Baseline temperature in an animal model of schizophrenia: long-term effects of perinatal phencyclidine administration

Effects of Antipsychotics on the Hypothalamus-Pituitary-Adrenal Axis in a Phencyclidine Animal Model of Schizophrenia

Schizophrenia (SCH) is a mental disorder that requires long-term antipsychotic treatment. SCH patients are thought to have an increased sensitivity to stress. The dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, observed in SCH, could include altered levels of glucocorticoids, glucocorticoid receptors (GRs), and associated proteins. The perinatal administration of phencyclidine (PCP) to rodents represents an animal model of SCH. This study investigated the effects of perinatal PCP exposure and subsequent haloperidol/clozapine treatment on corticosterone levels measured by ELISA and the expression of GR-related proteins (GR, pGR, HSP70, HSP90, FKBP51, and 11β-Hydroxysteroid dehydrogenase-11β-HSD) determined by Western blot, in different brain regions of adult rats. Six groups of male rats were treated on the 2nd, 6th, 9th, and 12th postnatal days (PN), with either PCP or saline. Subsequently, one saline and one PCP group received haloperidol/clozapine from PN day 35 to PN day 100. The results showed altered GR sensitivity in the rat brain after PCP exposure, which decreased after haloperidol/clozapine treatment. These findings highlight disturbances in the HPA axis in a PCP-induced model of SCH and the potential protective effects of antipsychotics. To the best of our knowledge, this is the first study to investigate the effects of antipsychotic drugs on the HPA axis in a PCP animal model of SCH.

The effect of phencyclidine-mediated blockade of NMDA receptors in the early postnatal period on glutathione and sulfur amino acid levels in the rat brain as a potential causative factor of schizophrenia-like behavior in adulthood

BACKGROUND

Phencyclidine, an NMDA receptor antagonist, is frequently used to model behavioral and neurochemical changes correlated with schizophrenia in laboratory animals. The present study aimed to examine the effects of repeated administration of phencyclidine during early postnatal development on the contents of glutathione and sulfur-containing amino acids, as well as the activity of antioxidant enzymes in the brain of 12-day-old rats, and schizophrenia-like symptoms in adulthood.

METHODS

Male Sprague-Dawley pups were administered phencyclidine (10 mg/kg) or saline subcutaneously on the postnatal days p2, p6, p9 and p12. In 12-day-old pups, 4 h after the last dose of phencyclidine, the levels of glutathione, cysteine, methionine, and homocysteine, and the enzymatic activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) were measured in the frontal cortex, hippocampus, and striatum. In 70-72-day-old rats, schizophrenia-like symptoms were assessed using behavioral tests.

RESULTS

Biochemical data showed that perinatal phencyclidine treatment significantly reduced glutathione and cysteine levels in all brain structures studied, methionine was diminished in the striatum, and homocysteine in both the frontal cortex and striatum. GR activity was increased in the frontal cortex while SODactivity was decreased in the hippocampus. Behaviorally, perinatal phencyclidine induced long-term deficits in social and cognitive function and a decrease in locomotor activity assessed as the time of walking. Finally, perinatal treatment with phencyclidine resulted in a significant reduction in body weight gain over time.

CONCLUSION

Our research provides further evidence for the usefulness of the phencyclidine-induced neurodevelopmental model of schizophrenia for studying the pathogenesis of schizophrenia.

Neonatal NMDA blockade alters the LTP, LTD and cognitive functions in male and female Wistar rats

There is compelling evidence that neonatal blockade of NMDA receptors by phencyclidine (PCP) is associated with cognitive impairment in adulthood but little is known about the effects of early life PCP treatment on synaptic function later in life. Here, we sought to determine whether early life exposure to PCP alters the electrophysiologic function of hippocampal CA1 neurons in adult rats. To this end, male and female Wistar rats received either saline or PCP (10 mg/kg) on postnatal days (PND) 7, 9, and 11, and then underwent separate behavioral and electrophysiology tests in adulthood. Neonatal PCP treatment did not alter basic synaptic transmission and had only a modest effect on frequency following (FF) capacity but significantly decreased the paired-pulse facilitation (PPF) in the Schaffer collateral (SC)-CA1 pathway. We found that PCP treatment significantly attenuated the long-term potentiation (LTP) and long-term depression (LTD) in CA1 neurons accompanied by pronounced alteration in complex response profile in adult rats. The electrophysiology data were comparable in male and female rats and reliably associated with impaired spatial reference and working memories in these animals. Overall, this study suggests that blockade of NMDA receptors during early life deteriorates the short-term and long-term synaptic plasticity and complex response profile of CA1 neurons in adulthood.

A Potential Interface between the Kynurenine Pathway and Autonomic Imbalance in Schizophrenia

Schizophrenia is a neuropsychiatric disorder characterized by various symptoms including autonomic imbalance. These disturbances involve almost all autonomic functions and might contribute to poor medication compliance, worsened quality of life and increased mortality. Therefore, it has a great importance to find a potential therapeutic solution to improve the autonomic disturbances. The altered level of kynurenines (e.g., kynurenic acid), as tryptophan metabolites, is almost the most consistently found biochemical abnormality in schizophrenia. Kynurenic acid influences different types of receptors, most of them involved in the pathophysiology of schizophrenia. Only few data suggest that kynurenines might have effects on multiple autonomic functions. Publications so far have discussed the implication of kynurenines and the alteration of the autonomic nervous system in schizophrenia independently from each other. Thus, the coupling between them has not yet been addressed in schizophrenia, although their direct common points, potential interfaces indicate the consideration of their interaction. The present review gathers autonomic disturbances, the impaired kynurenine pathway in schizophrenia, and the effects of kynurenine pathway on autonomic functions. In the last part of the review, the potential interaction between the two systems in schizophrenia, and the possible therapeutic options are discussed.

Perinatal administration of phencyclidine alters expression of Lingo-1 signaling pathway proteins in the prefrontal cortex of juvenile and adult rats

Postnatal administration of phencyclidine (PCP) in rodents causes major brain dysfunction leading to severe disturbances in behavior lasting into adulthood. This model is routinely employed to model psychiatric disorders such as schizophrenia, as it reflects schizophrenia-related brain disturbances including increased apoptosis, and disruptions to myelin and plasticity processes. Leucine-rich repeat and Immunoglobin-like domain-containing protein 1 (Lingo-1) is a potent negative regulator of both axonal myelination and neurite extension. The Nogo receptor (NgR)/tumor necrosis factor (TNF) receptor orphan Y (TROY) and/or p75 neurotrophin receptor (p75) complex, with no lysine (K) (WNK1) and myelin transcription factor 1 (Myt1) are co-receptors or cofactors in Lingo-1 signaling pathways in the brain. We have examined the developmental trajectory of these proteins in a neurodevelopmental model of schizophrenia using PCP to determine if Lingo-1 pathways are altered in the prefrontal cortex throughout different stages of life. Sprague-Dawley rats were injected with PCP (10 mg/kg) or saline on postnatal days (PN)7, 9, and 11 and killed at PN12, 5 or 14 weeks for measurement of Lingo-1 signaling proteins in the prefrontal cortex. Myt1 was decreased by PCP at PN12 (P=0.045), and at 14 weeks PCP increased Lingo-1 (P=0.037), TROY (P=0.017), and WNK1 (P=0.003) expression. This is the first study reporting an alteration in Lingo-1 signaling proteins in the rat prefrontal cortex both directly after PCP treatment in early development and in adulthood. We propose that Lingo-1 pathways may be negatively regulating myelination and neurite outgrowth following the administration of PCP, and that this may have implications for the cortical dysfunction observed in schizophrenia.

Journey to the Center of the Fetal Brain: Environmental Exposures and Autophagy

Fetal brain development is known to be affected by adverse environmental exposures during pregnancy, including infection, inflammation, hypoxia, alcohol, starvation, and toxins. These exposures are thought to alter autophagy activity in the fetal brain, leading to adverse perinatal outcomes, such as cognitive and sensorimotor deficits. This review introduces the physiologic autophagy pathways in the fetal brain. Next, methods to detect and monitor fetal brain autophagy activity are outlined. An additional discussion explores possible mechanisms by which environmental exposures during pregnancy alter fetal brain autophagy activity. In the final section, a correlation of fetal autophagy activity with the observed postnatal phenotype is attempted. Our main purpose is to provide the current understanding or a lack thereof mechanisms on autophagy, underlying the fetal brain injury exposed to environmental insults.

Haloperidol affects bones while clozapine alters metabolic parameters - sex specific effects in rats perinatally treated with phencyclidine

Background

The presentation of schizophrenia (SCH) symptoms differs between the sexes. Long-term treatment with antipsychotics is frequently associated with decreased bone mineral density, increased fracture risk and metabolic side effects. Perinatal phencyclidine (PCP) administration to rodents represents an animal model of SCH. The aim of this study was to assess the effects of chronic haloperidol and clozapine treatment on bone mass, body composition, corticosterone, IL-6 and TNF-α concentrations and metabolic parameters in male and female rats perinatally treated with PCP.

Methods

Six groups of male and six groups of female rats (n = 6-12 per group) were subcutaneously treated on 2nd, 6th, 9th and 12th postnatal day (PN), with either PCP (10 mg/kg) or saline. At PN35, one NaCl and PCP group (NaCl-H and PCP-H) started receiving haloperidol (1 mg/kg/day) and one NaCl and PCP group (NaCl-C and PCP-C) started receiving clozapine (20 mg/kg/day) dissolved in drinking water. The remaining NaCl and PCP groups received water. Dual X-ray absorptiometry measurements were performed on PN60 and PN98. Animals were sacrificed on PN100. Femur was analysed by light microscopy. Concentrations of corticosterone, TNF-α and IL-6 were measured in serum samples using enzyme-linked immunosorbent assay (ELISA) commercially available kits. Glucose, cholesterol and triacylglycerol concentrations were measured in serum spectrophotometrically.

Results

Our results showed that perinatal PCP administration causes a significant decrease in bone mass and deterioration in bone quality in male and female rats. Haloperidol had deleterious, while clozapine had protective effect on bones. The effects of haloperidol on bones were more pronounced in male rats. It seems that the observed changes are not the consequence of the alterations of corticosterone, IL-6 and TNF-α concentration since no change of these factors was observed. Clozapine induced increase of body weight and retroperitoneal fat in male rats regardless of perinatal treatment. Furthermore, clozapine treatment caused sex specific increase in pro-inflammatory cytokines.

Conclusion

Taken together our findings confirm that antipsychotics have complex influence on bone and metabolism. Evaluation of potential markers for individual risk of antipsychotics induced adverse effects could be valuable for improvement of therapy of this life-long lasting disease.

Electronic supplementary material

The online version of this article (10.1186/s40360-017-0171-4) contains supplementary material, which is available to authorized users.

Alterations of ubiquitin related proteins in the pathology and development of schizophrenia: Evidence from human and animal studies

Gene expression analyses in post-mortem schizophrenia brains suggest that a number of ubiquitin proteasome system (UPS) genes are associated with schizophrenia; however the status of UPS proteins in the schizophrenia brain is largely unknown. Ubiquitin related proteins are inherently involved in memory, neuronal survival and morphology, which are processes implicated in neurodevelopmental disorders such as schizophrenia. We examined levels of five UPS proteins (Protein Inhibitor of Activated STAT2 [PIAS2], F-Box and Leucine rich repeat protein 21 [FBXL21], Mouse Double Minute 2 homolog [MDM2], Ubiquitin Carboxyl-Terminal Hydrolase-L1 [UCHL1] and Ubiquitin Conjugating Enzyme E2D1 [UBE2D1]) involved in these neuronal processes, within the dorsolateral prefrontal cortex of post-mortem schizophrenia subjects and matched controls (n = 30/group), in addition to across neurodevelopmental time-points (juvenile, adolescent and adult stages of life), utilizing a well-established neurodevelopmental phencyclidine (PCP) animal model of schizophrenia. We observed significant reductions in PIAS2, FBXL21 and MDM2 in schizophrenia subjects compared to controls (p-values ranging from 0.002 to 0.004). In our developmental PCP model, MDM2 protein was significantly reduced in adult PCP-treated rats compared to controls (p = 0.034). Additionally, FBXL21 (p = 0.022) and UCHL1 (p = 0.022) were significantly decreased, whilst UBE2D1 was increased (p = 0.022), in juvenile phencyclidine-treated rats compared to controls. This is the first study reporting alterations of UPS proteins in post-mortem human schizophrenia subjects and in a neurodevelopmental model of schizophrenia. The findings from this study provide strong support for a role of these UPS proteins in the pathology and development of schizophrenia.

N-Methyl D-Aspartate Receptor Antagonist Kynurenic Acid Affects Human Cortical Development

Kynurenic acid (KYNA), a neuroactive metabolite of tryptophan degradation, acts as an endogenous N-methyl-D-aspartate receptor (NMDAR) antagonist. Elevated levels of KYNA have been observed in pregnant women after viral infections and are considered to play a role in neurodevelopmental disorders. However, the consequences of KYNA-induced NMDAR blockade in human cortical development still remain elusive. To study the potential impact of KYNA on human neurodevelopment, we used an in vitro system of multipotent cortical progenitors, i.e., radial glia cells (RGCs), enriched from human cerebral cortex at mid-gestation (16–19 gestational weeks). KYNA treatment significantly decreased RGCs proliferation and survival by antagonizing NMDAR. This alteration resulted in a reduced number of cortical progenitors and neurons while number and activation of astrocytes increased. KYNA treatment reduced differentiation of RGCs into GABAergic neurons, while differentiation into glutamatergic neurons was relatively spared. Furthermore, in mixed cortical cultures KYNA triggered an inflammatory response as evidenced by increased levels of the pro-inflammatory cytokine IL-6. In conclusion, elevated levels of KYNA play a significant role in human RGC fate determination by antagonizing NMDARs and by activating an inflammatory response. The altered cell composition observed in cell culture following exposure to elevated KYNA levels suggests a mechanism for impairment of cortical circuitry formation in the fetal brain after viral infection, as seen in neurodevelopmental disorders such as schizophrenia.

Mitochondrial impairment, apoptosis and autophagy in a rat brain as immediate and long-term effects of perinatal phencyclidine treatment - influence of restraint stress

Phencyclidine (PCP) acts as a non-competitive antagonist of glutamatergic N-methyl-d-aspartate receptor. Its perinatal administration to rats causes pathophysiological changes that mimick some pathological features of schizophrenia (SCH). Numerous data indicate that abnormalities in mitochondrial structure and function could be associated with the development of SCH. Mitochondrial dysfunction could result in the activation of apoptosis and/or autophagy. The aim of this study was to assess immediate and long-term effects of perinatal PCP administration and acute restraint stress on the activity of respiratory chain enzymes, expression of apoptosis and autophagy markers and ultrastructural changes in the cortex and hippocampus of the rat brain. Six groups of rats were subcutaneously treated on 2nd, 6th, 9th and 12th postnatal days (P), with either PCP (10mg/kg) or saline (0.9% NaCl). One NaCl and one PCP group were sacrificed on P13, while other two NaCl and PCP groups were sacrificed on P70. The remaining two NaCl and PCP groups were subjected to 1h restraint stress prior sacrifice on P70. Activities of respiratory chain enzymes were assessed spectrophotometrically. Expression of caspase 3 and AIF as markers of apoptosis and Beclin 1, p62 and LC3, as autophagy markers, was assessed by Western blot. Morphological changes of cortical and hippocampal ultrastructure were determined by transmission electron microscopy. Immediate effects of perinatal PCP administration at P13 were increased activities of complex I in the hippocampus and cytochrome c oxidase (COX) in the cortex and hippocampus implying mitochondrial dysfunction. These changes were followed by increased expression of apoptotic markers. However the measurement of autophagy markers at this time point has revealed decrease of this process in cortex and the absence of changes in hippocampus. At P70 the activity of complex I was unchanged while COX activity was significantly decreased in cortex and increased in the hippocampus. Expressions of apoptotic markers were still significantly higher in PCP perinatally treated rats in all investigated structures, but the changes of autophagy markers have indicated increased level of autophagy also in both structures. Restraint stress on P70 has caused increase of COX activity both in NaCl and PCP perinatally treated rats, but this increase was lower in PCP group. Also, restraint stress resulted in decrease of apoptotic and increase of autophagy processes especially in the hippocampus of PCP perinatally treated group. The presence of apoptosis and autophagy in the brain was confirmed by transmission electron microscopy. In this study we have demonstrated for the first time the presence of autophagy in PCP model of SCH. Also, we have shown increased sensitivity of PCP perinatally treated rats to restraint stress, manifested in alterations of apoptotic and autophagy markers. The future studies are necessary to elucidate the role of mitochondria in the pathophysiology of SCH and putative significance for development of novel therapeutic strategies.

Abnormal Motor Activity and Thermoregulation in a Schizophrenia Rat Model for Translational Science

Background

Schizophrenia is accompanied by altered motor activity and abnormal thermoregulation; therefore, the presence of these symptoms can enhance the face validity of a schizophrenia animal model. The goal was to characterize these parameters in freely moving condition of a new substrain of rats showing several schizophrenia-related alterations.

Methods

Male Wistar rats were used: the new substrain housed individually (for four weeks) and treated subchronically with ketamine, and naive animals without any manipulations. Adult animals were implanted with E-Mitter transponders intraabdominally to record body temperature and locomotor activity continuously. The circadian rhythm of these parameters and the acute effects of changes in light conditions were analyzed under undisturbed circumstances, and the effects of different interventions (handling, bed changing or intraperitoneal vehicle injection) were also determined.

Results

Decreased motor activity with fragmented pattern was observed in the new substrain. However, these animals had higher body temperature during the active phase, and they showed wider range of its alterations, too. The changes in light conditions and different interventions produced blunted hyperactivity and altered body temperature responses in the new substrain. Poincaré plot analysis of body temperature revealed enhanced short- and long-term variabilities during the active phase compared to the inactive phase in both groups. Furthermore, the new substrain showed increased short- and long-term variabilities with lower degree of asymmetry suggesting autonomic dysregulation.

Conclusions

In summary, the new substrain with schizophrenia-related phenomena showed disturbed motor activity and thermoregulation suggesting that these objectively determined parameters can be biomarkers in translational research.

Perinatal phencyclidine administration decreases the density of cortical interneurons and increases the expression of neuregulin-1

RATIONALE

Perinatal phencyclidine (PCP) administration in rat blocks the N-methyl D-aspartate receptor (NMDAR) and causes symptoms reminiscent of schizophrenia in human. A growing body of evidence suggests that alterations in γ-aminobutyric acid (GABA) interneuron neurotransmission may be associated with schizophrenia. Neuregulin-1 (NRG-1) is a trophic factor important for neurodevelopment, synaptic plasticity, and wiring of GABA circuits.

OBJECTIVES

The aim of this study was to determine the long-term effects of perinatal PCP administration on the projection and local circuit neurons and NRG-1 expression in the cortex and hippocampus.

METHODS

Rats were treated on postnatal day 2 (P2), P6, P9, and P12 with either PCP (10 mg/kg) or saline. Morphological studies and determination of NRG-1 expression were performed at P70.

RESULTS

We demonstrate reduced densities of principal neurons in the CA3 and dentate gyrus (DG) subregions of the hippocampus and a reduction of major interneuronal populations in all cortical and hippocampal regions studied in PCP-treated rats compared with controls. For the first time, we show the reduced density of reelin- and somatostatin-positive cells in the cortex and hippocampus of animals perinatally treated with PCP. Furthermore, an increase in the numbers of perisomatic inhibitory terminals around the principal cells was observed in the motor cortex and DG. We also show that perinatal PCP administration leads to an increased NRG-1 expression in the cortex and hippocampus.

CONCLUSION

Taken together, our findings demonstrate that perinatal PCP administration increases NRG-1 expression and reduces the number of projecting and local circuit neurons, revealing complex consequences of NMDAR blockade.

Neonatal NMDA receptor blockade alters anxiety- and depression-related behaviors in a sex-dependent manner in mice

There is increasing evidence that N-methyl-D-aspartate (NMDA) receptor blockade in the neonatal period has a long-lasting influence on brain and behavior development and has been linked to an increased risk for neuropsychiatric disorders in later life. We sought to determine whether postnatal NMDA receptor blockade can affect normal development of body weight, corticosterone levels, anxiety- and depression-related behaviors in male and female mice in adulthood. For this purpose, male and female NMRI mice were treated with either saline or phencyclidine (PCP; 5 and 10 mg/kg, s.c.) on postnatal days (PND) 7, 9, and 11, and then subjected to different behavioral tests, including open field, elevated plus-maze, elevated zero-maze, light-dark box, tail suspension test and forced swimming test in adulthood. The results indicated that neonatal PCP treatment reduced body weight during neonatal and adulthood periods, and did not alter baseline corticosterone levels in both male and female mice. Moreover, this study obtained some experimental evidence showing the PCP at dose of 10 mg/kg increases stress-induced corticosterone levels, anxiety- and depression-related behaviors in males, while decreasing levels of anxiety without any significant effect on depression in female mice in adulthood. These data support the argument that neonatal NMDA receptor blockade can lead to behavioral abnormalities and psychiatric diseases in adulthood. Collectively, our findings suggest that neonatal exposure to PCP may have profound effects on the development of anxiety- and depression-related behaviors in a sex- and dose-dependent manner in mice.

Ontogenetic influence on rat susceptibility to lindane seizure after pretreatment with phencyclidine

The aim of the study was to determine the effects of early postnatal PCP treatment on the sensitivity of pubertal and adult rats to lindane proepileptogenic effects. Rat pups were treated with NaCl (0.9%) or PCP (10 mg/kg) at postnatal days 2, 6, 9 and 12. One control (NaCl-35) and one experimental (PCP-35) group have received lindane (4 mg/kg) at postnatal day 35, while others received lindane at postnatal day 65 (NaCl-65 and PCP-65). One week prior to lindane treatment three gold-plated EEG electrodes were implanted. Pubertal rats had significantly shorter latency time. After lindane, a prompt increase in power spectral density seen in PCP-treated groups vs. control was evident earlier in PCP-65 rats. The theta waves were significantly increased in PCP-35 and alpha rhythm in PCP-65 rats, when compared with corresponding controls. Postnatal PCP treatment increases the synchronization of brain electrical activity, thus contributing to the increased susceptibility to lindane.

Prenatal exposure to cigarette smoke causes persistent changes in the oxidative balance and in DNA structural integrity in rats submitted to the animal model of schizophrenia

Epidemiological studies have indicated that prenatal exposure to environmental insults can bring an increased risk of schizophrenia. The objective of our study was to determine biochemical parameters in rats exposed to cigarette smoke (CS) in the prenatal period, evaluated in adult offspring submitted to animal model of schizophrenia induced by acute subanaesthetic doses of ketamine (5 mg/kg, 15 mg/kg and 25 mg/kg). Pregnant female Wistar rats were exposed to 12 commercially filtered cigarettes per day, daily for a period of 28 days. We evaluated the oxidative damage in lipid and protein in the rat brain, and DNA damage in the peripheral blood of male adult offspring rats. To determine oxidative damage in the lipids, we measured the formation of thiobarbituric acid reactive species (TBARS) and the oxidative damage to the proteins was assessed by the determination of carbonyl groups content. We also evaluated DNA damage using single-cell gel electrophoresis (comet assay). Our results showed that rats exposed to CS in the prenatal period presented a significant increase of the lipid peroxidation, protein oxidation and DNA damage in adult age. We can observe that the animals submitted at acute doses of ketamine also presented an increase of the lipid peroxidation and protein oxidation at different doses and structures. Finally, we suggest that exposure to CS during the prenatal period affects two essential cerebral processes during development: redox regulation and DNA integrity, evaluated in adult offspring. These effects can leads to several neurochemical changes similar to the pathophysiology of schizophrenia.