Effect of pretreatment with risperidone on phencyclidine-induced disruptions in object recognition memory and prefrontal cortex parvalbumin immunoreactivity in the rat

Sub-chronic administration of phencyclidine to the rat induces enduring cognitive and pathophysiological changes that resemble some features of schizophrenia. The present study aimed to determine if concurrent administration of the atypical antipsychotic, risperidone, could attenuate the effect of phencyclidine on object recognition memory and parvalbumin-containing neurons in the prefrontal cortex. Rats were administered phencyclidine at a dose of 2mg/kg i.p. bi-daily for 1 week, or vehicle. Half of the phencyclidine group was concurrently treated with risperidone (0.5mg/kg i.p.) twice daily for 10 days, beginning 3 days before the start of phencyclidine administration. Novel object recognition memory and subsequent brain analysis were assessed 6 weeks post-phencyclidine treatment. Phencyclidine produced a deficit in object recognition memory as measured by the discrimination ratio. In addition, 6 weeks post-phencyclidine, analysis of brains showed a reduction in expression of parvalbumin-immunoreactive neurons in the prefrontal cortex, with specific deficits observed in the prelimbic region, but not infralimbic or cingulate cortices. Concurrent administration of risperidone showed no protective effects against these deficits. These results show the importance of the sub-chronic phencyclidine rat in modelling cognitive and prefrontal pathophysiology observed in schizophrenia, but suggest that concurrent risperidone is not neuroprotective in this model.

Olanzapine-induced weight gain in the rat: role of 5-HT2C and histamine H1 receptors

INTRODUCTION

Substantial increases in body weight can be induced by several antipsychotic drugs, most notably olanzapine and clozapine. Antagonism at certain receptors, particularly 5-HT2C and histamine H1 receptors, is implicated in this effect.

MATERIALS AND METHODS

We have investigated the contribution of effects at these receptors to olanzapine-induced weight gain occurring over 5 days following daily intraperitoneal drug injections in groups of eight female rats.

RESULTS

Olanzapine (2 mg/kg) and the 5-HT2C antagonist SB 243213 (1 mg/kg), but not the histamine H1 antagonist mepyramine (1 mg/kg), produced significant increases in percentage body weight above vehicle; olanzapine showed a significantly greater effect than SB 243213. Haloperidol (0.1 mg/kg) alone or with mepyramine had no significant effects on weight gain, while with SB 243213 and with both SB 243213 and mepyramine, it showed olanzapine-like increases in weight.

CONCLUSION

These results suggest that 5-HT2C receptor antagonism or inverse agonism, in the presence of D2 receptor antagonism, may contribute to olanzapine-induced weight gain.

Effect of acute tryptophan depletion on noradrenaline and dopamine in the rat brain

In human subjects, the acute tryptophan (TRP) depletion (ATD) paradigm has been shown to have effects on mood and cognition. It is assumed that these effects are mediated through the serotonin system. In this study, we have examined the effects of ATD on the central concentrations of the monoamine transmitters, noradrenaline (NA) and dopamine (DA) as well as on serotonin (5-HT). Effects on NA and DA could also affect mood and cognition. Following oral administration of TRP-containing (TRP+) and TRP-free (TRP-) amino acid mixtures, neurotransmitter concentrations and free plasma TRP concentrations were determined by High Performance Liquid Chromatography (HPLC) with electrochemical detection. Free plasma TRP was significantly and substantially reduced (79%) in rats given a TRP- amino acid mixture when compared with those given a TRP+ mixture. ATD also significantly decreased 5-HT and 5-hydroxyindolacetic acid in the frontal cortex, remaining cortex and hippocampus, but did not significantly reduce these in the striatum. Furthermore, ATD did not significantly alter the concentration of NA and DA in any brain region examined. This study demonstrates that the administration of a TRP- amino acid mixture in rats can reduce free plasma TRP to levels comparable to those reported in human studies. These results indicate that behavioural and cognitive changes produced by ATD in preclinical or clinical studies are likely to be due to specific effects on the serotonergic system.

Disturbances in social interaction occur along with pathophysiological deficits following sub-chronic phencyclidine administration in the rat

A sub-chronic administration of phencyclidine to the rat brings about enduring pathophysiological and cognitive changes that resemble some features of schizophrenia. The present study aimed to determine whether the behavioural consequence of this phencyclidine regime extends to a long-term disruption of social interaction that might provide a parallel with some negative symptoms of the disease. Rats were treated with phencyclidine (2mg/kg bi-daily for 1 week) or vehicle followed by a drug-free period. Social interaction was assessed 24h, 1 week, 3 weeks and 6 weeks post-treatment. A long-lasting disturbance of social behaviour was observed in the phencyclidine group, namely more contact and non-contact interaction with an unfamiliar target rat at all time points. Six weeks post-phencyclidine, analysis of brains showed a reduction in expression of parvalbumin immunoreactive neurons in the hippocampus with significant reductions localised to the CA1 and dentate gyrus regions. These results show that sub-chronic phencyclidine produces long-lasting disruptions in social interaction that, however, do not model the social withdrawal seen in patients with schizophrenia. These disturbances of social behaviour may be associated with concurrent pathophysiological brain changes.

Ziprasidone and aripiprazole attenuate olanzapine-induced hyperphagia in rats

Weight gain induced by some second-generation anti-psychotics such as olanzapine has emerged as a most debilitating side-effect. This study investigates whether co-administration with either ziprasidone or aripiprazole, which have little propensity to induce weight gain, can attenuate the hyperphagic effect of olanzapine. Female hooded-Lister rats (n=8 per group) were treated acutely with either vehicle, olanzapine (1 mg/kg), ziprasidone (1 mg/kg), aripiprazole (2 mg/kg) or olanzapine in combination with ziprasidone or aripiprazole and placed in automated locomotor activity (LMA) boxes with preweighed palatable mash. Food intake and LMA were measured for 60 min postdrug treatment. All olanzapine-treated groups demonstrated significant increases in food intake (P<0.001). This effect was attenuated following co-administration of olanzapine with either ziprasidone or aripiprazole (P<0.001), neither of which affected food intake alone. The lack of hyperphagia induced by aripiprazole and ziprasidone may reflect an inherent pharmacological mechanism preventing weight gain.

Influence of 5-HT2C receptor and leptin gene polymorphisms, smoking and drug treatment on metabolic disturbances in patients with schizophrenia

BACKGROUND

Obesity and metabolic syndrome are significant problems for patients taking antipsychotic drugs. Evidence is emerging of genetic risk factors.

AIMS

To investigate the influence of two candidate genes, smoking and drug treatment on obesity and metabolic syndrome in patients with schizophrenia.

METHOD

Patients (n=134) were assessed for measures of obesity, other factors contributing to metabolic syndrome, and two genetic polymorphisms (5-HT(2C) receptor -759C/T and leptin -2548A/G).

RESULTS

Neither genotype nor smoking was significantly associated with measures of obesity. However, both leptin genotype and smoking were significantly associated with metabolic syndrome. Significant interaction occurred between the genetic polymorphisms for effects on obesity, whereby a genotype combination increased risk. Drug treatment showed significant effects on measures of obesity and triglyceride concentrations; risperidone was associated with lower values than olanzapine or clozapine.

CONCLUSIONS

The findings suggest interacting genetic risk factors and smoking influence development of metabolic syndrome in patients on antipsychotic drugs.

Acute tryptophan depletion does not alter central or plasma brain-derived neurotrophic factor in the rat

Dietary induced acute tryptophan depletion (ATD) is used to reduce central serotonergic function and to investigate the role of serotonin (5-HT) in psychiatric illness. In healthy volunteers ATD produces working memory deficits and decreases mood in some studies. Brain-derived neurotrophic factor (BDNF) plays a role in both cognition and in the regulation of mood; however, the possible contribution of central BDNF changes to the effects of ATD has not been examined. Therefore, using a rat model we have examined the effect of amino acid mixture-induced ATD on plasma and central BDNF protein levels. ATD significantly reduced free-plasma TRP by 79% and central hippocampal 5-HT by 35% when compared to controls. However, plasma or central BDNF protein levels in the hippocampus and midbrain were not significantly altered by ATD. These results suggest that changes in central BDNF do not contribute to the cognitive or mood effects of ATD.

The effect of chronic antipsychotic treatment on sexual behaviour, hormones and organ size in the male rat

Antipsychotic drug-induced sexual dysfunction is an important and problematic side effect. We have investigated the effect of chronic antipsychotic treatment on sexual behaviour, sex hormones and genital organ size in the male rat. The following sexual functions were significantly impaired in both risperidone (2 mg/kg) and haloperidol (2 mg/kg) groups at 3 weeks: libido (assessed in mounting frequency and intromission), sexual arousability/motivation (in terms of latencies for mounting and intromission) and orgasm (in terms of latency for ejaculation). At 6 weeks, haloperidol also suppressed the 'hit ratio' (intromissions/mounts) as well as the above-mentioned parameters indicating erectile dysfunction. Risperidone had no significant effect on sexual function at 6 weeks. Compared with the control group, haloperidol and risperidone decreased the serum level of testosterone after 6 weeks but not after 3 weeks. The two drugs did not influence the serum level of leutenizing hormone (LH). At 3 weeks, the epididymis was significantly decreased below controls in both risperidone and haloperidol groups. At 6 weeks, the epididymis, seminal vesicle and prostate weights were significantly reduced in the haLoperidol group, but not in the risperidone group. The serum concentration of testosterone significantly correlated with sex organ weight, but not with sexual behaviours. These results suggest that sexual function, testosterone levels and genital tissue size in male rats were affected to different degrees by risperidone and haloperidol. These findings contribute to our understanding of antispsychotic drug-induced male sexual dysfunction.

The neuronal pathology of schizophrenia: molecules and mechanisms

There is an accumulation of evidence for abnormalities in schizophrenia of both the major neurotransmitter systems of the brain – those of GABA (γ-aminobutyric acid) and glutamate. Initial studies have found deficits in the putative neuronal marker, N-acetylaspartate, in a number of brain regions in schizophrenia. The animal models have provided some interesting correlates and discrepancies with these findings. The deficit in inhibitory interneurons within structures implicated in schizophrenic symptomatology may well have direct functional relevance, and can be induced by animal models of the disease such as subchronic phencyclidine administration or social isolation. Their association with these animal models suggests an environmental involvement. A loss of glutamatergic function in schizophrenia is supported by decreases in markers for the neuronal glutamate transporter in striatal structures that receive cortical glutamatergic projections. Deficits in the VGluT1 (vesicular glutamate transporter-1) in both striatal and hippocampal regions support this observation, and the association of VGluT1 density with a genetic risk factor for schizophrenia points to genetic influences on these glutamatergic deficits. Further studies differentiating neuronal loss from diminished activity and improved models allowing us to determine the temporal and causal relationships between GABAergic and glutamatergic deficits will lead to a better understanding of the processes underlying the neuronal pathology of schizophrenia.

Acute and chronic tryptophan depletion differentially regulate central 5-HT1A and 5-HT 2A receptor binding in the rat

RATIONALE

Tryptophan depletion is used to reduce central serotonergic function and to investigate its role in psychiatric illness. Despite widespread clinical use, its effects on serotonin (5-HT) receptors have not been well characterized.

OBJECTIVE

The aim of this study was to examine the effect of acute (ATD) and chronic tryptophan depletion (CTD) on free-plasma tryptophan (TRP), central TRP and 5-HT and brain 5-HT(1A) and 5-HT(2A) receptor binding in the rat.

METHODS

TRP and 5-HT were measured by high-performance liquid chromatography and receptor levels determined by homogenate radioligand binding and in-vitro receptor autoradiography.

RESULTS

Free-plasma TRP, central TRP and central 5-HT levels were significantly and similarly reduced by ATD and 1- and 3-week CTD compared to controls. ATD significantly reduced 5-HT(1A) binding in the dorsal raphe (14%) but did not significantly alter postsynaptic 5-HT(1A) binding (frontal cortex, remaining cortex and hippocampus) or 5-HT(2A) binding (cortex and striatum). One-week CTD did not significantly alter cortical 5-HT(2A) binding or postsynaptic 5-HT(1A) binding. Furthermore, 3-week CTD did not significantly alter 5-HT(1A) binding but significantly increased cortical 5-HT(2A) binding without affecting striatal or hippocampal levels. In the CTD 1 and 3-week groups, rat body weight was significantly decreased as compared to controls. However, weight loss was not a confounding factor for decreased cortical 5-HT(2A)-receptor binding.

CONCLUSION

ATD-induced reduction in somatodendritic 5-HT(1A) autoreceptor binding may represent an intrinsic 'homeostatic response' reducing serotonergic feedback in dorsal raphe projection areas. In contrast, the increase in 5-HT(2A) receptor after CTD may be a compensatory response to a long-term reduction in 5-HT.

Sub-chronic psychotomimetic phencyclidine induces deficits in reversal learning and alterations in parvalbumin-immunoreactive expression in the rat

Acute administration of the psychotomimetic phencyclidine (PCP) can mimic some features of schizophrenia, while a repeated treatment regimen of PCP may provide a more effective way to model in animals the enduring cognitive dysfunction observed in many schizophrenic patients. The present study aims to investigate behavioural and neuropathological effects of sub-chronic PCP administration. The cognitive deficit induced by sub-chronic PCP was examined using a previously established operant reversal-learning paradigm. Subsequently, the effect of sub-chronic PCP on parvalbumin-immunoreactive (parvalbumin-IR) neurons was assessed using immunohistochemical techniques. Rats were trained to respond for food in an operant reversal-learning paradigm for approximately 6 weeks, followed by sub-chronic administration of PCP (2mg/kg) or vehicle twice daily for 7 days followed 7 days later by behavioural testing. Six weeks post PCP, brains were analysed using immunohistochemical techniques to determine the size and density of parvalbumin-IR in the frontal cortex and hippocampus. Sub-chronic PCP significantly reduced (p <0.001) percentage correct responding in the reversal phase relative to the initial phase, an effect that persisted throughout the experimental period (4 weeks). The density of parvalbumin-IR neurons was reduced in the hippocampus, with significant reductions in the dentate gyrus and CA2/3 regions (p <0.001). There were significant changes in the frontal cortex, with a reduction (p <0.01) in the M1 (motor area 1) region and increases in the M2 (motor area 2) region and cingulate cortex (p <0.01-p <0.001). These results parallel findings of profound hippocampal and more subtle cortical deficits of parvalbumin-IR neurons in schizophrenia, and provide evidence to suggest that sub-chronic PCP can induce a lasting cognitive deficit, an effect that may be related to the observed neuronal deficits.

5-HT2C receptor gene polymorphisms associated with antipsychotic drug action alter promoter activity

Polymorphisms within the 5-HT(2C) receptor gene promoter have been associated with several physiological and psychiatric phenotypes. Notably, the -759T allele has been associated with resistance to antipsychotic induced weight gain. This study assessed the activity of four promoter haplotypes expressed as luciferase constructs in the SH-SY5Y human neuroblastoma cell line in the presence or absence of a constitutively active 5-HT(2C) receptor. The presence of either -759T or -697C alleles reduced promoter activity. In addition a haplotype associated with resistance to antipsychotic induced weight showed under activity compared to the most common haplotype. In the presence of the 5-HT(2C) receptor a similar pattern of promoter activity was observed. Both -759C/T and -697G/C polymorphic sites are likely to play a role in basal promoter activity. Resistance to weight gain may, in part, be mediated by the consequences of reduced 5-HT(2C) receptor expression.

Deficits in parvalbumin and calbindin immunoreactive cells in the hippocampus of isolation reared rats

Post-mortem studies have provided evidence for abnormalities of the gamma-aminobutyric acid (GABA)-ergic system in schizophrenia. The calcium-binding proteins (CBPs), parvalbumin (PV), calbindin (CB) and calretinin (CR) can be used as markers for specific subpopulations of GABAergic neurons in the brain. Isolation rearing of rats is a non-pharmacological, non-lesion manipulation that leads to deficits in prepulse inhibition of the startle reflex (PPI) and other behavioural and neurochemical alterations reminiscent of schizophrenia. Female rats were reared in social housing (groups of three) or singly for 11 weeks post weaning and PPI was measured. Brains were removed and hippocampal CBP- containing neurons determined following immunocytochemical staining. Compared to socially housed rats, isolated rats exhibited PPI deficits and reductions in PV and CB-immunoreactive cells in the hippocampus, with no significant change in CR. These findings demonstrate selective abnormalities of sub-populations of GABAergic interneurons in the hippocampus of isolation reared rats, which resemble the neuronal deficits seen in this region in schizophrenia.

Deficits of neuronal glutamatergic markers in the caudate nucleus in schizophrenia

Abnormal glutamate neurotransmission has been implicated in the pathophysiology of schizophrenia. In the present study we investigated two potential neuronal glutamatergic markers, the Excitatory Amino Acid Transporter 3 (EAAT3) and the Vesicular Glutamate Transporter 1 (VGluT1), in post-mortem striatal tissue from control subjects and from subjects with schizophrenia (n = 15 per group). We also investigated the possible influence of chronic antipsychotic administration (typical and atypical) on striatal VGluT1 expression in the rat brain. We found deficits in EAAT3 in all striatal regions examined in schizophrenia when compared to controls. Following correction for confounding factors (post-mortem interval), these deficits only remained significant in the caudate nucleus (p = 0.019). We also found significant deficits in VGluT1 in the caudate nucleus (p = 0.009) in schizophrenia. There were no significant differences in VGluT1 in the striatum of antipsychotic treated rats when compared to their vehicle treated controls. The data provides additional evidence for a glutamatergic synaptic pathology in the caudate nucleus in schizophrenia and may reflect a loss of glutamatergic cortico-striatal pathways. The absence of an effect of antipsychotic administration on VGluT1 indicates that the deficits in schizophrenia are unlikely to be a consequence of pharmacotherapy and thus likely to be a correlate of the disease process.

Effect of 5-HT1A receptor gene polymorphism on negative and depressive symptom response to antipsychotic treatment of drug-naive psychotic patients

OBJECTIVE

The serotonin 5-HT(1A) receptor may modulate some of the negative, cognitive, and affective symptoms of schizophrenia and is a potential target of action of some antipsychotic drugs. A functional polymorphism in the promoter region of the 5-HT(1A) receptor gene is associated with depression and suicidal behavior. The authors sought to determine whether this polymorphism influences symptom response to antipsychotic drug treatment.

METHOD

Sixty-three drug-naive patients with first-episode psychosis who were genotyped for the -1019C/G polymorphism were recruited for this study and received standard care. The Positive and Negative Syndrome Scale and the Calgary Depression Scale were used to monitor symptom changes over 3 months.

RESULTS

The polymorphism was associated with, and accounted for much of the variance in, changes in negative and depressive symptoms but not positive symptoms.

CONCLUSIONS

These findings identify an important genetic factor predicting much of the response in negative and depressive symptoms to antipsychotic drug treatment.

Selective increases in the cytokine, TNFalpha, in the prefrontal cortex of PCP-treated rats and human schizophrenic subjects: influence of antipsychotic drugs

The psychotomimetic drug phencyclidine (PCP) induces symptoms closely related to those of schizophrenia in humans. In order to test the hypothesis that cytokines may be involved in the aetiology and treatment of schizophrenia, this study investigated the levels of cytokine mRNAs in rat brain after acute and chronic administration of PCP, in the presence and absence of antipsychotic drugs. The levels of the mRNAs encoding TNF, IL-2, IL-6, TGF 1, 2, 3, IL-3 and GM-CSF were measured in the prefrontal cortex, cortex, hippocampus, ventral and dorsal striatum regions of male hooded Long Evans rats after acute drug administration. Antipsychotic drugs and PCP significantly reduced the levels of TNF in the prefrontal cortex compared to vehicle-treated animals, whilst other cytokines remained unchanged. In addition, significant reductions in the levels of TNF mRNA in the prefrontal cortex still occurred 24h after acute PCP administration. However, levels of TNF mRNA were restored to control values after chronic PCP treatment, whereas increased expression was detected in animals co-administered with haloperidol. Levels of TNF mRNA were also found to be significantly increased in the prefrontal cortex of schizophrenic subjects. The relationship between TNF levels and schizophrenia are discussed.

Pharmacogenetics of schizophrenia

There is substantial unexplained interindividual variability in the drug treatment of schizophrenia. A substantial proportion of patients respond inadequately to antipsychotic drugs, and many experience limiting side effects. As genetic factors are likely to contribute to this variability, the pharmacogenetics of schizophrenia has attracted substantial effort. The approaches have mainly been limited to association studies of polymorphisms in candidate genes, which have been indicated by the pharmacology of antipsychotic drugs. Although some advances have been made, particularly in understanding the pharmacogenetics of some limiting side effects, genetic prediction of symptom response remains elusive. Nevertheless, with improvements in defining the response phenotype in carefully assessed and homogeneous subject groups, the near future is likely to see the identification of genetic predictors of outcome that may inform the choice of pharmacotherapy.

The 5-HT2C receptor and antipsychoticinduced weight gain - mechanisms and genetics

The mechanisms underlying weight gain resulting from antipsychotic drugs are not fully understood, although antagonism of the 5-HT2C receptor is likely to contribute. Animal studies indicate that the drugs most likely to cause weight gain, clozapine and olanzapine, have direct effects on the NPY-containing neurons of the hypothalamus; these neurons mediate the effects of the circulating anorexigenic hormone leptin on the control of food intake. The substantial differences between individuals in the extent of antipsychotic-induced weight gain suggest that genetic factors may be important. We have been studying pharmacogenetic correlates and find that a common 5-HT2C receptor promoter region polymorphisms demonstrates strong associations with weight gain in two first episode psychotic samples. In both series, we have found further association of antipsychotic drug-induced weight gain with a common and functional polymorphism of the gene for leptin. Along with initial BMI, these two pharmacogenetic factors account for almost 30% of the variance in drug-induced weight gain. Interestingly, the 5-HT2C polymorphism appears to determine levels of circulating leptin, providing a potential mechanism underlying the genetic association of the 5-HT2C receptor with weight gain. We have undertaken functional studies of haplotypes of the 5-HT2C promoter region and find the allele associated with protection from weight gain results in reduced promoter activity. These findings demonstrate the value of pharmacogenetics in determining liability to a major side effect of antipsychotic treatment, and indicate both the molecular and physiological mechanisms underlying this side effect.

Clozapine, but not haloperidol, increases neuropeptide Y neuronal expression in the rat hypothalamus

Many atypical antipsychotic drugs, such as clozapine, can induce significant weight gain which can have serious implications for drug compliance and morbidity. Food intake and weight gain are regulated primarily by the hypothalamus; the arcuate nucleus (ARC) of the hypothalamus is the region initially mediating the effects of circulating hormones on food intake. Neuropeptide Y (NPY) is an important hypothalamic peptide involved in body weight regulation. Immunohistochemical staining of NPY in the ARC was carried out in male Sprague-Dawley rats treated with haloperidol (1.5 mg/kg, i.p.) or clozapine (25 mg/kg, i.p.) for 3 weeks. Clozapine, but not haloperidol, produced an increase in NPY immunoreactivity in the ARC, suggesting that effects on NPY may be involved in increases in body weight following clozapine treatment.

The effect of atypical and classical antipsychotics on sub-chronic PCP-induced cognitive deficits in a reversal-learning paradigm

Phencyclidine (PCP), an NMDA antagonist, has been shown to mimic some aspects of schizophrenia including positive, negative and cognitive symptoms. Previous studies in this laboratory have shown a selective reversal-learning deficit following acute PCP administration, a deficit that is attenuated by atypical, but not classical, antipsychotic treatment. However, acute PCP has limitations for modelling the chronic psychotic illness and persistent cognitive deficits observed in many schizophrenic patients. Therefore, the aim of this study was to examine the cognitive deficit induced by PCP over a longer term using a previously established operant reversal-learning procedure. Moreover, the efficacy of the atypical antipsychotics clozapine, ziprasidone and olanzapine to reverse the sub-chronic PCP deficit was compared with that of the classical antipsychotics, haloperidol and chlorpromazine. Female hooded-Lister rats were trained to respond for food using an operant reversal-learning paradigm. When animals achieved criterion of 90% correct responding they were treated with PCP (2mg/kg) or vehicle twice daily for 7 days, and 7 days later tested for their cognitive ability. PCP induced a significant impairment in the reversal phase relative to the initial phase of the task. Acute ziprasidone (2.5mg/kg), olanzapine (1.5mg/kg) and clozapine (5mg/kg) produced a significant attenuation of the impairment induced by sub-chronic PCP in the reversal phase. In marked contrast to these effects, acute administration of the classical agents haloperidol (0.05 mg/kg) and chlorpromazine (2mg/kg) failed to significantly reverse the PCP-induced cognitive impairment. These data clearly demonstrate that sub-chronic PCP produces enduring and persistent cognitive deficits, effects that are significantly attenuated by atypical but not classical antipsychotics.

Antioxidant capacity in postmortem brain tissues of Parkinson's and Alzheimer's diseases

Oxidative stress has been associated with damage and progressive cell death that occurs in neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). The aim of this study was to investigate the antioxidant capacity in postmortem motor cortex (MC), nucleus caudatus (NC), gyrus temporalis (GT) and substantia nigra (SN) from controls (C) and patients with PD and AD. The initial samples consisted of 68 subjects of PD, AD and C. Brains were matched for age, sex and postmortem time. Brain tissue was homogenized in a phosphate buffer pH 7.3 and separated with two-step centrifugation at 15,000rpm for 30 min and 15,000 rpm for 10 min at 4 degrees C. Antioxidant capacity in the supernatants was measured using the oxygen radical absorbance assay (ORAC). The results showed that in the SN of parkinsonian's brain the balance between production of free radicals and the neutralization by a complex antioxidant system is disturbed. No changes in the antioxidant capacity of postmortem MC and NC of parkinsonian's brain in comparison with C were found. In the SN of parkinsonian's brain, antioxidant capacity seems to be lower in comparison with C (p < 0.05). Antioxidant capacity against peroxyl radical showed that MC of AD patients was lower than in the MC of C (p < 0.005). In NC of AD patients the antioxidant capacity against hydroxyl radical was increased in comparison with C (p < 0.04). No changes in the antioxidant capacity were found in brain tissues of AD in comparison with C, when CuSO4 was used as a free radical generator.