Typical and atypical antipsychotic drugs target dopamine and cyclic AMP-regulated phosphoprotein, 32 kDa and neurotensin-containing neurons, but not GABAergic interneurons in the shell of nucleus accumbens of ventral striatum

ACE activity in blood and brain axis in an animal model for schizophrenia: Effects of dopaminergic manipulation with antipsychotics and psychostimulants

Objectives: Angiotensin I-converting enzyme (ACE) was initially correlated with schizophrenia (SCZ) in studies showing a correlation of ACE increased enzyme activity with memory impairments. Possible role for ACE in SCZ was also suggested by ACE activity interaction with dopaminergic mechanisms to modulate abnormalities of sensorimotor gating. In addition, we have demonstrated higher ACE activity in blood of SCZ subjects, its implication in cognitive performance in SCZ and its power as a predictor for SCZ diagnosis.Methods: ACE activity was determined in the serum and in selected brain regions of an animal model presenting SCZ-like behaviour, before and after the treatment with typical and atypical antipsychotics, and also in the serum of animals receiving the psychostimulants amphetamine/lisdexamphetamine.Results: Dopaminergic manipulations with antipsychotics and psychostimulants influenced the ACE activity, but with no correlation with the animal blood pressure.Conclusions: The validity of measuring ACE activity in animal blood to predict activity in the CNS, as well as the lack of correlation between the activity and blood pressure, before and after the treatment with antipsychotics, were confirmed here. Correlations of the present findings with data from clinical studies also strengthen the value of this animal model for studying several aspects of SCZ.

Impact of nuclear distribution element genes in the typical and atypical antipsychotics effects on nematode Caenorhabditis elegans: Putative animal model for studying the pathways correlated to schizophrenia

The nuclear distribution element genes are conserved from fungus to humans. The nematode Caenorhabditis elegans expresses two isoforms of nuclear distribution element genes, namely nud-1 and nud-2. While nud-1 was functionally demonstrated to be the worm nudC ortholog, bioinformatic analysis revealed that the nud-2 gene encodes the worm ortholog of the mammalian NDE1 (Nuclear Distribution Element 1 or NudE) and NDEL1 (NDE-Like 1 or NudEL) genes, which share overlapping roles in brain development in mammals and also mediate the axon guidance in mammalian and C. elegans neurons. A significantly higher NDEL1 enzyme activity was shown in treatment non-resistant compared to treatment resistant SCZ patients, who essentially present response to the therapy with atypical clozapine but not with typical antipsychotics. Using C. elegans as a model, we tested the consequence of nud genes suppression in the effects of typical and atypical antipsychotics. To assess the role of nud genes and antipsychotic drugs over C. elegans behavior, we measured body bend frequency, egg laying and pharyngeal pumping, which traits are controlled by specific neurons and neurotransmitters known to be involved in SCZ, as dopamine and serotonin. Evaluation of metabolic and behavioral response to the pharmacotherapy with these antipsychotics demonstrates an important unbalance in serotonin pathway in both nud-1 and nud-2 knockout worms, with more significant effects for nud-2 knockout. The present data also show an interesting trend of mutant knockout worm strains to present a metabolic profile closer to that observed for the wild-type animals after the treatment with the typical antipsychotic haloperidol, but which was not observed for the treatment with the atypical antipsychotic clozapine. Paradoxically, behavioral assays showed more evident effects for clozapine than for haloperidol, which is in line with previous studies with rodent animal models and clinical evaluations with SCZ patients. In addition, the validity and reliability of using this experimental animal model to further explore the convergence between the dopamine/serotonin pathways and neurodevelopmental processes was demonstrated here, and the potential usefulness of this model for evaluating the metabolic consequences of treatments with antipsychotics is also suggested.

The effect of clozapine on the AMPK-ACC-CPT1 pathway in the rat frontal cortex

Clozapine is an antipsychotic drug that has a greater efficacy than other medications in some contexts, especially for the treatment of treatment-resistant schizophrenia. However, clozapine induces more metabolic side-effects involving abnormality in lipid metabolism compared to other antipsychotics. AMP-activated protein kinase (AMPK) plays a central role in controlling lipid metabolism through modulating the downstream acetyl CoA carboxylase (ACC) and carnitine palmitoyl transferase 1 (CPT1) pathway. In this study, we investigated the effect of a single intraperitoneal injection of clozapine on the AMPK-ACC-CPT1 pathway in the rat frontal cortex, which has been implicated as a target site for this antipsychotic drug. At 2 h after injection, the clinically relevant dose of clozapine had activated AMPK, with increased phosphorylation of AMPKα at Thr(172), and had inactivated ACC, with increased phosphorylation of ACC at Ser(79). In addition, clozapine activated the brain-specific isoform of CPT1, CPT1c, whose activity is inhibited by unphosphorylated ACC, in the rat frontal cortex. Immunohistochemistry and immunofluorescence analysis showed that clozapine induced an increase in number of p-AMPKα (Thr(172))- and p-ACC (Ser(79))-positive cells among the neurons of the rat frontal cortex. Taken together, these results show that clozapine activated the AMPK-ACC-CPT1 pathway in the neurons of the rat frontal cortex. These findings indicate that the antipsychotic agent clozapine affects the lipid regulatory system of neurons in the brain.

Effects of electroconvulsive shock on the phosphorylation of DARPP-32 in rat striatum

Dopamine- and cAMP-regulated phosphoprotein with molecular weight 32 kDa (DARPP-32) is a key integrative molecule in the dopaminergic and glutamatergic signaling pathways in the striatum. Electroconvulsive shock (ECS), which induces massive neuronal depolarization, can activate various signaling pathways. In this study we investigated whether ECS could affect the phosphorylation status of DARPP-32. Male Sprague-Dawley rats underwent ECS and were sacrificed by decapitation at 0, 2, 10, 60, and 180 min after treatment. The phosphorylations of Thr34 and Thr75 residues of DARPP-32 and Ser159 residue of cyclin-dependent kinase 5 (CDK5) were investigated in the striatum. The activity of protein phosphatase 1 (PP1) and the binding between DARPP-32 and PP1 were also analyzed. Thr34 phosphorylation of DARPP-32 increased immediately after ECS and this state was maintained for more than 60 min. The activity of PP1 decreased and the binding between PP1 and DARPP-32 increased in accordance with this phosphorylation pattern. However, the phosphorylation at Thr75 showed no significant change except for an initial transient decrease. The phosphorylation of CDK5, which is responsible for Thr75 phosphorylation of DARPP-32, did not exhibit significant fluctuations. Our findings indicate that ECS increases Thr34 phosphorylation of DARPP-32, and thus inhibits the activity of PP1.