Mechanism of action of clozapine-induced modification of motor behavior in an animal model of the "super-off" phenomenon

Clozapine-induced cardiotoxicity in rats: Involvement of tumour necrosis factor alpha, NF-κβ and caspase-3

Clozapine, an ideal antipsychotic drug for the treatment of resistant schizophrenia, is considered the most underutilised treatment for schizophrenia. However, safety concerns have been raised about clozapine-induced cardiotoxicity, which may lead to sudden death, particularly in young patients. The exact mechanism of clozapine cardiotoxicity has not yet been thoroughly studied. This study aimed to investigate the possible mechanisms of clozapine-induced cardiotoxicity in a rat model. Young male Wistar rats were treated with clozapine (10, 15 and 25 mg/kg/day, i.p.) for 21 days. Haemodynamic and echocardiographic studies were performed for assessment of cardiac functions. Heart sections were studied histopathologically and immunohistochemically. Serum and cardiac markers of cardiotoxicity, oxidative stress, inflammation and apoptosis were evaluated. Heart sections of CLZ-treated animals showed increased cardiac inflammation that correlated with the clozapine dose. Serum levels of CK-MB and LDH levels increased, as did cardiac levels of TNF-α, MDA, NO, myeloperoxidase (MPO), 8-OHdG, caspase-3 and NF-κB p65. In contrast, GSH levels and GSH-Px activity decreased. Furthermore, immunohistochemical examination of the heart sections showed positive immunostaining for both 3-nitrotyrosine and caspase-3 in all clozapine-treated groups. Clozapine, particularly in relatively high doses, has a clear cardiotoxic effect. This cardiotoxicity is accompanied by increased myocardial oxidative stress, inflammatory cytokines, DNA damage and apoptosis with attenuation in antioxidant defences, thus explaining the previously reported myocarditis and pericarditis during clozapine therapy in clinical studies.

The serotonergic system in Parkinson's disease

Although the cardinal manifestations of Parkinson's disease (PD) are attributed to a decline in dopamine levels in the striatum, a breadth of non-motor features and treatment-related complications in which the serotonergic system plays a pivotal role are increasingly recognised. Serotonin (5-HT)-mediated neurotransmission is altered in PD and the roles of the different 5-HT receptor subtypes in disease manifestations have been investigated. The aims of this article are to summarise and discuss all published preclinical and clinical studies that have investigated the serotonergic system in PD and related animal models, in order to recapitulate the state of the current knowledge and to identify areas that need further research and understanding.