Chronic brain unit recording for pharmacological applications

Abstract

A technique is described in detail for chronic unit recording in awake, unrestrained animals during pharmacological manipulation. An example of the use of the technique is given with pharmacologically identified cells, behavioral tremor and how they are affected by anesthetics. The technique involves implantation of Nichrome wire electrodes into brain areas and anchoring them in an array on the skull. For recording, the electrode connectors on the skull are plugged into a light-weight field effect transistor (FET) amplifier the design of which is detailed. The FET amplifier is attached to a cable suspended from a counter-balanced commutator arm above the subject. This system allows subjects to move freely while unit activity from well isolated neurons or small groups of neurons is recorded. The technique allows long-term recording from the area of the electrodes over several weeks. Recording data obtained after harmaline injections and the slowing effects of different anesthetics on the rate of firing of units is presented.