Interaction of thiocolchicoside with [H-3]strychnine binding sites in rat spinal cord and brainstem

Radioreceptor binding assays and receptor autoradiography were used to investigate the activity of thiocolchicoside on strychnine-sensitive binding sites in rat brain and spinal cord using [H-3]strychnine as a ligand. Thiocolchicoside displaced the binding of [H-3]strychnine with an affinity similar to that of unlabeled glycine, and showed a Hill coefficient and proportionality parameter (P) less than unity. The activity of thiocolchicoside toward [H-3]strychnine binding sites was confirmed in autoradiographic studies. The results suggest that thiocolchicoside behaves as an allosteric compound acting on the strychnine-sensitive glycine receptor in rat brainstem and spinal cord, and that this interaction may provide a possible mechanism for the myorelaxant activity of this colchicoside derivative, the first clinically useful drug acting on this receptor.