side. We have found 0.010-in. stainless steel wire,