Autoradiographic visualization of haloperidol-sensitive sigma receptors in guinea-pig brain

The distribution of sigma receptors in guinea-pig brain is demonstrated using quantitative autoradiography and the new selective sigma receptor probe, 1,3-di(2[5-(3)H]tolyl)guanidine. Pharmacological analysis, using slide-mounted brain sections, reveals that this site is saturable and has a drug-specificity profile similar to that found in homogenate binding studies. Autoradiography reveals a moderate to high density of discrete, specific labeling superimposed on a lower level of homogeneous 1,3-di(2[5-(3)H]tolyl)guanidine binding. Both patterns are displaced by incubation with 10 microM haloperidol or 1,3-di-ortho-tolyl-guanidine. In the forebrain, the highest density of binding is associated with the magnocellular-neuroendocrine and limbic systems; lower densities are distributed in non-limbic nuclei and the lowest levels occur in the extrapyramidal system. In the midbrain and hindbrain, motor nuclei involved in voluntary and involuntary motor behavior are discretely labeled, as are many of the cranial nerve nuclei. The anatomical distribution of the haloperidol-sensitive sigma receptors is distinct from the pattern of phencyclidine receptors and suggests sigma compounds may effect endocrine, emotional and motor behavior.