Evidence for a role of haloperidol‐sensitive σ‐'opiate' receptors in the motor effects of antipsychotic drugs

Publisher Website
Google Scholar
Abstract
Haloperidol exhibits a high affinity for a subclass of σ-"opiate" binding sites which have a unique anatomic distribution and a unique drug selectivity pattern. These binding sites differ from phencyclidine-sensitive σ-receptors and are found in many brain areas involved in the control of movement. 1,3-Di-o-tolylguanidine (DTG), a highly selective ligand for the haloperidol-sensitive σ-receptor, produced marked dystonia in rats after micro injection into the red nucleus, a motor area rich in this receptor. Haloperidol and another σ-ligand [(+)-SKF 10,047] produced similar effects. On the other hand, clozapine, an antipsychotic drug which fails to bind to σ-receptors and fails to induce movement disorders in humans, failed to induce these dystonic reactions in rats. Phencyclidine was also without effect, as were injections of the active compounds in sites distant to the red nucleus. Microinjections of DTG in the substantia nigra produced vigorous contralateral circling behavior at extremely low doses. These findings suggest that σ-binding sites represent biologically functional receptors that are active in the neural control of movement. Since haloperidol (and many other antipsychotic drugs) exhibit an affinity for σ-receptors which is at least equal to its affinity for dopamine receptors, these data raise the further possibility that σ-receptors are involved in the motor side effects of antipsychotic drugs.