Time-dependent effects of haloperidol on glutamine and GABA homeostasis and astrocyte activity in the rat brain

Effects of gestational haloperidol exposure on mRNA expressions related to glutamate and GABA receptors in offspring

Antipsychotic treatment is vital for patients with schizophrenia even in the perinatal period, but the impact at the molecular biological level on offspring is unclear. The aim of the present study was to investigate the effects of intraperitoneal haloperidol injection to pregnant mice on glutamate and GABA receptors in the brain of offspring mice. Eight-week-old pregnant mice were treated with either intraperitoneal haloperidol or normal saline injection, and their offspring were defined as F1 mice. In addition, eight-week-old male mice were used as acute mice that were intraperitoneally injected with haloperidol or normal saline for 20 days. mRNA expression levels were measured by RT-qPCR. Western blotting was performed of the frontal lobes of F1 mice. In the hippocampi of F1 mice, Grik3 (p = 0.023) and Gabra3 (p = 0.004) mRNA expression levels were significantly higher in the haloperidol group than in the control group, whereas Gria2 (p < 0.001) and Grin2a (p < 0.001) mRNA expression levels were significantly lower in the haloperidol group than in the control group. Gria2 (p = 0.015), and Grik3 (p = 0.037), and Grin2a (p = 0.012) mRNA expression levels were significantly lower in the haloperidol group than in the control group in the frontal lobes of F1 mice. In the hippocampi of acute mice, Grik3 (p = 0.049) and Gabra3 (p = 0.007) mRNA expression levels were significantly decreased in the haloperidol group. Fetal exposure to haloperidol can affect glutamate and GABA receptors through mRNA expression changes in the brain of offspring.

Stuttering: A Disorder of Energy Supply to Neurons?

Stuttering is a disorder characterized by intermittent loss of volitional control of speech movements. This hypothesis and theory article focuses on the proposal that stuttering may be related to an impairment of the energy supply to neurons. Findings from electroencephalography (EEG), brain imaging, genetics, and biochemistry are reviewed: (1) Analyses of the EEG spectra at rest have repeatedly reported reduced power in the beta band, which is compatible with indications of reduced metabolism. (2) Studies of the absolute level of regional cerebral blood flow (rCBF) show conflicting findings, with two studies reporting reduced rCBF in the frontal lobe, and two studies, based on a different method, reporting no group differences. This contradiction has not yet been resolved. (3) The pattern of reduction in the studies reporting reduced rCBF corresponds to the regional pattern of the glycolytic index (GI; Vaishnavi et al., 2010). High regional GI indicates high reliance on non-oxidative metabolism, i.e., glycolysis. (4) Variants of the gene ARNT2 have been associated with stuttering. This gene is primarily expressed in the brain, with a pattern roughly corresponding to the pattern of regional GI. A central function of the ARNT2 protein is to act as one part of a sensor system indicating low levels of oxygen in brain tissue and to activate appropriate responses, including activation of glycolysis. (5) It has been established that genes related to the functions of the lysosomes are implicated in some cases of stuttering. It is possible that these gene variants result in a reduced peak rate of energy supply to neurons. (6) Lastly, there are indications of interactions between the metabolic system and the dopamine system: for example, it is known that acute hypoxia results in an elevated tonic level of dopamine in the synapses. Will mild chronic limitations of energy supply also result in elevated levels of dopamine? The indications of such interaction effects suggest that the metabolic theory of stuttering should be explored in parallel with the exploration of the dopaminergic theory.

Investigation of Risperidone Treatment Associated With Enhanced Brain Activity in Patients Who Stutter

Stuttering is a childhood onset fluency disorder that leads to impairment in speech. A randomized, double-blinded placebo-controlled study was conducted with 10 adult subjects to observe the effects of risperidone (a dopamine receptor 2/serotonin receptor 2 antagonist) on brain metabolism, using [¹⁸F] deoxyglucose as the marker. At baseline and after 6 weeks of taking risperidone (0.5–2.0 mg/day) or a placebo pill, participants were assigned to a solo reading aloud task for 30 min and subsequently underwent a 90-min positron emission tomography scan. Paired t-tests were performed to compare the pre-treatment vs. post-treatment in groups. After imaging and analysis, the blind was broken, which revealed an equal number of subjects of those on risperidone and those on placebo. There were no significant differences in the baseline scans taken before medication randomization. However, scans taken after active treatment demonstrated higher glucose uptake in the specific regions of the brain for those in the risperidone treatment group (p < 0.05). Risperidone treatment was associated with increased metabolism in the left striatum, which consists of the caudate and putamen, and the Broca’s area. The current study strengthens previous research that suggests the role of elevated dopamine activity and striatal hypometabolism in stuttering. We propose that the mechanism of risperidone’s action in stuttering, in part, involves increased metabolism of striatal astrocytes. We conclude that using neuroimaging techniques to visualize changes in the brain of those who stutter can provide valuable insights into the pathophysiology of the disorder and guide the development of future interventions.

Olanzapine-Induced Activation of Hypothalamic Astrocytes and Toll-Like Receptor-4 Signaling via Endoplasmic Reticulum Stress Were Related to Olanzapine-Induced Weight Gain

The antipsychotic drug olanzapine is associated with serious obesity side effects. Hypothalamic astrocytes and associated toll-like receptor-4 (TLR4) signaling play an essential role in obesity pathogenesis. This study investigated the effect of olanzapine on astrocytes and TLR4 signaling both in vitro and in the rat hypothalamus and their potential role in olanzapine-induced weight gain. We found that olanzapine treatment for 24 h dose-dependently increased cell viability, increased the protein expression of astrocyte markers including glial fibrillary acidic protein (GFAP) and S100 calcium binding protein B (S100B), and activated TLR4 signaling in vitro. In rats, 8- and 36-day olanzapine treatment caused weight gain accompanied by increased GFAP and S100B protein expression and activated TLR4 signaling in the hypothalamus. These effects still existed in pair-fed rats, suggesting that these effects were not secondary effects of olanzapine-induced hyperphagia. Moreover, treatment with an endoplasmic reticulum (ER) stress inhibitor, 4-phenylbutyrate, inhibited olanzapine-induced weight gain and ameliorated olanzapine-induced changes in hypothalamic GFAP, S100B, and TLR4 signaling. The expression of GFAP, S100B, and TLR4 correlated with food intake and weight gain. These findings suggested that olanzapine-induced increase in hypothalamic astrocytes and activation of TLR4 signaling were related to ER stress, and these effects may be related to olanzapine-induced obesity.

Effects of Antipsychotic Drugs: Cross Talk Between the Nervous and Innate Immune System

Converging lines of evidence suggest that activation of microglia (innate immune cells in the central nervous system [CNS]) is present in a subset of patients with schizophrenia. The extent to which antipsychotic drug treatment contributes to or combats this effect remains unclear. To address this question, we reviewed the literature for evidence that antipsychotic exposure influences brain microglia as indexed by in vivo neuroimaging and post-mortem studies in patients with schizophrenia and experimental animal models. We found no clear evidence from clinical studies for an effect of antipsychotics on either translocator protein (TSPO) radioligand binding (an in vivo neuroimaging measure of putative gliosis) or markers of brain microglia in post-mortem studies. In experimental animals, where drug and illness effects may be differentiated, we also found no clear evidence for consistent effects of antipsychotic drugs on TSPO radioligand binding. By contrast, we found evidence that chronic antipsychotic exposure may influence central microglia density and morphology. However, these effects were dependent on the dose and duration of drug exposure and whether an immune stimulus was present or not. In the latter case, antipsychotics were generally reported to suppress expression of inflammatory cytokines and inducible inflammatory enzymes such as cyclooxygenase and microglia activation. No clear conclusions could be drawn with regard to any effect of antipsychotics on brain microglia from current clinical data. There is evidence to suggest that antipsychotic drugs influence brain microglia in experimental animals, including possible anti-inflammatory actions. However, we lack detailed information on how these drugs influence brain microglia function at the molecular level. The clinical relevance of the animal data with regard to beneficial treatment effects and detrimental side effects of antipsychotic drugs also remains unknown, and further studies are warranted.

Ca2+ signaling as a mechanism of haloperidol-induced cytotoxicity in human astrocytes and assessing the protective role of a Ca2+ chelator

Haloperidol, a typical antipsychotic medication, has been shown to possess various biological effects in different brain models. However, the impact of haloperidol on Ca²⁺ signaling in astrocytes is elusive. This study explored the effect of haloperidol on cytosolic free Ca²⁺ levels ([Ca²⁺]_i) and viability, and established these two connections in Gibco® Human Astrocytes (GHAs) and DI TNC1 rat astrocytes. Haloperidol (5-20 μM) caused [Ca²⁺]_i rises in a concentration-dependent manner in GHAs but not in DI TNC1 cells. Furthermore, removal of extracellular Ca²⁺ reduced haloperidol's effect by approximately 30% in GHAs. Haloperidol (20-40 μM) evoked concentration-dependent cytotoxicity in GHAs and DI TNC1 cells. However, chelating cytosolic Ca²⁺ with the Ca²⁺ chelator BAPTA/AM significantly reversed haloperidol's cytotoxicity only in GHAs. In GHAs, haloperidol-induced Ca²⁺ entry was inhibited by store-operated Ca²⁺ modulators (2-APB and SKF96365) and the protein kinase C (PKC) inhibitor GF109203X. This Ca²⁺ entry induced by haloperidol was confirmed by Mn²⁺ entry-induced quench of fura-2 fluorescence. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished haloperidol-induced [Ca²⁺]_i rises. Conversely, treatment with haloperidol inhibited 45% of BHQ-evoked [Ca²⁺]_i rises. Moreover, haloperidol-induced Ca²⁺ release from the endoplasmic reticulum was abolished by inhibition of phospholipase C (PLC) by U73122. Together, in GHAs but not in DI TNC1 cells, haloperidol caused Ca²⁺-associated cell death, induced Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels, and evoked PLC-dependent Ca²⁺ release from the endoplasmic reticulum. The protective effect of Ca²⁺ chelating on haloperidol-induced cytotoxicity in human astrocytes was also demonstrated.

Alterations in glutamatergic signaling in the brain of dopamine supersensitivity psychosis and non-supersensitivity psychosis model rats

BACKGROUND

The long-term administration of antipsychotics is known to induce dopamine supersensitivity psychosis (DSP). Although the mechanism of DSP involves mainly a compensatory upregulation of dopamine D2 receptors, the precise mechanisms underlying DSP are unknown. It is known that glutamatergic signaling plays a key role in psychosis. We thus conducted this study to investigate whether glutamatergic signaling plays a role in the development of DSP.

METHODS

Haloperidol (0.75 mg/kg/day for 14 days) or vehicle was administered to rats via osmotic mini-pump. Haloperidol-treated rats were divided into groups of DSP rats and non-DSP rats based on locomotion data. Tissue levels of glutamate, glutamine, glycine, L-serine, D-serine, and GABA and the protein expressions of N-methyl-D-aspartate receptors (NMDAR), glutamic acid decarboxylase (GAD), and serine hydroxymethyltransferase (SHMT) in the rat brain regions were examined.

RESULTS

In the DSP rats, the ratio of GABA to glutamate was significantly increased. In addition, the ratio of L-serine to glycine was increased. The striatal expressions of GAD and SHMT2 in the DSP rats were significantly increased. In contrast, the striatal expression of NMDAR2B in the non-DSP rats was significantly decreased.

CONCLUSIONS

The present study suggests that glutamatergic signaling is relatively decreased to GABA in DSP rats. Our results also showed that excessive doses of haloperidol can induce striatal NMDAR hypofunction in non-DSP rats, which could prevent the formation of tardive dyskinesia but cause treatment resistance. In view of the need for therapeutic strategies for treatment-resistant schizophrenia, further research exploring our present findings is necessary.

Reduced cortical volume and elevated astrocyte density in rats chronically treated with antipsychotic drugs-linking magnetic resonance imaging findings to cellular pathology

BACKGROUND

Increasing evidence suggests that antipsychotic drugs (APD) might affect brain structure directly, particularly the cerebral cortex. However, the precise anatomical loci of these effects and their underlying cellular basis remain unclear.

METHODS

With ex vivo magnetic resonance imaging in rats treated chronically with APDs, we used automated analysis techniques to map the regions that show maximal impact of chronic (8 weeks) treatment with either haloperidol or olanzapine on the rat cortex. Guided by these imaging findings, we undertook a focused postmortem investigation with stereology.

RESULTS

We identified decreases in the volume and thickness of the anterior cingulate cortex (ACC) after chronic APD treatment, regardless of the APD administered. Postmortem analysis confirmed these volumetric findings and demonstrated that chronic APD treatment had no effect on the total number of neurons or S100β+ astrocytes in the ACC. In contrast, an increase in the density of these cells was observed.

CONCLUSIONS

This study demonstrates region-specific structural effects of chronic APD treatment on the rat cortex, primarily but not exclusively localized to the ACC. At least in the rat, these changes are not due to a loss of either neurons or astrocytes and are likely to reflect a loss of neuropil. Although caution needs to be exerted when extrapolating results from animals to patients, this study highlights the power of this approach to link magnetic resonance imaging findings to their histopathological origins.

Metabolic Dysfunction of Astrocyte: An Initiating Factor in Beta-amyloid Pathology?

Astrocytes, the most important energy regulator in the brain, support brain energy needs. In the meantime, numerous studies have demonstrated that impaired brain glucose metabolism is closely linked to abnormal astrocytic metabolism in AD. Indeed, the interaction between amyloid plaques and perturbed astrocytic homeostasis contributes to AD pathogenesis and astrocytic metabolic dysfunction is thought to be a trigger for Aβ pathology through oxidative stress and neuroinflammation Moreover, astrocytic metabolic dysfunction may regulate Aβ generation via modulating proteolytic processing of amyloid precursor protein (APP) by β-secretase, γ-secretase, and α-secretase, and may also modulate APP post-translational modifications such as glycosylation, phosphorylation, and tyrosine sulfation. While it is known that metabolic dysfunction of astrocytes contributes to the failure of Aβ clearance, it has also been reported that such dysfunction has neuroprotective property and exhibits no detrimental outcomes. Therefore, the exact role of astrocytic metabolic dysfunction in Aβ pathology remains to be further investigated.