O-GlcNAcylation in Ventral Tegmental Area Dopaminergic Neurons Regulates Motor Learning and the Response to Natural Reward / 神经科学通报·英文版

Protein O-GlcNAcylation is a post-translational modification that links environmental stimuli with changes in intracellular signal pathways, and its disturbance has been found in neurodegenerative diseases and metabolic disorders. However, its role in the mesolimbic dopamine (DA) system, especially in the ventral tegmental area (VTA), needs to be elucidated. Here, we found that injection of Thiamet G, an O-GlcNAcase (OGA) inhibitor, in the VTA and nucleus accumbens (NAc) of mice, facilitated neuronal O-GlcNAcylation and decreased the operant response to sucrose as well as the latency to fall in rotarod test. Mice with DAergic neuron-specific knockout of O-GlcNAc transferase (OGT) displayed severe metabolic abnormalities and died within 4-8 weeks after birth. Furthermore, mice specifically overexpressing OGT in DAergic neurons in the VTA had learning defects in the operant response to sucrose, and impaired motor learning in the rotarod test. Instead, overexpression of OGT in GABAergic neurons in the VTA had no effect on these behaviors. These results suggest that protein O-GlcNAcylation of DAergic neurons in the VTA plays an important role in regulating the response to natural reward and motor learning in mice.

Dopaminergic Neurons in the Ventral Tegmental-Prelimbic Pathway Promote the Emergence of Rats from Sevoflurane Anesthesia / 神经科学通报·英文版

Dopaminergic neurons in the ventral tegmental area (VTA) play an important role in cognition, emergence from anesthesia, reward, and aversion, and their projection to the cortex is a crucial part of the "bottom-up" ascending activating system. The prelimbic cortex (PrL) is one of the important projection regions of the VTA. However, the roles of dopaminergic neurons in the VTA and the VTADA-PrL pathway under sevoflurane anesthesia in rats remain unclear. In this study, we found that intraperitoneal injection and local microinjection of a dopamine D1 receptor agonist (Chloro-APB) into the PrL had an emergence-promoting effect on sevoflurane anesthesia in rats, while injection of a dopamine D1 receptor antagonist (SCH23390) deepened anesthesia. The results of chemogenetics combined with microinjection and optogenetics showed that activating the VTADA-PrL pathway prolonged the induction time and shortened the emergence time of anesthesia. These results demonstrate that the dopaminergic system in the VTA has an emergence-promoting effect and that the bottom-up VTADA-PrL pathway facilitates emergence from sevoflurane anesthesia.

Reinforcement omission effects in rats with bilateral lesions in the substantia nigra pars compacta and ventral tegmental area

Reinforcement omission effects (ROEs) are characterized by higher response rates after reinforcement omission than after reinforcement delivery. This pattern of behavior is interpreted in terms of motivational and attentional processes. Recent studies from our laboratory have shown that the amygdala, nucleus accumbens, and medial prefrontal cortex are involved in ROE modulation. Also, the literature has demonstrated a role of other areas such as substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) in processes related to surprising events, such as prediction error and presentation or omission of an event (exteroceptive stimulus and reinforcement). Since these structures send projections to areas related to ROE modulation such as the amygdala, nucleus accumbens, and prefrontal cortex, the objective of the present study was to determine whether the SNc and VTA also integrate the circuit involved in ROE modulation. Rats were trained on a fixed-interval 12 s with limited-hold 6 s signaled schedule of reinforcement (Pre-lesion training). After acquisition of stable performance, the rats received bilateral neurotoxic lesions of the SNc (Experiment 1) and VTA (Experiment 2). Following postoperative recovery, the rats were submitted to two refresher sessions (Post-lesion training). Subsequently, the training was changed from a 100 to a 50% schedule of reinforcement (Post-lesion testing). In both experiments, the results showed that there was no difference in performance between sham rats and rats with bilateral lesions of the SNc or the VTA.

A Group of Descending Glutamatergic Neurons Activated by Stress in Corticolimbic Regions Project to the Nucleus Accumbens

The nucleus accumbens (NAc) is the major component of the ventral striatum that regulates stress-induced depression. The NAc receives dopaminergic inputs from the ventral tegmental area (VTA), and the role of VTA-NAc neurons in stress response has been recently characterized. The NAc also receives glutamatergic inputs from various forebrain structures including the prelimbic cortex (PL), basolateral amygdala (BLA), and ventral hippocampus (vHIP), whereas the role of those glutamatergic afferents in stress response remains underscored. In the present study, we investigated the extent to which descending glutamatergic neurons activated by stress in the PL, BLA, and vHIP project to the NAc. To specifically label the input neurons into the NAc, fluorescent-tagged cholera toxin subunit B (CTB), which can be used as a retrograde neuronal tracer, was injected into the NAc. After two weeks, the mice were placed under restraint for 1 h. Subsequent histological analyses indicated that CTB-positive cells were detected in 170~680 cells/mm² in the PL, BLA, and vHIP, and those CTB-positive cells were mostly glutamatergic. In the PL, BLA, and vHIP regions analyzed, stress-induced c-Fos expression was found in 20~100 cells/mm². Among the CTB-positive cells, 2.6% in the PL, 4.2% in the BLA, and 1.1% in the vHIP were co-labeled by c-Fos, whereas among c-Fos-positive cells, 7.7% in the PL, 19.8% in the BLA, and 8.5% in the vHIP were co-labeled with CTB. These results suggest that the NAc receives a significant but differing proportion of glutamatergic inputs from the PL, BLA, and vHIP in stress response.

Expression of µ-Opioid Receptor in CA1 Hippocampal Astrocytes

µ-opioid receptor (MOR) is a class of opioid receptors with a high affinity for enkephalins and beta-endorphin. In hippocampus, activation of MOR is known to enhance the neuronal excitability of pyramidal neurons, which has been mainly attributed to a disinhibition of pyramidal neurons via activating Gαi subunit to suppress the presynaptic release of GABA in hippocampal interneurons. In contrast, the potential role of MOR in hippocampal astrocytes, the most abundant cell type in the brain, has remained unexplored. Here, we determine the cellular and subcellular distribution of MOR in different cell types of the hippocampus by utilizing MOR-mCherry mice and two different antibodies against MOR. Consistent with previous findings, we demonstrate that MOR expression in the CA1 pyramidal layer is co-localized with axon terminals from GABAergic inhibitory neurons but not with soma of pyramidal neurons. More importantly, we demonstrate that MOR is highly expressed in CA1 hippocampal astrocytes. The ultrastructural analysis further demonstrates that the astrocytic MOR is localized in soma and processes, but not in microdomains near synapses. Lastly, we demonstrate that astrocytes in ventral tegmental area and nucleus accumbens also express MOR. Our results provide the unprecedented evidence for the presence of MOR in astrocytes, implicating potential roles of astrocytic MOR in addictive behaviors.

How Leptin Controls the Drive to Eat

A complex set of brain based systems modulate feeding to maintain constant body weight. The adipose derived-hormone, leptin, plays a crucial role in this control by acting on diverse leptin receptor (LepRb)-expressing neurons in the hypothalamus and brainstem to modify behavior and metabolism. In addition to controlling energy expenditure and satiety, leptin controls motivation and the reward value of food by regulating two interconnected systems: hypocretin (HCRT) neurons and the mesolimbic dopamine (MLDA) system. Modest/acute decreases in leptin levels, as associated with mild caloric restriction, increase MLDA activity and overall food-seeking behavior; in contrast, severe starvation or complete leptin deficiency blunt MLDA activity, along with motivation and associated behaviors. Lateral hypothalamic (LHA) LepRb neurons project to dopamine (DA) neurons in the ventral tegmental area, where neurotensin (NT) release augments MLDA function; these LepRb(NT) cells also innervate HCRT neurons to control Hcrt expression and inhibit HCRT neurons. Ablation of LepRb in these cells abrogates the control of HCRT cells by leptin and decreases activity and MLDA function. We propose that this neural pathway regulates the MLDA, activity, and motivation in response to leptin and nutritional status.

Melanocortin 4 Receptor and Dopamine D2 Receptor Expression in Brain Areas Involved in Food Intake

BACKGROUND: The melanocortin 4 receptor (MC4R) is involved in the regulation of homeostatic energy balance by the hypothalamus. Recent reports showed that MC4R can also control the motivation for food in association with a brain reward system, such as dopamine. We investigated the expression levels of MC4R and the dopamine D2 receptor (D2R), which is known to be related to food rewards, in both the hypothalamus and brain regions involved in food rewards. METHODS: We examined the expression levels of D2R and MC4R by dual immunofluorescence histochemistry in hypothalamic regions and in the bed nucleus of the stria terminalis (BNST), the central amygdala, and the ventral tegmental area of transgenic mice expressing enhanced green fluorescent protein under the control of the D2R gene. RESULTS: In the hypothalamic area, significant coexpression of MC4R and D2R was observed in the arcuate nucleus. We observed a significant coexpression of D2R and MC4R in the BNST, which has been suggested to be an important site for food reward. CONCLUSION: We suggest that MC4R and D2R function in the hypothalamus for control of energy homeostasis and that within the brain regions related with rewards, such as the BNST, the melanocortin system works synergistically with dopamine for the integration of food motivation in the control of feeding behaviors.

Acamprosate-induced Extrapyramidal Symptoms in an Elderly Patient with Alcohol Dependence

Acamprosate reduces the craving for alcohol by decreasing glutamate activity and increasing gamma-aminobutyric acid (GABA) action in patients with alcohol dependence. Acamprosate has tolerable side effects that include diarrhea, headache, dizziness and pruritus. In this study, we report acamprosate-induced extrapyramidal symptoms in an elderly patient with no history of neurologic disease. Severe extrapyramidal symptoms developed two days after the administration of acamprosate and improved over one week after the acamprosate was stopped. Extrapyramidal symptoms are commonly associated with dopamine receptor antagonists. However, there have been several reports of extrapyramidal symptoms occurring with drugs targeting other systems, including GABA, glutamate and serotonin. Acamprosate may decrease dopamine levels in the ventral tegmental area mediated by glutamatergic action and thus cause extrapyramidal symptoms. We suggest that acamprosate carries the risk of causing extrapyramidal symptoms.

Expression of GAP-43 in midbrain ventral tegmental area of morphine withdrawal rats / 法医学杂志

OBJECTIVE@#To observe the protein expression of growth associated protein-43 (GAP-43) in midbrain ventral tegmental area in morphine withdrawal rats at different time, and to evaluate the effect of GAP-43 on morphine withdrawal memory.@*METHODS@#Rat models of morphine dependent 1 week, 2 weeks and 4 weeks were established by morphine hydrochloride intraperitoneal injection with increasing doses to establish natural withdrawal. The protein expression of GAP-43 in midbrain ventral tegmental area was observed by immunohistochemical staining and the results were analyzed by Image-Pro Plus 5.1 image analysis system.@*RESULTS@#With prolongation of dependent time, the expression of GAP-43 was decreased then increased in midbrain ventral tegmental area.@*CONCLUSION@#GAP-43 could play a role in morphine withdrawal memory in midbrain ventral tegmental area.

High-frequency stimulation on cell soma induces potentiation of intrinsic excitability in VTA dopaminergic neurons / 生理学报

Ventral tegmental area (VTA) is an important relay station of signal transmission in the reward system. The plasticity of VTA dopaminergic neurons directly influences actions of other regions of the reward system. Studies concerning the plasticity of VTA dopaminergic neurons focus mainly on synaptic plasticity, while much less attention has been given to the plasticity of intrinsic excitability of the neurons. The aim of the present study was to investigate the effect of high-frequency stimulation (HFS) on the plasticity of excitability of VTA neuron. Whole-cell patch-clamping was performed on VTA dopaminergic neurons in midbrain slices bathed with PTX, AP-5 and CNQX, and HFS was introduced to cell soma. The result showed that, after HFS induction the pharmacologically isolated neurons showed increased input resistance and firing frequency, as well as decreased rheobase. Meanwhile, the steady-state whole-cell current decreased, and the hyperpolarization-activated current (I(h)) decreased. These results suggest that HFS on soma induces a long-term potentiation of excitability in VTA dopaminergic neurons, and the underlying mechanism involves the changes of membrane current.

Chronic Administration of Baicalein Decreases Depression-Like Behavior Induced by Repeated Restraint Stress in Rats

Baicalein (BA), a plant-derived active flavonoid present in the root of Scutellaria baicalensis, has been widely used for the treatment of stress-related neuropsychiatric disorders including depression. Previous studies have demonstrated that repeated restraint stress disrupts the activity of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in depression. The behavioral and neurochemical basis of the BA effect on depression remain unclear. The present study used the forced swimming test (FST) and changes in brain neurotransmitter levels to confirm the impact of BA on repeated restraint stress-induced behavioral and neurochemical changes in rats. Male rats received 10, 20, or 40 mg/kg BA (i.p.) 30 min prior to daily exposure to repeated restraint stress (2 h/day) for 14 days. Activation of the HPA axis in response to repeated restraint stress was confirmed by measuring serum corticosterone levels and the expression of corticotrophin-releasing factor in the hypothalamus. Daily BA administration significantly decreased the duration of immobility in the FST, increased sucrose consumption, and restored the stress-related decreases in dopamine concentrations in the hippocampus to near normal levels. BA significantly inhibited the stress-induced decrease in neuronal tyrosine hydroxylase immunoreactivity in the ventral tegmental area and the expression of brain-derived neurotrophic factor (BDNF) mRNA in the hippocampus. Taken together, these findings indicate that administration of BA prior to the repeated restraint stress significantly improves helpless behaviors and depressive symptoms, possibly by preventing the decrease in dopamine and BDNF expression. Thus, BA may be a useful agent for the treatment or alleviation of the complex symptoms associated with depression.

Neurobiology, pharmacokinetics and pharmacodynamics of drug abuse

All drugs of abuse, like neural rewarding behaviors such as sex and eating, increase extra-cellular dopamine (DA) levels in the nucleus accumbens (NA), which is a part of the common reward mesolimbic pathway from the ventral tegmental area (VTA) to the NA. As addiction progresses from initial use to obsessive compulsive use, the neurobiology shifts from a DA-based behavioral system to a predominantly glutamate-based one, still relying on DA. A DA release in the prefrontal cortex (PFC) and amygdala in the relapse stimulates glutamate transmission between the PFC and amygdala and glutamate release in the pathway from the PFC to the NA core, constituting a "final common pathway" for drug-seeking behavior. Dysfunction of critical PFC structures results in drug craving and impaired decision making. Inhalation and smoking are the routes of administration that allow the most rapid delivery of drugs to the brain, while intravenous injection maximizes the bioavailability of a drug. The pharmacokinetic properties of a drug that dispose the user to increased self-administration include rapid absorption, rapid entry into the central nervous system, high bioavailability, short half-life, small volume of distribution, and high free drug clearance. The pharmacokinetic properties associated with drug dependence are a long half-life, low free drug clearance, and presence of the drug at high enough concentrations and for a sufficient time to permit tolerance to develop. Pharmacokinetics and pharmacodynamics play an important role in predicting the dependence and abuse potential of drugs.

Beyond Substance Addiction: Broadening the Concept of Addiction to Include Behavioral Addiction

No abstract available.

Etiology and Clinical Charateristics of Alcohol Use Disorder / 임상당뇨병

Alcohol use disorder (AUD) includes alcohol abuse and alcohol dependence. Since AUD is considered a bio-psycho-social disease, the etiology is multifactorial, including biological, psychological and social variables. Neurobiologically, addiction is related to the ventral tegmental area and nucleus accumbens, known as the "pleasure center," and an imbalance of various neurotransmitters such as dopamine, gamma-amino-butyric acid (GABA), and glutamate. Psychologically, chronic drinking is used as a means of self-medication for reducing tension and stress and overcoming anxiety and depression. Socially, the rate of alcoholism depends on the culture and social attitude toward drinking behaviors. Social learning and conditioning are the social causes of AUD. Common clinical features of AUD include physiological changes such as tolerance and withdrawal, and occupational and social dysfunction. AUD is also closely associated with physical illness, such as alcoholic liver disease, thyroid dysfunction, and cardiovascular diseases. Understanding the etiology and clinical features of AUD is the first step to managing patients with alcohol problems. Physicians should consider alcohol abuse as a serious alcohol-related disorder that impairs familial, social, and occupational functions as much as alcohol dependence.

Transcriptional Mechanisms of Drug Addiction

Regulation of gene expression is considered a plausible mechanism of drug addiction given the stability of behavioral abnormalities that define an addicted state. Numerous transcription factors, proteins that bind to regulatory regions of specific genes and thereby control levels of their expression, have been implicated in the addiction process over the past decade or two. Here we review the growing evidence for the role played by several prominent transcription factors, including a Fos family protein (DeltaFosB), cAMP response element binding protein (CREB), and nuclear factor kappa B (NFkappaB), among several others, in drug addiction. As will be seen, each factor displays very different regulation by drugs of abuse within the brain's reward circuitry, and in turn mediates distinct aspects of the addiction phenotype. Current efforts are geared toward understanding the range of target genes through which these transcription factors produce their functional effects and the underlying molecular mechanisms involved. This work promises to reveal fundamentally new insight into the molecular basis of addiction, which will contribute to improved diagnostic tests and therapeutics for addictive disorders.

Neurobiología de las adicciones y procesos de plasticidad involucrados / The Neurobiology of Addiction and the Plasticity Processes Involved

Las evidencias acumuladas en los últimos diez años, indican que las drogas de abuso pueden cooptar los mecanismos de plasticidad en circuitos cerebrales involucrados en las recompensas a reforzadores naturales (comida, bebida, sexo, etc.), resultando en una forma patológica pero poderosa, de memoria y aprendizaje. El circuito involucra esencialmente, el sistema dopaminérgico mesolímbico (area tegmental ventral (VTA), nucleus accumbens (NAcc) y estructuras límbicas asociadas). La plasticidad sináptica en las íreas involucradas incide particularmente en la abstinencia, la recurrencia, la reincidencia y la pérdida del autocontrol. La ínsula y en particular, la ínsula anterior derecha, participa en las percepciones de los estados emocionales corporales que generan las urgencias de consumo y las saliencias de incentivos corporales. Esto se refleja en los estudios imagenológicos funcionales y se confirma por la pérdida del hábito al consumo de tabaco en los casos de lesiones cerebrales en éstas áreas específicas.

Evidence gathered during the past ten years demonstrates that drugs of abuse may co-opt plasticity mechanisms in brain circuits involved in the rewards to natural reinforcements (food, drink, sex, etc.) which results in a pathological but powerful form of memory and learning. The circuit basically involves the mesolimbic dopamine system (ventral tegmental area (VTA), the nucleus accumbens (NAcc) and associated limbic structures). The synaptic plasticity in the areas involved particularly impacts on abstinence, recurrence, recidivism and the loss of self-control. The insula, and the right anterior insula in particular, plays a role in the perceptions of the emotional states of the body that trigger the craving for consumption and the salience of body incentives. This is depicted in functional imaging studies and is demonstrated by the break of the habit of smoking in cases of brain injuries in these specific areas.

The influence of L-glutamate and carbachol on burst firing of dopaminergic neurons in ventral tegmental area / 生理学报

Burst firing of dopaminergic neurons in ventral tegmental area (VTA) induces a large transient increase in synaptic dopamine (DA) release and thus is considered the reward-related signal. But the mechanisms of burst generation of dopaminergic neuron still remain unclear. This experiment investigated the burst firing of VTA dopaminergic neurons in rat midbrain slices perfused with carbachol and L-glutamate individually or simultaneously to understand the neurotransmitter mechanism underlying burst generation. The results showed that bath application of carbachol (10 μmol/L) and pulse application of L-glutamate (3 mmol/L) both induced burst firing in dopaminergic neuron. Co-application of carbachol and L-glutamate induced burst firing in VTA dopaminergic cells which couldn't be induced to burst by the two chemicals separately. The result indicates that carbachol and L-glutamate co-regulate burst firing of dopaminergic neuron.

Sistemas de motivación y su impacto en la resiliencia: mecanismos neurobiológicos y moleculares implicados / Reward systems and their impact in resilience: neurobiological and molecular mechanisms implicated

La resiliencia en un individuo tiene relación con el potencial de permanecer psicológicamente sano a pesar de estar sometido a situaciones de alto riesgo psicosocial.En esta revisión se aborda el complejo fenotipo de la resiliencia bajo el punto de vista de los sistemas de motivación y del circuito dopaminérgico que involucra al área ventral tegmental (VTA) y al núcleo accumbens (NAc) junto con la participación fundamental del neuropéptido factor neurotrófico derivado del cerebro (BDNF). Lo esencial con respecto a este neuropéptido es que un incremento de su señal en el NAc, producto de un aumento en la descarga neuronal del VTA, promueve un fenotipo susceptible (vulnerable) al stress social, este aumento del BDNF no ocurre en el NAc de los fenotipos resilientes. Otro hecho interesante que se menciona en este artículo, es la existencia de un polimorfismo que ocurre en humanos que tiene relación con el gen del BDNF (G196A, Val66 Met), que impide la liberación de este factor neurotrófico. La presencia de este polimorfismo evidencia, en cierta forma, la existencia de una variabilidad interindividual en la respuesta frente al stress social, concepto que nos acerca a una mirada evolutiva que también se pretende dar en esta revisión. La participación de los sistemas de recompensa en el desarrollo de la resiliencia implica un aspecto que tiene el potencial de continuar estudiándose y contribuir en la aplicación de nuevas estrategias de intervención en salud mental de poblaciones expuestas a condiciones de alto riesgo psicosocial.

Resilience in an individual has relation with the potential to keep psychologically healthy despite of high psychosocial risk situations. In this review, the complex resilience phenotype is analyzed under a viewpoint of the reward systems and the dopaminergic pathways that involves the ventral tegmental area (VTA) and the nucleusaccumbens (NAc), also with the fundamental participation of the brain derived neurotrophic factor (BDNF). An increasing signalling of this neuropeptide in the NAc, as a result of an enhanced neuronal firing from the VTA, produces a susceptible phenotype to social defeat instead of a resilient phenotype that does not show this BDNF increase. Another important issue is the existence of the BDNF gene polymorphism (G196A, Val66 Met) that occurs in humans. This polymorphism inhibits the release of this neuropeptide. This fact explains, in some way, an interindividual variability in the response to social defeat wish brings to us an evolutionary look that this review also pretends to give. The participation of the reward systems in developing resilience is a topic that has the potential to continue studying and by this way contribute to the application of new strategies of intervention in mental health of people exposed to high psychosocial risk conditions.

[Effects of ascorbic acid on the amplitude of ventral tegmental area field action potential in morphine-exposed rats [an electrophysiology study]]

Evidences have indicated that the Ventral Tegmental Area [VTA] is the major source of dopamine [DA] neurons projecting to cortical and limbic regions involved in cognitive and motivational aspects of addiction. Also, studies have indicated that the Ascorbic acid [vitamin C] can reduce the dependency symptoms of opioids such as morphine via effect of activity on dopaminergic neuron in VTA. For this reason, the aim of this study was to assess the effects of ascorbic acid on the amplitude of Ventral Tegmental Area field action potential in morphine-exposed rats. Forty male Wistar's rats were used in this experimental study conducted at Yasuj University of Medical Sciences in 2010. Animals were randomly divided into four groups after electrode implantation and recovery period: 1. No- Vit C and No-Addicted group [nVitC.nA] 2. Vit C and No-Addicted group [VitC.nA] 3. No- Vit C and Addicted group [nVitCA] 4.Vit C and Addicted [VitC.A], The Vit C groups received 500 mg/kg of Vit C during 20 days. For addicted groups morphine was administrated once daily for 20 days. In the 20[th] day, the field potential recording was accomplished. Two-way ANOVA was used for data analysis followed by the Tukey test for post hoc analysis. Results were considered significant at P<0.05. This study shows the exposure to morphine declined the power of Delta and Beta bands [p<0.05] and Vit C solely enhance power of Theta and Beta [p<0.05, p<0.001] in VTA nuclei. Furthermore, Vit C could alter power of some bands which were affected by morphine. Therefore, it seems that Vit C has an increasing effects on them [p<0.05]. Although the effect of Vit C on power of the VTA bands is not well known, but it is supposed that this phenomenon can be related to alteration in activity of dopaminergic neuron in the brain

effects of ascorbic acid injection in to locus ceruleus and ventral tegmental area and PGi on morphine withdrawal signs in rats

Recent studies indicate that the glutamatergic and dopaminergic systems are involved in morphine withdrawal syndrome. Ascorbic acid [ascorbate] is an antioxidant vitamin released from glutamatergic neurons and modulates the synaptic action of dopamine and glutamate in the locus ceruleus, ventral tegmental area and PGi as well as behavior. To determine the effects of ascorbic acid injection into locus ceruleus, ventral tegmental area and PGi on morphine withdrawal signs in rats [MWS]. This was an experimental study in which a total of 80 male rats [250-300gr] divided into two were tested. The first group marked as control received 3% sucrose in tap water [n=10] and the second group [dependent group] received morphine and 3% sucrose in tap water [0.1, 0.2, 0.3, 0.4mg/ml each for 48h, and 0.4mg/ml for the remaining days up to day 21]. The latter was further divided into 7 subgroups as follows: [1] morphine group; [2, 3, and 4] sham operated groups which were surgically implanted with cannula at the locus ceruleus [LC], ventral tegmental area [VTA], and PGi; [5, 6, 7] morphine-ascorbic acid groups injected with AA [8 microg/microl] into LC, VTA, and PGi at day 21 and 5 min before naloxone administration. At the end of the training day, all groups received naloxone [2mg/kg I.P] and MWS was studied for 30 minute. Our results showed that the injection of ascorbate into LC and PGi caused a higher decrease in morphine withdrawal syndrome signs compared to VTA. Glutamatergic system is more effective than dopaminergic system in attenuation of MWS by acute injection of ascorbate