The distribution of glycine receptors in the human brain. A light microscopic autoradiographic study using [3H]strychnine.

Glycine receptors were localized autoradiographically in postmortem human brain material using [3H]strychnine as a ligand. Slide mounted tissue sections were labeled in vitro by incubation with [3H]strychnine and autoradiograms obtained using [3H]Ultrofilm. Receptor densities were quantified by computer assisted microdensitometry. No specific binding of [3H]strychnine was observed in any of the forebrain areas studied. Low densities were seen in the midbrain except for dorsal and lateral parts of the periaqueductal grey matter and the oculomotor nuclei. In pons, medulla oblongata and upper cervical cord high densities of [3H]strychnine binding sites were associated with some nuclei including the motor and sensory trigeminal nuclei, the facial and the hypoglossal nuclei. The highest densities of grains were associated with the substantia gelatinosa of the trigeminal nucleus in the medulla oblongata. A peculiar spotty distribution of [3H]strychnine binding sites were found in the gracilis and cuneatus nuclei. The distribution of glycine receptors in the human brain is comparable to that seen in the rat brain, although densities are much higher in the rat. The distribution of glycine receptors in the human brain provides an anatomical substrate for the understanding of the effects of drugs acting in these receptors, particularly strychnine.