Validity of a Method measuring Transmitter Release from the Central Nervous System

Abstract

Chase and Kopin¹ have recently shown that there may be serious limitations associated with techniques currently being used to investigate the release of potential neurotransmitter substances in the central nervous system. After intracisternal injection of radioactive noradrenaline or 5-hydroxytryptamine into rats, they were able to collect labelled compounds from the olfactory bulb using the push–pull cannula technique of Gaddum², and to show that peripheral stimulation with a variety of odours resulted in a marked increase in release of radioactivity. Chase and Kopin were unable to interpret these results as confirming indirect evidence that these amines may be transmitter substances in this area of the brain, because inert substances such as inulin or urea, when injected simultaneously with the amines, behaved in an identical manner. The authors rightly concluded, on the basis of these experiments, that measurements of the release of substances within the brain should be interpreted with caution, and that controls additional to those normally performed should be made.