Search Results (94)

Background/Objectives: Contextual memory associated with methamphetamine (METH) use contributes to relapse and persistence of addiction. Angiotensin II type 1 receptor (AT1R) signaling has been implicated in drug reinforcement. LCZ696, a clinically used combination of sacubitril (a neprilysin inhibitor) and valsartan (an AT1R antagonist), may interfere with METH-associated memory through the modulation of dopaminergic pathways. Methods: Male C57BL/6J mice were tested in a conditioned place preference (CPP) paradigm to assess the effects of LCZ696, sacubitril (AHU377), and valsartan on METH-induced memory expression and reinstatement. Synaptic plasticity in the nucleus accumbens (NAc) was examined by assessing the levels of synaptophysin (Syp) and postsynaptic density protein 95 (Psd95), as well as dendritic spine density. Dopaminergic signaling in the ventral tegmental area (VTA) was evaluated via ELISA, Western blotting, and chromatin immunoprecipitation (ChIP), targeting cAMP response element-binding protein (Creb) binding to the tyrosine hydroxylase (Th) promoter. To further assess the role of Th, an adeno-associated virus (AAV9) carrying a CRISPR-Cas9-based sgRNA targeting Th (AAV9-Th-sgRNA) was microinjected into the VTA. Results: LCZ696 and valsartan significantly reduced METH-induced CPP and reinstatement. LCZ696 reversed METH-induced synaptic and dopaminergic alterations and suppressed Creb-mediated Th transcription. Th knockdown attenuated both CPP acquisition and relapse. Conclusions: LCZ696 disrupts METH-associated contextual memory by modulating dopaminergic signaling and Creb-dependent Th expression, supporting its potential as a treatment for METH use disorder. Full article

The lateral hypothalamic area (LHA) serves as a central integrative hub for the regulation of energy homeostasis and motivational behaviors, including feeding and arousal. Recent advances in single-cell transcriptomics have revealed remarkable molecular heterogeneity within the LHA, identifying more than 30 distinct neuronal subtypes, such as GABAergic (LHA^Vgat), glutamatergic (LHA^Vglut2), orexin, melanin-concentrating hormone (MCH), and leptin receptor-expressing (LHA^Lepr) neurons. These neuronal populations sense peripheral metabolic signals—such as leptin, insulin, and glucose—both directly and indirectly, and they coordinate appropriate physiological and behavioral responses through local circuits and reciprocal connections with other hypothalamic nuclei. Furthermore, the LHA interfaces with extrahypothalamic regions, including the ventral tegmental area (VTA), nucleus accumbens (NAc), and lateral habenula (LHb), thereby linking metabolic state to reward processing and behavioral prioritization. In this review, we summarize and integrate recent molecular and functional findings to present a comprehensive view of the LHA as a dynamic, multifunctional center in the central regulation of metabolism. A deeper understanding of these mechanisms may offer new therapeutic avenues for addressing obesity and related metabolic disorders. Full article

The neurobiology of chronic pain is complex and multifaceted, intertwining with the mesocorticolimbic system to regulate the behavioral and perceptional response to adverse stimuli. Specifically, the ventral tegmental area (VTA), the dopaminergic hub of the reward pathways located deep within the midbrain, is crucial for regulating the release of dopamine (DA) throughout the central nervous system (CNS). To better understand the nuances among chronic pain, VTA response, and therapeutics, implementing progressive approaches for mapping and visualizing the deep brain in real time during nociceptive stimulation is crucial. In this study, we utilize a fluorescence imaging platform with a genetically encoded calcium indicator (GCaMP6s) to directly visualize activity in the VTA during acute nociceptive stimulation in both healthy adult mice and adult mice with partial nerve ligation (PNL)-induced neuropathic pain. We also investigate the visualization of the analgesic properties of morphine. Deep brain imaging using our self-fabricated µ-complementary metal–oxide–semiconductor (CMOS) imaging device allows the tracking of the VTA’s response to adverse stimuli. Our findings show that nociceptive stimulation is associated with a reduction in VTA fluorescence activity, supporting the potential of this platform for visualizing pain-related responses in the central nervous system. Additionally, treatment with morphine significantly reduces the neuronal response caused by mechanical stimuli and is observable using the CMOS imaging platform, demonstrating a novel way to potentially assess and treat neuropathic pain. Full article

The generalization of fear memories is an adaptive neurobiological process that promotes survival in complex and dynamic environments. While generalization has adaptive value, fear generalization is maladaptive and is a significant feature of stress-related disorders such as post-traumatic stress disorder (PTSD). The dopamine system plays a crucial role in both reward- and fear-related processes; however, the contribution of dopamine D3 receptors (D3Rs) to fear generalization in intense foot-shock models remains unclear. In this study, we administered a highly selective D3R antagonist, YQA14 (1 μg/0.2 μL/side), in the ventral tegmental area (VTA), which significantly inhibited fear generalization in novel contexts within foot-shock models. This effect was mediated by reducing the neuronal activity in the basolateral amygdala (BLA). These findings enhance our understanding of the neurobiology of generalization, which is essential from a translational perspective and has broad implications for treating generalized fear disorders. Full article

Background: A rat robot can be constructed by electrically stimulating specific brain regions to control rat locomotion and behavior. The rat robot makes full use of the rat’s motor function and energy supply and has significant advantages in motor flexibility, environmental adaptability, and covertness. It can be widely used in disaster search and rescue, terrain survey, anti-terrorism, and explosion-proof tasks. However, the motor control of existing rat robots mainly relies on the virtual whisker touch produced by the electrical stimulation of the barrel area of the somatosensory cortex and the virtual reward generated by the electrical stimulation of the medial forebrain bundle. The methods requires substantial experimental training to encourage the animals to match the virtual sensation with the motor behavior. However, the conditioned reflexes acquired by the animals will gradually disappear after a period of time at the end of the experiments, which will lead to a decrease in the stability of the motor control system. Methods: In this study, we developed a new method to gain control of inclined movement in rats by the electrical stimulation of the ventral tegmental area (VTA) of the midbrain and motor control of steering in rats by the electrical stimulation of nigrostriatal (NS) pathway. Results: The results showed that the electrical stimulation of the rat VTA could induce stable inclined movement in rats and that the neuromodulatory effect significantly correlated with the electrical stimulation parameters. In addition, the electrical stimulation of the NS pathway was able to directly and stably induce the steering movements of the head and trunk to the contralateral side of the stimulated side of the rat. Conclusions: These findings are of great importance for the motor control of rat robots, especially in the field environment with many slopes. In addition, the rat robot constructed based on this method does not need pre-training while ensuring reliability, which greatly improves the preparation efficiency and has certain practical application value. Full article

Nicotine addiction is a serious global public health problem, so there is an urgent necessity to develop novel effective smoking cessation treatments with fewer adverse effects. Spontaneous behavioral sensitization induced by repeated intermittent exposure to the addictive substance represents a classical animal model of addiction research. A significant contributor to nicotine addiction is its interaction with α6β2* nAChRs located on midbrain dopaminergic neurons, which leads to an increase in dopamine (DA) release. α-Conotoxin (α-CTx) TxIB is a novel potent antagonist of the α6/α3β2β3* nAChRs, with an IC50 value of 28.4 nM developed by our group. In this study, we aimed to investigate the effectiveness of α-CTx TxIB in countering nicotine-induced behavioral sensitization and moderating the impact of nicotine on dopamine accumulation in the midbrain. Our results demonstrated that repeated nicotine administration remarkably elevated the locomotor activity of mice, including the number of entries, average speed, and total distance traveled, which could be effectively attenuated by α-CTx TxIB intervention in a dose-dependent manner (1 nmol and 5 nmol TxIB per mouse). Furthermore, 5 nmol α-CTx TxIB significantly reduced the nicotine-elevated DA and norepinephrine (NE) levels in the ventral tegmental area (VTA) and nucleus accumbens (NAc) of mice. 5 nmol α-CTx TxIB also markedly decreased the expression of critical proteins such as the dopamine transporter (DAT), N-methyl-D-aspartic acid receptor (NMDAR), and c-Fos in the NAc and prefrontal cortex (PFC) of the nicotine-exposed mice. This research provided the first compelling evidence that α-CTx TxIB attenuated nicotine-induced locomotor sensitization and inhibited the nicotine-induced dopamine elevation in mice. These results open up new avenues for exploring the therapeutic potential of α-CTx TxIB in the treatment of nicotine addiction. Full article

Binge eating disorder (BED) is characterized by the rapid overconsumption of palatable food in a short amount of time, often leading to obesity. The endocannabinoid system (ECS), a system involved in palatable food intake, is highly expressed in reward-related brain regions and is involved in both obesity and BED. This study investigated differences in ECS expression between these conditions using male Wistar rats exposed to specific regimen over six weeks: a non-access group (NA) with a standard diet, a continuous access group (CA) with free-choice high-fat high-sugar (fcHFHS) diet modeling obesity, and an intermittent access group (IA) with intermittent fcHFHS access modeling BED. Food intake was measured, and brain tissues from the nucleus accumbens (NAc), dorsal striatum (DS), ventral tegmental area (VTA), and rostromedial tegmental nucleus (RMTg) were analyzed for ECS expression using qPCR and mass spectrometry. We identified differential ECS expression across palatable food access groups, with variations depending on the brain region (striatal or mesencephalic). Correlation analyses revealed ECS dysregulations dependent on the type (fat or sucrose) and quantity of palatable food consumed. Comparative network analysis revealed co-regulation patterns of ECS-related genes with specific signatures associated with each eating pattern, highlighting RMTg as a key region for future research in eating behavior. Full article

Astrocytes from different brain regions respond with Ca²⁺ elevations to the catecholamine norepinephrine (NE). However, whether this noradrenergic-mediated signaling is present in astrocytes from the ventral tegmental area (VTA), a dopaminergic circuit receiving noradrenergic inputs, has not yet been investigated. To fill in this gap, we applied a pharmacological approach along with two-photon microscopy and an AAV strategy to express a genetically encoded calcium indicator in VTA astrocytes. We found that VTA astrocytes from both female and male young adult mice showed a strong Ca²⁺ response to NE at both soma and processes. Our results revealed that Gq-coupled α1 adrenergic receptors, which elicit the production of IP3, are the main mediators of the astrocyte response. In mice lacking the IP3 receptor type-2 (IP3R2^−/− mice), we found that the astrocyte response to NE, even if reduced, is still present. We also found that in IP3R2^−/− astrocytes, the residual Ca²⁺ elevations elicited by NE depend on the release of Ca²⁺ from the endoplasmic reticulum, through IP3Rs different from IP3R2. In conclusion, our results reveal VTA astrocytes as novel targets of the noradrenergic signaling, opening to new interpretations of the cellular and molecular mechanisms that mediate the NE effects in the VTA. Full article

Amphetamine abuse is a global health epidemic that is difficult to treat due to individual differences in response to environmental factors, including stress reactivity and anxiety levels, as well as individual neuronal differences, which may result in increased/decreased vulnerability to addiction. In the present study, we investigated whether the Wistar rats behavioral traits of high (HR) and low (LR) locomotor activity to novelty influence motivational behavior (induced feeding model; iFR by electrical stimulation of the ventral tegmental area; Es-VTA) supported by amphetamine injection into the nucleus accumbens shell (AcbSh) (HR_Amph, n = 5; LR_Amph, n = 5). A correlation was found between the novelty test’s locomotor activity score and the frequency threshold percentage change (p < 0.001, Rs = −0.867). In HR_Amph, there was a shortening (−24.16%), while in LR_Amph, there was a lengthening (+51.84%) of iFR latency. Immunofluorescence studies showed differential neuronal density (activity of tyrosine hydroxylase, choline acetyltransferase, and cFos protein) in the selected brain structures in HR_Amph and LR_Amph animals as well as in comparison to a control group (HR_ACSF, n = 5; LR_ACSF, n = 5). These results contribute to expanding the state of knowledge of the behavioral and neuronal propensity to take drug abuse. Full article

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. However, the core biology of the disorder that leads to the hypofunctioning of the cerebral dopaminergic network requires further elucidation. We investigated midbrain synaptic changes in male rats exposed to repeated hypoxia during the equivalent of extreme prematurity, which is a new animal model of the hyperactive/impulsive presentation of ADHD. We used a novel combination of a lentiviral vector, peroxidase-immunonanogold double-labelling, three-dimensional serial section transmission electron microscopy and stereological techniques to investigate the synapses formed between GABAergic axons of the rostromedial tegmental nucleus (RMTg) and dopaminergic neurons of the posterior ventral tegmental area (pVTA). This is a key site that sends extensive dopaminergic projections to the forebrain. We also compared the results to our previous study on a schizophrenia risk factor that produces cerebral hyperdopaminergia. In total, 117 reconstructed synapses were compared. Repeated hypoxic rats had a significantly thicker (22%) and longer (18%) postsynaptic density at RMTg GABAergic-pVTA dopaminergic synapses compared to their controls. These results were opposite to those previously observed in rats exposed to a schizophrenia risk factor. These findings for repeated hypoxic rats suggest that the enhanced inhibition of pVTA dopaminergic neurons may contribute to hypodopaminergia in ADHD motor hyperactivity. Synaptic triads, a key component of pVTA circuitry, were not detected in repeated hypoxic rats, indicating a marked deficit. The current knowledge may guide development in males of novel, site-specific ADHD drugs, which is necessary due to the rising prevalence of ADHD, the chronic nature of ADHD symptoms and the limitations of the currently available medications. Full article

The mesolimbic reward system originating from dopamine neurons in the ventral tegmental area (VTA) of the midbrain shows a profound reduction in function during cannabinoid withdrawal. This condition may underlie aversive states that lead to compulsive drug seeking and relapse. The lateral habenula (LHb) exerts negative control over the VTA via the GABA rostromedial tegmental nucleus (RMTg), representing a potential convergence point for drug-induced opponent processes. We hypothesized that the LHb–RMTg pathway might be causally involved in the hypodopaminergic state during cannabinoid withdrawal. To induce Δ⁹-tetrahydrocannabinol (THC) dependence, adult male Sprague–Dawley rats were treated with THC (15 mg/kg, i.p.) twice daily for 6.5–7 days. Administration of the cannabinoid antagonist rimonabant (5 mg/kg, i.p.) precipitated a robust behavioral withdrawal syndrome, while abrupt THC suspension caused milder signs of abstinence. Extracellular single unit recordings confirmed a marked decrease in the discharge frequency and burst firing of VTA dopamine neurons during THC withdrawal. The duration of RMTg-evoked inhibition was longer in THC withdrawn rats. Additionally, the spontaneous activity of RMTg neurons and of LHb neurons was strongly depressed during cannabinoid withdrawal. These findings support the hypothesis that functional changes in the habenulo–mesencephalic circuit are implicated in the mechanisms underlying substance use disorders. Full article

Nicotine dependence is an important cause of excessive exposure to tobacco combustion compounds in most smokers. Nicotine replacement therapy is the main method to treat nicotine dependence, but it still has its shortcomings, such as the inability to mitigate withdrawal effects and limited applicability. It has been hypothesized that a combination of low-dose nicotine and caffeine could achieve the same psychological stimulation effect as a high dose of nicotine without causing nicotine withdrawal effects. To establish a model of nicotine dependence, male C57BL/6J mice were subcutaneously injected four times a day with nicotine (2 mg/kg) for 15 days and fed with water containing nicotine at the same time. They were randomly divided into four groups. After 24 h of withdrawal, different groups were injected with saline, nicotine (0.25 mg/kg or 0.1 mg/kg), or nicotine (0.1 mg/kg) and caffeine (20 mg/kg). Behavioral and physiological changes were evaluated by an assessment of physical signs, open field tests, elevated plus maze experiments, forced swimming tests, hot plate tests, and new-object-recognition tests. The changes in dopamine release in the prefrontal cortex (PFC) and ventral tegmental area (VTA) in the midbrain were analyzed using ELISA. The results showed that a combination of caffeine and nicotine could effectively relieve nicotine withdrawal syndrome, increase movement ability and pain thresholds, reduce anxiety and depression, enhance memory and cognitive ability, and increase the level of dopamine release in the PFC and VTA. Thus, caffeine combined with nicotine has potential as a stable and effective treatment option to help humans with smoking cessation. Full article

Dopaminergic neurons in the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNpc) comprise around 75% of all dopaminergic neurons in the human brain. While both groups of dopaminergic neurons are in close proximity in the midbrain and partially overlap, development, function, and impairments in these two classes of neurons are highly diverse. The molecular and cellular mechanisms underlying these differences are not yet fully understood, but research over the past decade has highlighted the need to differentiate between these two classes of dopaminergic neurons during their development and in the mature brain. This differentiation is crucial not only for understanding fundamental circuitry formation in the brain but also for developing therapies targeted to specific dopaminergic neuron classes without affecting others. In this review, we summarize the state of the art in our understanding of the differences between the dopaminergic neurons of the VTA and the SNpc, such as anatomy, structure, morphology, output and input, electrophysiology, development, and disorders, and discuss the current technologies and methods available for studying these two classes of dopaminergic neurons, highlighting their advantages, limitations, and the necessary improvements required to achieve more-precise therapeutic interventions. Full article

Major depressive disorder (MDD) is prevalent with a high subjective and socio-economic burden. Despite the effectiveness of classical treatment methods, 20–30% of patients stay treatment-resistant. Deep Brain Stimulation of the superolateral branch of the medial forebrain bundle is emerging as a clinical treatment. The stimulation region (ventral tegmental area, VTA), supported by experimental data, points to the role of dopaminergic (DA) transmission in disease pathology. This work sets out to develop a workflow that will allow the performance of analyses on midbrain DA-ergic neurons and projections in subjects who have committed suicide. Human midbrains were retrieved during autopsy, formalin-fixed, and scanned in a Bruker MRI scanner (7T). Sections were sliced, stained for tyrosine hydroxylase (TH), digitized, and integrated into the Montreal Neurological Institute (MNI) brain space together with a high-resolution fiber tract atlas. Subnuclei of the VTA region were identified. TH-positive neurons and fibers were semi-quantitatively evaluated. The study established a rigorous protocol allowing for parallel histological assessments and fiber tractographic analysis in a common space. Semi-quantitative readings are feasible and allow the detection of cell loss in VTA subnuclei. This work describes the intricate workflow and first results of an investigation of DA anatomy in VTA subnuclei in a growing naturalistic database. Full article

Exercise has increasingly been recognized as an adjunctive therapy for alcohol-use disorder (AUD), yet our understanding of its underlying neurological mechanisms remains limited. This knowledge gap impedes the development of evidence-based exercise guidelines for AUD treatment. Chronic ethanol (EtOH) exposure has been shown to upregulate and sensitize kappa opioid receptors (KORs) in the nucleus accumbens (NAc), which is innervated by dopamine (DA) neurons in the midbrain ventral tegmental area (VTA), which may contribute to AUD-related behaviors. In this study, we investigated the impact of voluntary exercise in EtOH-dependent mice on EtOH consumption, KOR and delta opioid receptor (DOR) expression in the NAc and VTA, and functional effects on EtOH-induced alterations in DA release in the NAc. Our findings reveal that voluntary exercise reduces EtOH consumption, reduces KOR and enhances DOR expression in the NAc, and modifies EtOH-induced adaptations in DA release, suggesting a competitive interaction between exercise-induced and EtOH-induced alterations in KOR expression. We also found changes to DOR expression in the NAc and VTA with voluntary exercise but no significant changes to DA release. These findings elucidate the complex interplay of AUD-related neurobiological processes, highlighting the potential for exercise as a therapeutic intervention for AUD. Full article