Properties of two benzodiazepine binding sites in spinal cord.

Two types of benzodiazepine receptors were demonstrated in spinal cord. Binding to one of these sites (neuronal) was sensitive to the centrally active benzodiazepine, clonazepam, and binding was enhanced both by chloride and GABA. The second site was sensitive to 7-chloro-1,3-dihydro-1-methyl-5-(p-chlorophenyl) 2H-1,4-benzodiazepine-2-one (R05-4864) and thus is similar to the site characteristic of non-neuronal tissue. Binding to the neuronal site was inhibited by the putative glycine antagonist, strychnine, both in spinal cord and brain. This inhibition may account for the reported anti-GABAergic properties of strychnine and does not appear to be related to the glycine receptor.