THE USE OF AUTORADIOGRAPHIC TECHNIQUES FOR THE IDENTIFICATION AND MAPPING OF TRANSMITTER-SPECIFIC NEURONES IN THE BRAIN

Abstract

This chapter discusses the use of autoradiographic techniques for the identification and mapping of transmitter-specific neurons in the brain. In homogenates of rat brain tissue from various regions labeled noradrenaline appears to be taken up predominantly into synaptosome particle. This has been confirmed in laboratory by electron microscopic autoradiography of homogenates of rat cerebral cortex and striatum incubated with 3 H-nor adrenaline. On this basis, 5% of all the synaptosomes were labeled in homogenates of the cerebral cortex and 16% were labeled in homogenates of the striatum. The latter value is in close agreement with the estimate of 16.4% given by Hokfelt as the proportion of dopaminergic terminals in the rat caudate nucleus, based on the cytochemical staining of dense-cored vesicles after loading striatal slices in vitro with noradrenaline or with α-methyl- noradrenaline. It has proved possible to retain the neutral amino acids, GABA, glycine, leucine, and alanine after administration of the tritiated amino acid by fixation of tissues with buffered glutaraldehyde. The estimation of the radioactivity present in fixed tissue offers a simple guide to the probable exposure period necessary for the production of sufficient silver grains to make autoradiography feasible.