Neurochemical and Behavioral Effects of a New Hallucinogenic Compound 25B-NBOMe in Rats.

4-Bromo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25B-NBOMe) is a hallucinogen exhibiting high binding affinity for 5-HT2A/C serotonin receptors. In the present work, we investigated its effect on dopamine (DA), serotonin (5-HT), acetylcholine (ACh), and glutamate release in the rat frontal cortex, striatum, and nucleus accumbens. Hallucinogenic activity, impact on cognitive and motor functions, and anxiogenic/anxiolytic properties of this compound were also tested. The release of DA, 5-HT, ACh, and glutamate was studied using microdialysis in freely moving animals. Hallucinogenic activity was investigated using head and body twitch response (WDS), cognitive functions were examined with the novel object recognition test (NOR), locomotor activity was studied in the open field (OF), while anxiogenic/anxiolytic effect was tested using the light/dark box (LDB). Neurotoxicity was evaluated with the comet assay. 25B-NBOMe increased DA, 5-HT, and glutamate release in all studied brain regions, induced hallucinogenic activity, and lowered the recognition index (Ri) vs. control in the NOR test. It also decreased locomotor activity of rats in the OF test. The effect of 25B-NBOMe in the NOR test was inhibited by scopolamine. In the LDB test, the time spent in the dark zone was longer in comparison to control and was dose-dependent. In contrast to MDMA, 25B-NBOMe showed subtle genotoxic effect observed in the comet assay.Our findings indicate that 25B-NBOMe shows hallucinogenic activity in the wide range of doses. The changes in neurotransmitter levels may be related to 25B-NBOMe affinity for 5-HT2A receptor. Alterations in the NOR, OF, and LDB indicate that 25B-NBOMe impacts short-term memory, locomotion, and may be anxiogenic.

Sensitivity to negative and positive feedback as a stable and enduring behavioural trait in rats.

RATIONALE: According to psychological theories, cognitive distortions play a pivotal role in the aetiology and recurrence of mood disorders. Although clinical evidence for the coexistence of depression and altered sensitivity to performance feedback is relatively coherent, we still do not know whether increased or decreased sensitivity to positive or negative feedback is associated with 'pro-depressive' profile in healthy subjects. OBJECTIVE: Our research has been designed to answer this question, and here, we present the first steps in that direction. METHODS: Using a rat version of the probabilistic reversal-learning (PRL) paradigm, we evaluated how sensitivity to negative and positive feedback influences other cognitive processes associated with mood disorders, such as motivation in the progressive ratio schedule of reinforcement (PRSR) paradigm, hedonic status in the sucrose preference (SP) test, locomotor and exploratory activity in the open field (OF) test, and anxiety in the light/dark box (LDB) test. RESULTS: The results of our study demonstrated for the first time that in rodents, sensitivity to negative and positive feedback could be considered a stable and enduring behavioural trait. Importantly, we also showed that these traits are independent of each other and that trait sensitivity to positive feedback is associated with cognitive flexibility in the PRL test. The computational modelling results also revealed that in animals classified as sensitive to positive feedback, the α learning rates for both positive and negative reward prediction errors were higher than those in animals classified as insensitive. We observed no statistically significant interactions between sensitivity to negative or positive feedback and the parameters measured in the PRSR, SP, OF or LDB tests. CONCLUSIONS: Further studies using animal models of depression based on chronic stress should reveal whether sensitivity to feedback is a latent trait that when interacts with stressful life events, could produce correlates of depressive symptoms in rats.

Correction to: the Effects of Exposure to Mephedrone During Adolescence on Brain Neurotransmission and Neurotoxicity in Adult Rats.

Acknowledgments: This study was supported by the Grant No 2013/09/B/NZ7/04104 from the National Science Center (Poland).

Effects of exposure to 5-MeO-DIPT during adolescence on brain neurotransmission and neurotoxicity in adult rats.

PURPOSE: Tryptamine hallucinogen 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is a serotonin transporter inhibitor with high affinity for serotonin 5-HT1A and 5-HT2A/C receptors. We showed previously that 5-MeO-DIPT in a single dose increased neurotransmitter release in brain regions of rats and elicited single- and double-strand DNA breaks. Herein we investigated the effects of repeated-intermittent 5-MeO-DIPT administration in adolescence on dopamine (DA), serotonin (5-HT) and glutamate release in brain regions of adult rats. Furthermore, we examined caspase-3 activity, oxidative DNA damage, the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels, and cell viability. METHODS: Neurotransmitter release was measured by microdialysis in freely moving animals. Caspase-3 activity was assessed colorimetrically, and oxidative DNA damage with the comet assay, while the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels were assessed by real-time polymerase chain reaction. Cell viability was studied in SH-SY5Y and Hep G2 cells by the MTT test. RESULTS: We observed changed responses of DA, 5-HT and glutamate neurons to a challenge dose of 5-MeO-DIPT when animals were treated repeatedly in adolescence with this hallucinogen. The basal extracellular levels of DA and 5-HT were decreased in the striatum and nucleus accumbens, while glutamate level was increased in the nucleus accumbens and frontal cortex. The damage of cortical DNA, increased Gpx3 and Sod1 mRNA expression and affected caspase-3 activity were also observed. Furthermore, decreased Ht1a and Ht2a mRNA expression in the frontal cortex and marked cytotoxicity of 5-MeO-DIPT were found. CONCLUSIONS: These results suggest that 5-MeO-DIPT given repeatedly during adolescence affects brain neurotransmission and shows neurotoxic potential observed in adult animals.

Using rodents to model abnormal sensitivity to feedback in depression.

Depressive disorder accounts for a substantial proportion of psychiatric problems across the globe and has a devastating impact on quality of life and occupational function. Psychological models of depression emphasize the causal role of cognitive distortions in this disease, and cognitive problems have been included in the diagnostic criteria for depressive episodes. Here, we focus on recent progress in preclinical modelling of aberrations in one of the most important neurocognitive mechanisms involved in the manifestation of depression - abnormal sensitivity to positive and negative feedback. First, we summarize the recent advances in understanding neurocognitive mechanisms of aberrant feedback sensitivity in depression and underlying neurobiological substrates. Second, by combining behavioural, neurochemical, neuroanatomical and pharmacological approaches, we evaluate the translational value of the probabilistic reversal-learning (PRL) task, a behavioural paradigm that enables investigation of correlates of feedback sensitivity in humans and animals. Finally, we identify and discuss directions for future investigation, including cognitive biomarkers of depression and resilience to stress based on feedback sensitivity and personalized treatment targets.

The effect of chronic co-treatment with risperidone and novel antidepressant drugs on the dopamine and serotonin levels in the rats frontal cortex.

BACKGROUND: Preclinical and clinical studies have suggested a beneficial effect of combination treatment with atypical antipsychotic drugs and antidepressants (ADs) in schizophrenia and in drug-resistant depression. METHODS: In the present study, we investigated the effect of chronic administration of risperidone and ADs (escitalopram or mirtazapine), given separately or jointly on the extracellular levels of dopamine (DA) and serotonin (5-HT) in the rat frontal cortex. The animals were administered risperidone (0.2mg/kg) and escitalopram (5mg/kg) or mirtazapine (10mg/kg) repeatedly for 14days. The release of monoamines in the rat frontal cortex was evaluated using a microdialysis, and DA and 5-HT levels were assayed by HPLC. We also measured the locomotor activity, catalepsy and recognition memory in these rats. RESULTS: Chronic risperidone treatment (0.2mg/kg) increased the extracellular levels of DA and 5-HT. Co-treatment with risperidone and escitalopram (5mg/kg) or mirtazapine (10mg/kg) more efficiently increased the release of 5-HT but not DA in the rat frontal cortex, as compared to drugs given alone. Moreover, risperidone, escitalopram and mirtazapine given alone or in combination significantly decreased the locomotor activity and only mirtazapine increased the catalepsy evoked by risperidone. Combined treatment with risperidone and ADs impaired recognition memory in these rats. CONCLUSIONS: The obtained results suggest that chronic co-administration of risperidone and escitalopram or mirtazapine more efficiently increased 5-HT release in the rat frontal cortex as compared to drugs given alone and suggest that this effect may be of importance to the pharmacotherapy of schizophrenia and drug-resistant depression.

The effect of repeated-intermittent exposure to 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) during adolescence on learning and memory in adult rats.

BACKGROUND: According to the European Drug Report, the use of novel psychoactive substances (NPS) is constantly growing. NPS are widely abused by human adolescent subjects. 5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is one of the most frequently used hallucinogenic NPS. 5-MeO-DIPT intoxication results in hallucinations, vomiting, and tachycardia. Long-term exposure to 5-MeO-DIPT was reported to lead to development of post-hallucinogenic perception disorder. The aim of the present study was to determine whether repeated-intermittent administration of 5-MeO-DIPT during adolescence affects learning and memory in adult rats. METHODS: Rats were treated with 5-MeO-DIPT in a dose of 2.5mg/kg from 30 to 33 and 37 to 40 Postnatal Day (PND). The experiments were conducted when the animals reached 90 PND. The effect of 5-MeO-DIPT on cognitive functions was assessed using the novel object recognition, open field, and serial pattern learning (SPL) tests. RESULTS: Repeated-intermittent exposure to 5-MeO-DIPT during adolescence decreased the number of crossings in the open field test at adulthood. Moreover, 5-MeO-DIPT treatment impaired adult rats' learning in the SPL test. There was no change in the novel object recognition test. CONCLUSIONS: The present results show that the performance of adult rats treated with 5-MeO-DIPT during adolescence was impaired in the open field test, which indicates the attenuated exploratory activity. 5-MeO-DIPT treatment undermined adult rats' performance in the serial pattern learning test, suggesting impairment of long term memory and cognitive flexibility. The present study showed that the exposure to 5-MeO-DIPT during adolescence might lead to long-lasting behavioral changes which persisted long after the exposure period.

The Effects of Exposure to Mephedrone During Adolescence on Brain Neurotransmission and Neurotoxicity in Adult Rats.

According to the European Drug Report (2016), the use of synthetic cathinones, such as mephedrone, among young people has rapidly increased in the last years. Studies in humans indicate that psychostimulant drug use in adolescence increases risk of drug abuse in adulthood. Mephedrone by its interaction with transporters for dopamine (DAT) and serotonin (SERT) stimulates their release to the synaptic cleft. In animal studies, high repeated doses of mephedrone given to adolescent but not adult mice or rats induced toxic changes in 5-hydroxytryptamine (5-HT) neurons. The aim of our study was to investigate the effects of mephedrone given in adolescence on brain neurotransmission and possible neuronal injury in adult rats. Adolescent male rats were given mephedrone (5 mg/kg) for 8 days. In vivo microdialysis in adult rats showed an increase in dopamine (DA), 5-HT, and glutamate release in the nucleus accumbens and frontal cortex but not in the striatum in response to challenge dose in animals pretreated with mephedrone in adolescence. The 5-HT and 5-hydroxyindoleacetic acid contents decreased in the striatum and nucleus accumbens while DA turnover rates were decreased in the striatum and nucleus accumbens. The oxidative damage of DNA assessed with the alkaline comet assay was found in the cortex of adult rats. Therefore, the administration of repeated low doses of mephedrone during adolescence does not seem to induce injury to 5-HT and DA neurons. The oxidative stress seems to be responsible for possible damage of cortical cell bodies which causes maladaptive changes in serotonergic and dopaminergic neurons.

Risperidone and escitalopram co-administration: A potential treatment of schizophrenia symptoms with less side effects.

BACKGROUND: Schizophrenia is a psychiatric disorder characterized by positive and negative symptoms often accompanied by depression and cognitive deficits. Positive symptoms, like delusions and hallucinations are caused by an excess of dopamine (DA) signaling and are treated with the second generation antipsychotic drugs. Negative symptoms of schizophrenia are represented by social withdrawal, apathy and blunted emotional response. It was demonstrated that co-administration of risperidone and selective serotonin reuptake inhibitors alleviated depressive symptoms and cognitive dysfunction in animal models of schizophrenia. Moreover, combination of fluoxetine or mirtazapine with risperidone increased DA and 5-hydroxytryptamine (5-HT) release in the rat frontal cortex more potently than either drug given separately. The present study aimed to investigate whether combination of risperidone and escitalopram is effective in increasing DA and 5-HT release. METHODS: The extracellular level of neurotransmitters in the rat frontal cortex and nucleus accumbens was examined using microdialysis in freely moving animals. The dialysate concentration of DA and 5-HT was assayed by HPLC. RESULTS: It was found that risperidone (0.2 and 1mg/kg) and escitalopram (5 and 10mg/kg) given together significantly increased cortical DA and 5-HT levels and were more efficient in enhancing neurotransmitter concentrations than any single-drug treatment. A similar effect on DA and 5-HT release was observed in the nucleus accumbens after administration of risperidone (1mg/kg) and escitalopram (5mg/kg). CONCLUSIONS: The present study demonstrates that co-administration of risperidone and escitalopram may be used to treat positive and negative symptoms of schizophrenia and will allow to minimize the drugs' side effects.

Neurochemical and behavioral studies on the 5-HT1A-dependent antipsychotic action of the mGlu4 receptor agonist LSP4-2022.

LSP4-2022 is a novel, orthosteric agonist of mGlu4 receptor that induces antipsychotic-like activity in animal studies. In the present study, the involvement of 5-HT1A receptors in LSP4-2022-induced antipsychotic actions and the neurochemical background of that interaction were investigated. In several behavioral tests the actions of effective doses of the compound (0.5-2 mg/kg) were antagonized via the administration of the 5-HT1A antagonist WAY100635 (0.1 mg/kg). The co-administration of sub-effective dose of the 5-HT1A agonist (R)-(S)-8-OH-DPAT (0.01 mg/kg) intensified the activity of ineffective doses of LSP4-2022, having no influence on the efficacy of the active doses. The co-administration of effective doses of both compounds did not intensify each other's action. In the microdialysis in vivo tests, MK-801 (0.6 mg/kg) induced an enhancement of the release of dopamine, serotonin, glutamate and GABA in the prefrontal cortex. Administration of LSP4-2022 (2 mg/kg) abolished this MK-801-induced effect on neurotransmitter release. Co-administration with WAY100635 (0.1 mg/kg), a 5-HT1A antagonist, completely (dopamine, serotonin) or partially (glutamate, GABA) counteracted this LSP4-2022-induced effect. Subsequently, the patch-clamp recordings of spontaneous EPSCs were performed. sEPSCs were evoked in slices from the mouse prefrontal cortex by DOI (10 µM). LSP4-2022 (2.5; 5 and 10 µm) reversed DOI-induced changes in both the frequency and amplitude of the sEPSCs, but the more robust effect on the frequency was observed. The administration of WAY100635 had no effect on the LSP4-2022-induced effects on sEPSCs, indicating that the mGlu4-5-HT1A interaction does not occur via single-neuron signaling but involves neuronal circuits that regulate neurotransmitter release. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Neurotoxic Effects of 5-MeO-DIPT: A Psychoactive Tryptamine Derivative in Rats.

5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT, 'foxy') is one of the most popular tryptamine hallucinogens in the illicit drug market. It produces serious adverse effects, but its pharmacological profile is not well recognized. In vitro data have shown that 5-MeO-DIPT acts as a potent serotonin transporter (SERT) inhibitor and displays high affinity at serotonin 5-HT1A, 5-HT2A, and 5-HT2C receptors. In this study, using microdialysis in freely moving rats, we examined the effect of 5-MeO-DIPT on dopamine (DA), serotonin (5-HT), and glutamate release in the rat striatum, nucleus accumbens, and frontal cortex. In search of a possible neurotoxic effect of 5-MeO-DIPT, we measured DA and 5-HT tissue content in the above rat brain regions and also determined the oxidative DNA damage with the comet assay. Moreover, we tested drug-elicited head-twitch response and a forepaw treading induced by 8-OH-DPAT. 5-MeO-DIPT at doses of 5, 10, and 20 mg/kg increased extracellular DA, 5-HT, and glutamate level but the differences in the potency were found between brain regions. 5-MeO-DIPT increased 5-HT and decreased 5-HIAA tissue content which seems to result from SERT inhibition. On the other hand, a decrease in DA, DOPAC, and HVA tissue contents suggests possible adaptive changes in DA turnover or damage of DA terminals by 5-MeO-DIPT. DNA single and double-strand breaks persisted up to 60 days after the treatment, indicating marked neurotoxicity of 5-MeO-DIPT. The induction of head-twitch response and potentiation of forepaw treading induced by 8-OH-DPAT indicate that hallucinogenic activity seems to be mediated through the stimulation of 5-HT2A and 5-HT1A receptors by 5-MeO-DIPT.

Alterations of Bio-elements, Oxidative, and Inflammatory Status in the Zinc Deficiency Model in Rats.

Our previous study showed that dietary zinc restriction induces depression-like behavior with concomitant up-regulation of the N-methyl-D-aspartate receptor (NMDAR). Because metal ions, oxidative stress, and inflammation are involved in depression/NMDAR function, in the present study, bio-elements (zinc, copper, iron, magnesium, and calcium), oxidative (thiobarbituric acid-reactive substances; protein carbonyl content), and inflammatory (IL-1α, IL-1ß) factors were measured in serum, hippocampus (Hp), and prefrontal cortex (PFC) of male Sprague-Dawley rats subjected to a zinc-adequate (ZnA) (50 mg Zn/kg) or a zinc-deficient (ZnD) (3 mg Zn/kg) diet for 4 or 6 weeks. Both periods of dietary zinc restriction reduced serum zinc and increased serum iron levels. At 4 weeks, lowered zinc level in the PFC and Hp as well as lowered iron level in the PFC of the ZnD rats was observed. At 6 weeks, however, iron level was increased in the PFC of these rats. Although at 6 weeks zinc level in the PFC did not differ between the ZnA and ZnD rats, extracellular zinc concentration after 100 mM KCl stimulation was reduced in the PFC of the ZnD rats and was accompanied by increased extracellular iron and glutamate levels (as measured by the in vivo microdialysis). The examined oxidative and inflammatory parameters were generally enhanced in the tissue of the ZnD animals. The obtained data suggest dynamic redistribution of bio-elements and enhancement of oxidative/inflammatory parameters after dietary zinc restriction, which may have a link with depression-like behavior/NMDAR function/neurodegeneration.

Effect of Some Psychoactive Drugs Used as 'Legal Highs' on Brain Neurotransmitters.

New psychoactive "designer drugs" are synthetic compounds developed to provide similar effects to illicit drugs of abuse, but not subjected to legal control. The rapidly changing legal status of novel psychoactive drugs triggers the development of new compounds, analogs of well-known amphetamine or mescaline. New designer drugs used as substitutes in ecstasy pills are the least investigated and can cause life-threatening effects on users. The aim of our research was to examine the effects of acute administration of 4-methoxyamphetamine (PMA, 5 and 10 mg/kg), 4-methoxy-N-methylamphetamine (PMMA, 5 and 10 mg/kg), and mephedrone (MEPH, 5, 10 and 20 mg/kg) on extracellular and tissue level of dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites in rat brain, by microdialysis method in freely moving animals and HPLC. Similarly to 3,4-methylenedioxymethamphetamine (MDMA, 5 and 10 mg/kg) PMA, PMMA and MEPH enhanced the release of DA and 5-HT in rat striatum, nucleus accumbens, and frontal cortex. DA tissue content was increased by MEPH and PMMA in striatum, by MEPH, PMA, and PMMA in nucleus accumbens, and by PMA in frontal cortex. Instead, cortical DA level was decreased by MEPH and PMMA. MEPH did not influence 5-HT tissue level in striatum and nucleus accumbens, but decreased its level in frontal cortex. PMMA increased 5-HT content in striatum, while PMA enhanced it in nucleus accumbens and frontal cortex. Observed changes in brain monoamines and their metabolites by new psychoactive drugs suggest that these drugs may be capable of development of dependence. Further experiments are needed to fully investigate the neurotoxic and abuse potential of those drugs.

The antipsychotic-like effects in rodents of the positive allosteric modulator Lu AF21934 involve 5-HT1A receptor signaling: mechanistic studies.

RATIONALE: Diverse preclinical studies suggest the potential therapeutic utility of the modulation of the glutamatergic system in brain via metabotropic glutamate (mGlu) receptors. Lu AF21934, a positive allosteric modulator of the mGlu4 receptor, was previously shown to reverse behavioral phenotypes in animal models thought to mimic positive, negative, and cognitive symptoms of schizophrenia. OBJECTIVES: To begin elucidating the brain circuitry involved in mGlu4 receptor pharmacology and add mechanistic support to Lu AF21934-induced phenotypic responses, the potential involvement of 5-HT1A receptors in these antipsychotic-like effects was explored. The tests used were the following: MK-801-induced hyperactivity and 2,5-dimethoxy-4-iodoamphetamine (DOI)-induced head twitches in mice, for positive symptoms; MK-801-induced disruptions of social interactions for negative symptoms; and novel object recognition and spatial delayed alteration test for cognitive symptoms. The microdialysis studies in which the effect of Lu AF21934 on MK-801-induced dopamine and serotonin release was investigated. RESULTS: The effects caused by Lu AF2193 were inhibited by administration of the selective 5-HT1A receptor antagonist WAY100635 (0.1 mg/kg). That inhibition was observed across all models used. Moreover, the concomitant administration of sub-effective doses of Lu AF21934 and a sub-effective dose of the selective 5-HT1A receptor agonist tool compound (R)-(+)-8-hydroxy-DPAT hydrobromide (0.01 mg/kg) induced a clear antipsychotic-like effect in all the procedures used. Lu AF21934 (5 mg/kg) also inhibited MK-801-induced increase in dopamine and 5-HT release. CONCLUSIONS: The actions of Lu AF21934 are 5-HT1A receptor-dependent. Activation of the mGlu4 receptor may be a promising mechanism for the development of novel antipsychotic drugs, efficacious toward positive, negative, and cognitive symptoms.

The effect of caffeine on MDMA-induced hydroxyl radical production in the mouse striatum.

BACKGROUND: The psychostimulant 3,4-methylenedioxymethamphetamine (MDMA) with a strong addictive potential is widely used as a recreational drug. Neurotoxicity of MDMA is related with the generation of highly reactive free radicals. METHODS: MDMA was given in doses of 20 and 40mg/kg ip alone or in combination with caffeine (CAF) 10mg/kg ip. Extracellular concentration of hydroxyl radical was measured using microdialysis in freely moving mice and was assayed by HPLC with electrochemical detection. RESULTS: MDMA dose-dependently increased production of hydroxyl radical in the mouse striatum and its effect was reversed by caffeine. CONCLUSIONS: The data show that caffeine may have neuroprotective properties as it decreased oxidative stress induced by MDMA.

LPS-induced oxidative stress and inflammatory reaction in the rat striatum.

BACKGROUND: Inflammation-induced microglia activation and increased oxidative stress have been observed in neurodegenerative disorders, such as Parkinson's disease. The aim of our study was to determine the appropriate dose and route of LPS administration to study hydroxyl radical generation and extracellular level of dopamine (DA), glutamate (GLU) and adenosine (ADN) in the rat striatum as markers of DA neuron damage and glial cell activation. The effect of LPS administration on DA, DOPAC, HVA and hydroxyl radical tissue level was also examined. METHODS: LPS was given to rats in a single dose of 10 mg/kg ip, repeatedly for 5 days in a dose of 5 mg/kg ip and intrastriatally at doses 5, 20 and 40 µg/4 µl. The extracellular level of DA, hydroxyl radical, ADN and GLU were assayed in striatal dialysates using HPLC with electrochemical, fluorescence and VIS detection, respectively. RESULTS: A single ip LPS (10 mg/kg) administration increased hydroxyl radical production but did not affect extracellular DA, GLU and ADN level. Repeated ip LPS (5 × 5 mg/kg) treatment decreased extracellular level of DA, GLU, ADN and production of hydroxyl radical. LPS (5 and 10 µg) given intrastriatally increased hydroxyl radical production, extracellular GLU and ADN level from 0 to 180 min after administration, but did not influence DA level. LPS (5, 20 and 40 µg) decreased striatal DA and DOPAC content, but increased HVA and hydroxyl radical level 72 h after intrastriatal administration. CONCLUSIONS: Our data indicate that local intrastriatal LPS administration activates glial cells and increases production of free radicals and secretion of GLU and ADN in early phase of inflammation. The damage of DA neurons is observed 72 h after local LPS administration.

Effects of adenosine receptor antagonists on the in vivo LPS-induced inflammation model of Parkinson's disease.

The study shows effects of the nonselective adenosine A1/A2A receptor antagonist caffeine and the selective A2A receptor antagonist KW6002 on LPS-induced changes in the extracellular levels of dopamine (DA), glutamate, adenosine, hydroxyl radical, and A2A receptor density in the rat striatum. Intrastriatal LPS (10 µg) injection decreased extracellular level of DA and increased the level of adenosine, glutamate, and hydroxyl radical on the ipsilateral side 24 h after LPS administration. Caffeine (10 and 20 mg/kg i.p.) and KW6002 (1.5 and 3 mg/kg i.p.) given once daily for 6 days and on the 7th day 2 h before and 4 h after LPS injection reversed the LPS-induced changes in extracellular levels of DA, adenosine, glutamate, and hydroxyl radical production. Moreover, LPS-induced decrease in the striatal A2A receptor density was increased by caffeine and KW6002. In order to show the late LPS effect on oxidative damage of DA neurons, the contents of DA, DOPAC, HVA, and hydroxyl radical were determined 72 h after LPS (10 µg) administration into both striata. LPS decreased striatal and substantia nigra content of DA, DOPAC, and HVA while increased striatal but not nigral content of hydroxyl radical. Caffeine (20 mg/kg) and KW60002 (3 mg/kg) given once daily for 6 days and on the 7th day 2 h before and 4 h after intrastriatal injection of LPS normalized the content of DA and its metabolites in both brain regions as well as decreased LPS-induced increase in the striatal level of hydroxyl radical. In conclusion, our data demonstrated antioxidant effects of caffeine and KW6002 in the inflammatory model of PD.