clozapine and Amphetamine-Related-Disorders

Chronic methamphetamine (METH) treatment induces behavioral sensitization in rodents. During this process, hyperactivation of the mesolimbic dopamine system plays a central role, and dopamine D2-like receptor-based antipsychotics are known to alleviate the behavioral hyperactivity. The atypical antipsychotic, clozapine (Clz), acts partially as a dopamine D4 receptor (D4R) antagonist and mitigates hyperdopaminergic drug addiction and/or comorbid psychotic symptoms; however, it remains unclear whether D4R blockade contributes to the therapeutic effects of Clz. Here, we evaluated the potential role of D4R in regulating hyperdopaminergia-induced behavioral hyperactivity in METH behavioral sensitization and dopamine transporter (DAT) knockdown (KD) mice. Clz or a D4R-selective antagonist, L-745,870, were co-administered to mice with daily METH in a METH sensitization model, and Clz or L-745,870 were administered alone in a DAT KD hyperactivity model. Locomotor activity and accumbal D4R expression were analyzed. Clz suppressed both the initiation and expression of METH behavioral sensitization, as well as DAT KD hyperactivity. However, repetitive Clz treatment induced tolerance to the suppression effect on METH sensitization initiation. In contrast, D4R inhibition by L-745,870 had no effect on METH sensitization or DAT KD hyperactivity. Accumbal D4R expression was similar between METH-sensitized mice with and without Clz co-treatment. In sum, our results suggest the mesolimbic D4R does not participate in behavioral sensitization encoded by hyperdopaminergia, a finding which likely extends to the therapeutic effects of Clz. Therefore, molecular targets other than D4R should be prioritized in the development of future therapeutics for treatment of hyperdopaminergia-dependent neuropsychiatric disorders.

Topics: Amphetamine-Related Disorders; Animals; Antipsychotic Agents; Behavior, Animal; Central Nervous System Sensitization; Clozapine; Disease Models, Animal; Dopamine Agents; Locomotion; Methamphetamine; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Mice, Knockout; Mice, Transgenic; Psychotic Disorders; Pyridines; Pyrroles; Receptors, Dopamine D4

Our report of a patient with severe tardive dyskinesia (TD) who has been exposed to both typical antipsychotic and clozapine, olanzapine and quetiapine during a 124-week follow-up period supports the possible beneficial effect of atypical antipsychotics on pre-existing symptoms of TD. Persistently high AIMS scores during all the periods of treatment with typical antipsychotics contrast strongly with the drop in scores that occurs in strict chronological sequence after switching to both clozapine (45%), olanzapine (27.8%) and quetiapine (85%). Since the reversal to haloperidol from the three atypical agents was systemically associated with a return to high AIMS scores, it seems likely that the improvement noted with clozapine, olanzapine and quetiapine represents a temporary symptomatic effect rather than a sustained resolution of the disorder. The olanzapine-clozapine-quetiapine rank order of increasing effectiveness against TD symptoms suggests that this property, although shared by the atypical antipsychotics, is to some degree drug-specific. Patient- and/or drug-dependent mechanisms may be involved in this gradient of effect.

Topics: Amphetamine-Related Disorders; Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dyskinesia, Drug-Induced; Female; Haloperidol; Humans; Male; Olanzapine; Quetiapine Fumarate; Schizophrenia, Paranoid