A postmortem study of the effect of chronic opiate abuse on psychotomimetic binding sites of human frontal cortex

Autoradiographic distribution of sigma receptors in human neocortex, hippocampus, basal ganglia, cerebellum, pineal and pituitary glands

Autoradiographic distributions of [3H]1,3-di-O-tolylguanidine, [3H]DTG, binding to sigma (sigma) receptors were studied in key human brain regions. High densities occurred in the substantia nigra pars compacta and cerebellum. Pineal and pituitary levels were moderate. In neocortex, binding was high in laminae II-IVA and much lower in the midzone. Moderate binding occurred over hippocampal dentate granular cells and in the striatum. These results differ from those reported for the rodent.

Selective loss of cerebral cortical sigma, but not PCP binding sites in schizophrenia

Drugs such as phencyclidine (PCP) that interact with PCP and sigma binding sites can produce psychotomimetic effects that resemble some symptoms of schizophrenia. Therefore, it has been suggested that PCP and sigma receptors may be important in the clinical manifestations of schizophrenia. Assays of these two binding sites in human postmortem brains showed consistent significant reductions in the density of sigma, but not PCP sites, in schizophrenics as compared with age-matched and postmortem interval-matched normal and suicide controls. Reductions in the density of sigma binding sites in schizophrenia were most prominent in temporal cerebral cortex, and were accompanied by a small increase in affinity for the ligand [3H]haloperidol. These data provide the first evidence for alterations in sigma binding sites in schizophrenia, and suggest that selective sigma ligands may be useful in the treatment of the disorder.

A brief study of the selectivity of norbinaltorphimine, (-)-cyclofoxy, and (+)-cyclofoxy among opioid receptor subtypes in vitro

Norbinaltorphimine (nor-BNI) is a bifunctional reagent developed as a selective antagonist of the kappa opioid receptor. In this paper we examined the in vitro selectivity of nor-BNI, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY), and the enantiomer of cycloFOXY, among opioid receptor subtypes. Nor BNI exhibited the highest affinity for kappa binding sites labeled by 3H-U69593 (Ki = 1.8nM), and was 27- to 29-fold less potent at mu and delta binding sites. In contrast, cycloFOXY had the highest affinity for mu binding sites (Ki = 2.62 nM), and bound to kappa and delta binding sites with Ki's of 9.3 nM and 89 nM, respectively. The enantiomer of cycloFOXY, did not inhibit binding even at concentrations greater than 10 microM, validating in part the use of 18F-labeled (+)-cycloFOXY to estimate "non-specific binding" in positron emission tomography. Additionally, we report that (S,S)-U50 488 and (R.R)-U50 488 bind to kappa binding sites labeled by 3H-U69 593 with Ki's of 0.89 nM and 299 nM, respectively.