Effect of drug-induced ascorbic acid release in the striatum and the nucleus accumbens in hippocampus-lesioned rats

The Association of Redox Regulatory Drug Target Genes with Psychiatric Disorders: A Mendelian Randomization Study

Redox regulatory drug (RRD) targets may be considered potential novel drug targets of psychosis due to the fact that the brain is highly susceptible to oxidative stress imbalance. The aim of the present study is to identify potential associations between RRD targets' perturbation and the risk of psychoses; to achieve this, Mendelian randomization analyses were conducted. The expression quantitative trait loci (eQTL) and protein QTL data were used to derive the genetic instrumental variables. We obtained the latest summary data of genome-wide association studies on seven psychoses as outcomes, including schizophrenia (SCZ), bipolar disorder (BD), major depressive disorder (MDD), attention-deficit/hyperactivity disorder, autism, obsessive-compulsive disorder and anorexia nervosa. In total, 95 unique targets were included in the eQTL panel, and 48 targets in the pQTL one. Genetic variations in the vitamin C target (OGFOD2, OR = 0.784, p = 2.14 × 10-7) and melatonin target (RORB, OR = 1.263, p = 8.80 × 10-9) were significantly related to the risk of SCZ. Genetic variation in the vitamin E (PRKCB, OR = 0.248, p = 1.24 × 10-5) target was related to an increased risk of BD. Genetic variation in the vitamin C target (P4HTM: cerebellum, OR = 1.071, p = 4.64 × 10-7; cerebellar hemisphere, OR = 1.092, p = 1.98 × 10-6) was related to an increased risk of MDD. Cognitive function mediated the effects on causal associations. In conclusion, this study provides supportive evidence for a causal association between RRD targets and risk of SCZ, BD or MDD, which were partially mediated by cognition.

Functional role of ascorbic acid in the central nervous system: a focus on neurogenic and synaptogenic processes

Ascorbic acid, a water-soluble vitamin, is highly concentrated in the brain and participates in neuronal modulation and regulation of central nervous system (CNS) homeostasis. Ascorbic acid has emerged as a neuroprotective compound against neurotoxicants and neurodegenerative diseases, including Alzheimer's disease, multiple sclerosis and amyotrophic lateral sclerosis. Moreover, it improves behavioral and biochemical alterations in psychiatric disorders, including schizophrenia, anxiety, major depressive disorder, and bipolar disorder. Some recent studies have advanced the knowledge on the mechanisms associated with the preventive and therapeutic effects of ascorbic acid by showing that they are linked to improved neurogenesis and synaptic plasticity. This review shows that ascorbic acid has the potential to regulate positively stem cell generation and proliferation. Moreover, it improves neuronal differentiation of precursors cells, promotes adult hippocampal neurogenesis, and has synaptogenic effects that are possibly linked to its protective or therapeutic effects in the brain.

Function of complement factor H and imaging of small molecules by MALDI-MSI in a methamphetamine behavioral sensitization model

BACKGROUND

At present, the harm of new-type drug, methamphetamine (METH), has gradually exceeded that of the traditional opioid drugs, and METH abuse has become a serious public health and social problem. In our previous study, complement factor H (CFH) was found to be upregulated in the sera of METH-addicted patients and rats and in certain brain regions in the rats.

METHODS

We used ELISA and immunofluorescence to confirm the changes in CFH in the serum and hippocampus of a METH behavioral sensitization mouse model, and C1q expression was also detected by immunofluorescence in the hippocampus. We aimed to elucidate the involvement of CFH and C1q in the mechanism of METH addiction. We also detected the distribution of various small molecules by matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) in select brain regions: the nucleus accumbens, the hippocampus and the ventral tegmental area.

RESULTS

The expression of CFH was upregulated in the serum and hippocampus of METH behavioral sensitization model mice, consistent with our previous research on conditioned place preference rats. In contrast, C1q decreased dramatically in the mossy fibers of the hippocampus. The results of small-molecule imaging by MALDI-MSI showed that the levels of K⁺, antioxidants, neurotransmitters, and ATP metabolism-related molecules were altered in different regions.

CONCLUSIONS

These results indicate the involvement of the complement system in the mechanism of METH addiction and validate the presence of oxidative stress, energy metabolism changes during addiction. This suggests the utility of further investigation into the above aspects.

Ascorbic Acid to Manage Psychiatric Disorders

Ascorbate has critical roles in the central nervous system (CNS); it is a neuromodulator of glutamatergic, cholinergic, dopaminergic, and γ-aminobutyric acid (GABA)-ergic neurotransmission, provides support and structure to neurons, and participates in processes such as differentiation, maturation, and survival of neurons. Over the past decade, antioxidant properties of ascorbate have been extensively characterized and now it is known that this compound is highly concentrated in the brain and neuroendocrine tissues. All this information raised the hypothesis that ascorbate may be involved in neurological disorders. Indeed, the biological mechanisms of ascorbate in health and disease and its involvement in homeostasis of the CNS have been the subject of extensive research. In particular, evidence for an association of this vitamin with schizophrenia, major depressive disorder, and bipolar disorder has been provided. Considering that conventional pharmacotherapy for the treatment of these neuropathologies has important limitations, this review aims to explore basic and human studies that implicate ascorbic acid as a potential therapeutic strategy. Possible mechanisms involved in the beneficial effects of ascorbic acid for the management of psychiatric disorders are also discussed.

Regional variations of antioxidant capacity and oxidative stress responses in HIV-1 transgenic rats with and without methamphetamine administration

HIV infection and methamphetamine (Meth) abuse both may lead to oxidative stress. This study used HIV-1 transgenic (HIV-1Tg) rats to investigate the independent and combined effects of HIV viral protein expression and low dose repeated Meth exposure on the glutathione (GSH)-centered antioxidant system and oxidative stress in the brain. Total GSH content, gene expression and/or enzymatic activities of glutamylcysteine synthetase (GCS), gamma-glutamyltransferase (GGT), glutathione reductase (GR), glutathione peroxidase (GPx), glutaredoxin (Glrx), and glutathione-s-transferase (GST) were measured. The protein expression of cystine transporter (xCT) and oxidative stress marker 4-hydroxynonenal (HNE) were also analyzed. Brain regions studied include thalamus, frontal and remainder cortex, striatum, cerebellum and hippocampus. HIV-1Tg rats and Meth exposure showed highly regional specific responses. In the F344 rats, the thalamus had the highest baseline GSH concentration and potentially higher GSH recycle rate. HIV-1Tg rats showed strong transcriptional responses to GSH depletion in the thalamus. Both HIV-1Tg and Meth resulted in decreased GR activity in thalamus, and decreased Glrx activity in frontal cortex. However, the increased GR and Glrx activities synergized with increased GSH concentration, which might have partially prevented Meth-induced oxidative stress in striatum. Interactive effects between Meth and HIV-1Tg were observed in thalamus on the activities of GCS and GGT, and in thalamus and frontal cortex on Glrx activity and xCT protein expression. Findings suggest that HIV viral protein and low dose repeated Meth exposure have separate and combined effects on the brain's antioxidant capacity and the oxidative stress response that are regional specific.

NMDA receptors in the medial prefrontal cortex and the dorsal hippocampus regulate methamphetamine-induced hyperactivity and extracellular amino acid release in mice

The medial prefrontal cortex (mPFC) and the dorsal hippocampus (DHC) play significant roles in stimulant-induced neurobehavioral effects. Methamphetamine (MAP)-induced hyperactivity has been reported to be involved in the regulation of the glutamatergic system. The present study examined whether the glutamatergic and GABAergic systems in the mPFC and DHC were involved in MAP-induced hyperactivity in mice. A combined kainic acid (KA) or N-methyl-d-aspartate (NMDA) lesion and microdialysis technique targeting both the mPFC and DHC were used. The results showed that both KA- and NMDA-induced lesions of the mPFC facilitated MAP-induced hyperactivity, while neither KA- nor NMDA-induced lesions of the DHC had a similar effect. MAP increased the extracellular glutamate (Glu) levels in the mPFC and reduced Glu levels in the DHC. GABA levels in both of these regions were reduced. A KA or NMDA lesion of the mPFC inhibited the Glu reduction in the DHC, and the same lesion of the DHC inhibited the Glu increase in the mPFC induced by MAP. A NMDA lesion of the mPFC blocked GABA reduction in the DHC, but a lesion of DHC enhanced the GABA decrease in the mPFC induced by MAP. Furthermore, a NMDA lesion of DHC increased the vesicular glutamate transporter-2 (VGLUT2) expression in the mPFC following MAP-administration. These findings indicate that glutamatergic as well as GABAergic systems in these two regions are involved in MAP-induced hyperactivity. Moreover, there may be an inhibitory role in these two regions, especially mediated by NMDA receptors, in MAP-induced abnormal behavior and neurotransmission responses.

Development and characterization of an implantable biosensor for telemetric monitoring of ethanol in the brain of freely moving rats

Ethanol is one of the most widespread psychotropic agents in western society. While its psychoactive effects are mainly associated with GABAergic and glutamatergic systems, the positive reinforcing properties of ethanol are related to activation of mesolimbic dopaminergic pathways resulting in a release of dopamine in the nucleus accumbens. Given these neurobiological implications, the detection of ethanol in brain extracellular fluid (ECF) is of great importance. In this study, we describe the development and characterization of an implantable biosensor for the amperometric detection of brain ethanol in real time. Ten different designs were characterized in vitro in terms of Michaelis-Menten kinetics (V(MAX) and K(M)), sensitivity (linear region slope, limit of detection (LOD), and limit of quantification (LOQ)), and electroactive interference blocking. The same parameters were monitored in selected designs up to 28 days after fabrication in order to quantify their stability. Finally, the best performing biosensor design was selected for implantation in the nucleus accumbens and coupled with a previously developed telemetric device for the real-time monitoring of ethanol in freely moving, untethered rats. Ethanol was then administered systemically to animals, either alone or in combination with ranitidine (an alcohol dehydrogenase inhibitor) while the biosensor signal was continuously recorded. The implanted biosensor, integrated in the low-cost telemetry system, was demonstrated to be a reliable device for the short-time monitoring of exogenous ethanol in brain ECF and represents a new generation of analytical tools for studying ethanol toxicokinetics and the effect of drugs on brain ethanol levels.

Lesions of nucleus accumbens affect morphine-induced release of ascorbic acid and GABA but not of glutamate in rats

Our previous studies have shown that local perfusion of morphine causes an increase of extracellular ascorbic acid (AA) levels in nucleus accumbens (NAc) of freely moving rats. Lines of evidence showed that glutamatergic and GABAergic were associated with morphine-induced effects on the neurotransmission of the brain, especially on the release of AA. In the present study, the effects of morphine on the release of extracellular AA, γ-aminobutyric acid (GABA) and glutamate (Glu) in the NAc following bilateral NAc lesions induced by kainic acid (KA) were studied by using the microdialysis technique, coupled to high performance liquid chromatography with electrochemical detection (HPLC-ECD) and fluorescent detection (HPLC-FD). The results showed that local perfusion of morphine (100 µM, 1 mM) in NAc dose-dependently increased AA and GABA release, while attenuated Glu release in the NAc. Naloxone (0.4 mM) pretreated by local perfusion to the NAc, significantly blocked the effects of morphine. After NAc lesion by KA (1 µg), morphine-induced increase in AA and GABA were markedly eliminated, while decrease in Glu was not affected. The loss effect of morphine on AA and GABA release after KA lesion could be recovered by GABA agonist, musimol. These results indicate that morphine-induced AA release may be mediated at least by µ-opioid receptor. Moreover, this effect of morphine possibly depend less on the glutamatergic afferents, but more on the GABAergic circuits within this nucleus. Finally, AA release induced by local perfusion of morphine may be GABA-receptor mediated and synaptically localized in the NAc.

GABAA receptors in VTA mediate the morphine-induced release of ascorbic acid in rat nucleus accumbens

Local perfusion of morphine produces increased levels of extracellular ascorbic acid (AA) in the nucleus accumbens (NAc) of freely moving rats. However, the pathways that regulate morphine-induced AA release in the NAc are unclear. In the present study, we used high performance liquid chromatography with electrochemical detection (HPLC-ECD) to examine the effects of intra-ventral tegmental area (VTA) administration of a GABA(A) agonist and antagonist on morphine-induced increases in AA of the NAc. Also, using high performance liquid chromatography with fluorescent detection (HPLC-FD) and HPLC-ECD, the releases of γ-aminobutyric acid (GABA) and dopamine (DA) in the NAc induced by intra-VTA administration of a GABA(A) agonist and antagonist were also investigated. The results obtained showed that morphine (1 mM), locally perfused into the NAc, significantly increased AA release in the NAc and also GABA release. Intra-VTA infusion of bicuculline (150 ng/rat), a GABA receptor antagonist, not only abolished the enhanced extracellular AA and GABA levels produced by local perfusion of morphine but also decreased the basal release of extracellular GABA and increased the basal release of extracellular DA in the NAc. Muscimol (100 ng/rat), a GABA receptor agonist, affected the basal release of GABA and DA, but not the basal AA levels, or the morphine-induced changes in AA and GABA levels. These findings suggest that the GABA(A) receptors in the VTA play an important role in the modulation of morphine-induced AA release in the NAc, and the effect of morphine on AA release in the NAc is partially regulated by the GABA(A) receptor-mediated action of DA afferents from the VTA.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).