A technique for recording from spinal neurones in awake sheep

A technique is described for implanting a chamber on 1 or 2 vertebrae of the spinal column of the sheep. This chamber protrudes permanently through the dorsal skin of the back and is covered by a light bandage. Between recording sessions the chamber houses an inner cap sealing the hole that gives access to the cord. During recording sessions this cap is removed and a miniature manipulator inserted instead. This manipulator can accept a motor drive that holds a glass-coated tungsten microelectrode. The drive has a hole through which an arthroscope tube can be passed so that insertion of the electrode can be performed under visual control. Extracellular recordings have been made of single spinal neurones for up to 4 h in animals that are drug-free, untrained and only lightly restrained. Recording sessions can be repeated on a daily basis for several weeks until the dura and/or arachnoid becomes too thickened to permit electrode penetrations. Animals remain healthy and their behaviour remains normal throughout this time.