l-745870 and Schizophrenia

Topics: Animals; Antipsychotic Agents; Cholinergic Agonists; Disease Models, Animal; Dopamine Antagonists; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Humans; Mice; Mice, Transgenic; Nitric Oxide Synthase; Receptor, Serotonin, 5-HT2A; Receptors, AMPA; Receptors, Dopamine D2; Receptors, Dopamine D4; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotensin; Receptors, Serotonin; Schizophrenia; Serotonin Antagonists

The discovery of a novel high-affinity and selective dopamine D4 receptor antagonist, L-745,870, and the results of clinical trials with this compound are reviewed. Despite several lines of evidence which suggest that a selective D4 receptor antagonist may be an effective antipsychotic agent with a lower propensity to induce extrapyramidal side-effects, L-745,870 was ineffective as an antipsychotic in humans.

Topics: Animals; Antipsychotic Agents; Biological Availability; Clinical Trials as Topic; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Humans; Pyridines; Pyrroles; Receptors, Dopamine D4; Rodentia; Schizophrenia

Several atypical antipsychotic drugs (APDs) have high affinity for the dopamine (DA) D

Topics: Animals; Antipsychotic Agents; Benzamides; Clozapine; Cognitive Dysfunction; Female; Lurasidone Hydrochloride; Phencyclidine; Piperazines; Pyridines; Pyrroles; Rats; Rats, Long-Evans; Receptor, Serotonin, 5-HT1A; Receptors, Dopamine D4; Schizophrenia; Serotonin 5-HT1 Receptor Agonists

Previous studies have shown D2-like dopamine receptor involvement in the regulation of phospholipid methylation (PLM), while others have documented impaired methionine and folate metabolism in schizophrenia. Utilizing [14C]formate labeling in cultured neuroblastoma cell lines, we now show that D4 dopamine receptors (D4R) mediate the stimulatory effect of dopamine (DA) on PLM. The effect of DA was potently blocked by highly D4R-selective antagonists and stimulated by the D4R-selective agonist CP-226269. DA-stimulated PLM was dependent upon the activity of methionine cycle enzymes, but DA failed to increase PLM in [3H]methionine labeling studies, indicating that a methionine residue in the D4R might be involved in mediating PLM. A direct role for MET313, located on transmembrane helix No. 6 immediately adjacent to phospholipid headgroups, was further suggested from adenosylation, site-directed mutagenesis and GTP-binding results. A comparison of PLM in lymphocytes from schizophrenia patients vs control samples showed a four-fold lower activity in the schizophrenia group. These findings reveal a novel mechanism by which the D4R can regulate membrane composition. Abnormalities in D4R-mediated PLM may be important in psychiatric illnesses such as schizophrenia.

Topics: Amino Acid Sequence; Aminopyridines; Animals; Benzazepines; Binding Sites; Carbon Radioisotopes; CHO Cells; Clozapine; Cricetinae; Dopamine Agonists; Dopamine Antagonists; Dopamine D2 Receptor Antagonists; Formates; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Methionine; Mutagenesis, Site-Directed; Neuroblastoma; Phospholipids; Phosphorylation; Piperidines; Psychotic Disorders; Pyridines; Pyrroles; Raclopride; Receptors, Dopamine D2; Receptors, Dopamine D4; Recombinant Proteins; S-Adenosylmethionine; Salicylamides; Schizophrenia; Transfection; Tumor Cells, Cultured