Deep brain stimulation of the orbitofrontal cortex prevents the development and reinstatement of morphine place preference

LF-DBS of the ventral striatum shortens persistence for morphine place preference and modulates BDNF expression in the hippocampus

BACKGROUND

Deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VC/VS) represents a promising therapy for treatment-refractory patients with substance-use disorders. We previously found that low-frequency (LF) DBS aimed to the VC/VS during extinction training strengthens the extinction memory for morphine seeking under a partial extinction protocol.

OBJECTIVES/HYPOTHESIS

In this study, animals were tested in a full extinction protocol to determine whether LF-DBS applied during extinction facilitates extinction while preventing drug reinstatement, and study the molecular mechanisms underlying the effects of LF-DBS, METHODS/RESULTS: We used a full extinction CPP paradigm combined with LF-DBS to assess behavior. Western blots for the pro-extinction molecule, brain-derived neurotrophic factor (BDNF) were then performed in corticomesolimbic regions of the brain. Lastly, to determine whether changes in BDNF expression elicited by LF-DBS were specific to the VS/NAc afferents from the hippocampus, amygdala, and medial prefrontal cortex, we performed BDNF-like immunohistochemistry, combined with the retrograde tracer cholera toxin B (CtB).

RESULTS

We showed a significant reduction in the number of days required to fully extinguish morphine CPP in animals exposed to LF-DBS during extinction training accompanied by a significant increase in BDNF expression in the hippocampus. However, LF-DBS applied during extinction did not prevent drug reinstatement. Lastly, no changes in BDNF/CtB double-labeled cells were found in VS/NAc projecting cells after one-day exposure to LF-DBS.

CONCLUSION(S)

These data suggest that LF-DBS can facilitate extinction of morphine CPP by decreasing drug seeking through potential synaptic plasticity changes in the hippocampus to strengthen extinction memories.

Memory Reconsolidation Updating in Substance Addiction: Applications, Mechanisms, and Future Prospects for Clinical Therapeutics

Persistent and maladaptive drug-related memories represent a key component in drug addiction. Converging evidence from both preclinical and clinical studies has demonstrated the potential efficacy of the memory reconsolidation updating procedure (MRUP), a non-pharmacological strategy intertwining two distinct memory processes: reconsolidation and extinction-alternatively termed "the memory retrieval-extinction procedure". This procedure presents a promising approach to attenuate, if not erase, entrenched drug memories and prevent relapse. The present review delineates the applications, molecular underpinnings, and operational boundaries of MRUP in the context of various forms of substance dependence. Furthermore, we critically examine the methodological limitations of MRUP, postulating potential refinement to optimize its therapeutic efficacy. In addition, we also look at the potential integration of MRUP and neurostimulation treatments in the domain of substance addiction. Overall, existing studies underscore the significant potential of MRUP, suggesting that interventions predicated on it could herald a promising avenue to enhance clinical outcomes in substance addiction therapy.

Non-invasive temporal interference brain stimulation reduces preference on morphine-induced conditioned place preference in rats

Long-term use of opioid drugs such as morphine can induce addiction in the central nervous system through dysregulation of the reward system of the brain. Deep brain stimulation (DBS) is a non-pharmacological technique capable of attenuating behavioral responses associated with opioid drug consumption and possesses the capability to selectively activate and target localized brain regions with a high spatial resolution. However, long-term implantation of electrodes in brain tissue may limit the effectiveness of DBS due to changes in impedance, position, and shape of the tip of the stimulation electrode and the risk of infection of nerve tissue around the implanted electrode. The main objective of the current study is to evaluate the effect of temporal interference (TI) brain stimulation on addictive behaviors of morphine-induced conditioned place preference (CPP) in rats. TI stimulation is a non-invasive technique used transcranially to modulate neural activity within targeted brain regions. It involves applying two high-frequency currents with slightly different frequencies, resulting in interference and targeted stimulation of different brain areas with the desired spatial resolution. The results indicated that TI stimulation with the amplitude ofI 1 = I 2 = 0.5 mA, carrier frequency of 2 kHz, frequency difference of 25 Hz, ON-OFF stimulation frequency of 0.25 Hz, and total duration of 10 min in three consecutive days resulted in a significant reduction of morphine preference in the morphine-stimulation group in comparison with the morphine group (p < 0.001). These findings highlight the potential of TI stimulation as a modulatory intervention in mitigating the addictive properties of morphine and provide valuable insights into the therapeutic implications of this stimulation paradigm for treatment of opioid drugs in human subjects.

Advances in Brain Stimulation, Nanomedicine and the Use of Magnetoelectric Nanoparticles: Dopaminergic Alterations and Their Role in Neurodegeneration and Drug Addiction

Recent advancements in brain stimulation and nanomedicine have ushered in a new era of therapeutic interventions for psychiatric and neurodegenerative disorders. This review explores the cutting-edge innovations in brain stimulation techniques, including their applications in alleviating symptoms of main neurodegenerative disorders and addiction. Deep Brain Stimulation (DBS) is an FDA-approved treatment for specific neurodegenerative disorders, including Parkinson's Disease (PD), and is currently under evaluation for other conditions, such as Alzheimer's Disease. This technique has facilitated significant advancements in understanding brain electrical circuitry by enabling targeted brain stimulation and providing insights into neural network function and dysfunction. In reviewing DBS studies, this review places particular emphasis on the underlying main neurotransmitter modifications and their specific brain area location, particularly focusing on the dopaminergic system, which plays a critical role in these conditions. Furthermore, this review delves into the groundbreaking developments in nanomedicine, highlighting how nanotechnology can be utilized to target aberrant signaling in neurodegenerative diseases, with a specific focus on the dopaminergic system. The discussion extends to emerging technologies such as magnetoelectric nanoparticles (MENPs), which represent a novel intersection between nanoformulation and brain stimulation approaches. These innovative technologies offer promising avenues for enhancing the precision and effectiveness of treatments by enabling the non-invasive, targeted delivery of therapeutic agents as well as on-site, on-demand stimulation. By integrating insights from recent research and technological advances, this review aims to provide a comprehensive understanding of how brain stimulation and nanomedicine can be synergistically applied to address complex neuropsychiatric and neurodegenerative disorders, paving the way for future therapeutic strategies.

Systematic review of rodent studies of deep brain stimulation for the treatment of neurological, developmental and neuropsychiatric disorders

Deep brain stimulation (DBS) modulates local and widespread connectivity in dysfunctional networks. Positive results are observed in several patient populations; however, the precise mechanisms underlying treatment remain unknown. Translational DBS studies aim to answer these questions and provide knowledge for advancing the field. Here, we systematically review the literature on DBS studies involving models of neurological, developmental and neuropsychiatric disorders to provide a synthesis of the current scientific landscape surrounding this topic. A systematic analysis of the literature was performed following PRISMA guidelines. 407 original articles were included. Data extraction focused on study characteristics, including stimulation protocol, behavioural outcomes, and mechanisms of action. The number of articles published increased over the years, including 16 rat models and 13 mouse models of transgenic or healthy animals exposed to external factors to induce symptoms. Most studies targeted telencephalic structures with varying stimulation settings. Positive behavioural outcomes were reported in 85.8% of the included studies. In models of psychiatric and neurodevelopmental disorders, DBS-induced effects were associated with changes in monoamines and neuronal activity along the mesocorticolimbic circuit. For movement disorders, DBS improves symptoms via modulation of the striatal dopaminergic system. In dementia and epilepsy models, changes to cellular and molecular aspects of the hippocampus were shown to underlie symptom improvement. Despite limitations in translating findings from preclinical to clinical settings, rodent studies have contributed substantially to our current knowledge of the pathophysiology of disease and DBS mechanisms. Direct inhibition/excitation of neural activity, whereby DBS modulates pathological oscillatory activity within brain networks, is among the major theories of its mechanism. However, there remain fundamental questions on mechanisms, optimal targets and parameters that need to be better understood to improve this therapy and provide more individualized treatment according to the patient's predominant symptoms.

Role of deep brain stimulation (DBS) in addiction disorders

Background

Addiction disorders pose significant challenges to public health, necessitating innovative treatments. This assesses deep brain stimulation (DBS) as a potential intervention for addiction disorders.

Methods

A literature review was carried out with a focus on the role of DBS in addiction disorders and its future implications in neurosurgical research.

Results

The online literature shows that DBS precisely modulates certain brain regions to restore addiction-related neural circuits and promote behavioral control.

Conclusion

Preclinical evidence demonstrates DBS's potential to rebalance neural circuits associated with addiction, and early clinical trials provide encouraging outcomes in enhancing addiction-related outcomes. Ethical considerations, long-term safety, and personalized patient selection require further investigation.

The reinstatement of the expression phase of morphine-induced conditioned place preference in male Wistar rats under ventral tegmental area stimulation and brief inactivation

Background and purpose

Previous research has found that the electrical stimulation of the ventral tegmental area (VTA) is involved in drug-dependent behaviors and plays a role in reward-seeking. However, the mechanisms remain unknown, especially the effect of electrical stimulation on this area. Therefore, this study aimed to investigate how the electrical stimulation and the temporary inactivation of VTA affect the morphine- dependent behavior in male rats.

Experimental approach

The adult Wistar male rats were anesthetized with ketamine and xylazine. The stimulation electrode (unilaterally) and the microinjection cannula (bilaterally) were implanted into the VTA, stereotaxically. Then, the rats underwent three-day of repeated conditioning with subcutaneous morphine (0.5 or 5 mg/kg) injections, in the conditioned place preference apparatus, followed by four-day forced abstinence, which altered their conditioning response to a morphine (0.5 mg/kg) priming dose on the ninth day. On that day, rats were given high- or low-intensity electrical stimulation or reversible inactivation with lidocaine (0.5 pL/site) in the VTA.

Findings/Results

Results showed that the electrical stimulation of the VTA with the high intensity (150 μA/rat), had a minimal effect on the expression of morphine-induced place conditioning in rats treated with a high dose (5 mg/kg) of morphine. However, the reversible inactivation of the VTA with lidocaine greatly increased place preference in rats treated with a low dose (0.5 mg/kg) of morphine. Additionally, the reinstatement of 0.5 mg/kg morphine-treated rats was observed after lidocaine infusion into the VTA.

Conclusion and implications

These results suggest that VTA electrical stimulation suppresses neuronal activation, but the priming dose causes reinstatement. The VTA may be a potential target for deep brain stimulation-based treatment of intractable disorders induced by substance abuse.

The electrical stimulation of the central nucleus of the amygdala in combination with dopamine receptor antagonist reduces the acquisition phase of morphine-induced conditioned place preference in male rat

Background and purpose

The central nucleus of the amygdala (CeA) is one of the nuclei involved in the reward system. The aim of the current study was to investigate the electrical stimulation (e-stim) effect of the CeA in combination with dopamine D1 receptor antagonist on morphine-induced conditioned place preference (CPP) in male rats.

Experimental approach

A 5-day procedure of CPP was used in this study. Morphine was administered at an effective dose of 5 mg/kg, and SCH23390 as a selective D1 receptor antagonist was administrated into the CeA. In addition, the CeA was stimulated with an intensity of the current of 150 μA. Finally, the dependence on morphine was evaluated in all experimental groups.

Findings/Results

Morphine significantly increased CPP. While the blockade of the D1 receptor of the CeA reduced the acquisition phase of morphine-induced CPP. Moreover, the combination of D1 receptor antagonist and e-stim suppressed morphine-induced CPP, even it induced an aversion.

Conclusion and implication

The current study suggests that the administration of dopamine D1 receptor antagonist into the CeA in combination with e-stim could play a prominent role in morphine dependence.

Restoring the firing activity of ventral tegmental area neurons by lateral hypothalamic deep brain stimulation following morphine administration in rats: LH DBS and the spiking activity of VTA neurons

We have previously shown that high-frequency deep brain stimulation (DBS) of the lateral hypothalamus (LH) compromises morphine-induced addiction-like behavior in rats. The exact mechanism underlying this effect is not known. Here, we investigated the assumption that DBS in the LH influences the firing activity of neurons in the ventral tegmental area (VTA). To that end, male Wistar rats received morphine (5 mg/kg; s.c.) for three days and underwent extracellular single unit recording under general anesthesia one day later. During the recording, the rats received an intraoperative injection of morphine (5 mg/kg; s.c.) plus DBS in the LH (130 Hz pulse frequency, 150 μA amplitude, and 100 μs pulse width). One group of animals also received preoperative DBS after each morphine injection before the recording. The spiking frequency of VTA neurons was measured at three successive phases: (1) baseline (5-15 min); (2) DBS-on (morphine + DBS for 30 min); and (3) After-DBS (over 30 min after termination of DBS). Results showed that morphine suppressed the firing activity of a large population of non-DA neurons, whereas it activated most DA neurons. Intraoperative DBS reversed morphine suppression of non-DA firing, but did not alter the excitatory effect of morphine on DA neurons firing. With repeated preoperative application of DBS, non-DA neurons returned to the morphine-induced suppressive state, but DA neurons released from the excitatory effect of morphine. It is concluded that the development of morphine reward is associated with a hypoactivity of VTA non-DA neurons and a hyperactivity of DA neurons, and that DBS modulation of the spiking activity may contribute to the blockade of morphine addiction-like behavior.

A wide range of Deep Brain Stimulation of the nucleus accumbens shell time independently reduces the extinction period and prevents the reinstatement of methamphetamine-seeking behavior in rats

Methamphetamine (METH) addiction is a significant public health issue, and standard medical therapies are often not curative. Deep Brain Stimulation (DBS) has recently shown the potential to cure addiction by modulating neural activity in specific brain circuits. Recent studies have revealed that the nucleus accumbens shell (NAcSh) could serve as a promising target in treating addiction. Therefore, the present study aimed to investigate the therapeutic effects of NAcSh high- or low-frequency stimulation (HFS or LFS) in the different time points of application on the extinction and reinstatement of the METH-conditioned place preference (CPP). LFS or HFS (10 or 130 Hz, 150-200 μA, 100 μs) was delivered to the NAcSh for 30 min non-simultaneous (in a distinct non-drug environment) or simultaneous (in a drug-paired context) of the drug-free extinction sessions. The obtained results showed that both non-simultaneous and simultaneous treatments by HFS and LFS notably reduced the extinction period of METH-induced CPP. Furthermore, the data indicated that both non-synchronous and synchronous HFS prevented METH-primed reinstatement, while only the LFS synchronized group could block the reinstatement of METH-seeking behavior. The results also demonstrated that HFS was more effective than LFS in attenuating METH-primed reinstatement, and applying HFS synchronous was significantly more effective than HFS non-synchronous in reducing the relapse of drug-seeking. In conclusion, the current study's results suggest that DBS of the NAcSh in a wide range of frequencies (LFS and HFS) could affect addiction-related behaviors. However, it should be considered that the frequency and timing of DBS administration are among the critical determining factors.

Distinct suppressing effects of deep brain stimulation in the orbitofrontal cortex on the development, extinction, and reinstatement of methamphetamine-seeking behaviors

AIMS

The orbitofrontal cortex (OFC) is implicated in compulsive drug-seeking and relapse, the characteristics that result in addiction treatment failure. Structural and functional impairments within the OFC have been detected in many substance use disorders (SUDs). Deep brain stimulation (DBS) is proposed as a promising therapeutic option in treating SUDs. Therefore, the present study aimed to investigate the potential efficacy of DBS application on the various stages of the methamphetamine-conditioned place preference (CPP) paradigm in rats.

MAIN METHODS

Electrodes were implanted unilaterally in the rat's right OFC. DBS in the form of high- or low-frequency stimulation (HFS: 130 Hz, LFS: 13 Hz) was applied during the 5-day conditioning phase (a daily 30-min session) or extinction period (30-min session, daily, ten days) of methamphetamine-induced CPP in two separate sets of experiments. Following extinction, place preference was reinstated by injecting a priming dose of methamphetamine (0.25 mg/kg).

KEY FINDINGS

The HFS and LFS significantly decreased the methamphetamine place preference when applied over the conditioning period. In the extinction experiment, only HFS could remarkably accelerate the extinction of reward-context associations and even reduce the methamphetamine-induced reinstatement of seeking behaviors.

SIGNIFICANCE

Conclusively, DBS administration in the OFC demonstrated some positive results, including suppressing effects on the development, maintenance, and relapse of methamphetamine-seeking behavior. These findings encourage conducting more preclinical studies to strongly suggest a wide range of DBS applications in cortical areas such as OFC as an efficient treatment modality for psychostimulant use disorder.

Deep brain stimulation of the lateral hypothalamus to block morphine reward: Does the intensity of stimulation matter?

It has been shown that high-frequency deep brain stimulation (DBS) of the lateral hypothalamus (LH) prevents morphine-induced conditioned place preference (CPP) in rats. However, our previous study demonstrated that the application of DBS at 150 µA did not block morphine CPP in all rats. Here, we investigated the possibility to completely block morphine CPP by increasing the intensity of LH DBS. Morphine reward was assessed by the CPP paradigm in male Wistar rats. DBS was applied in the LH during the conditioning trials with morphine (5 mg/kg, S.C.) at 130 Hz pulse frequency, 100 µs pulse duration, and either 150 µA or 200 µA pulse amplitude. Results showed that repeated morphine injections produced a robust CPP that was blocked partially by DBS at 150 µA and completely by DBS at 200 µA. Response rate was 47% with 150-µA and 100% with 200-µA stimulation. DBS treatment was not associated with changes in motor activity. In conclusion, the development of morphine reward was modulated by LH DBS in an intensity-dependent manner.

Partial recovery of the left DLPFC-right insula circuit with reduced craving in abstinent heroin users: a longitudinal study

The phenomenon of brain recovery after long-term abstinence has been reported in substance use disorders. However, few longitudinal studies have been conducted to observe the potential recovery in heroin users, and little is known about the neural mechanism underlying the decreased craving after prolonged abstinence. The 8-month longitudinal study was carried out in 29 heroin users and 30 healthy controls. By choosing the L_DLPFC, which was activated by the heroin cue as the seeding region, different brain connection patterns were compared between healthy controls and heroin users by using Granger causality analysis (GCA) at baseline. Then, a paired t test was employed to detect the potential recovery of L_DLPFC circuits after prolonged abstinence. The visual analog scale (VAS) and trail-making test-A (TMT-A) were adopted to investigate craving and cognitive control impairment, respectively. The neuroimaging changes were then correlated with behavioral improvements. Similar analyses were applied for the mirrored right DLPFC to verify the lateralization hypothesis of the DLPFC in addiction. In the longitudinal study, enhanced GCA coefficients were observed in the L_DLPFC-R_insula circuit of heroin users after long-term abstinence and were associated with craving score changes. At baseline, decreased GCA coefficients from the left DLPFC to the bilateral SMA and right putamen, together with the reduced GCA strength from the bilateral OFC to the left DLPFC, were found between HUs and HCs. Our findings extended the brain recovery phenomenon into the field of heroin and suggested that the increased regulation of the L_DLPFC over the insula after prolonged abstinence was important for craving inhibition.

Potential brain recovery of frontostriatal circuits in heroin users after prolonged abstinence: A preliminary study

Neuroscientists have devoted efforts to explore potential brain recovery after prolonged abstinence in heroin users (HU). However, not much is known about whether frontostriatal circuits can recover after prolonged abstinence in HU. An eight-month longitudinal study was carried out for HU. Two MRI scans were obtained at baseline (HU1) and 8-month follow-up (HU2). The functional and structural connectivities of dorsal and ventral frontostriatal pathways were measured by resting-state functional connectivity (RSFC) and diffusion tensor imaging (DTI). Correlation analyses were employed to reveal the associations between neuroimaging and behavioral changes. Results suggested that relative to healthy controls (HCs), HU1 showed lower fractional anisotropy (FA) in the right dorsolateral prefrontal cortex (DLPFC)-to-caudate tracts and medial orbitofrontal cortex (mOFC)-to-nucleus accumbens (NAc) tracts as well as decreased RSFC in the left mOFC-NAc circuits. Longitudinal results revealed reduced craving and enhanced cognitive control in HU2 compared with HU1. After prolonged abstinence, HU2 showed increased FA values in the right DLPFC-caudate and mOFC-NAc tracts as well as increased RSFC strength in the bilateral mOFC-NAc circuits compared with HU1. In addition, changes in RSFC and FA values in the right mOFC-NAc circuit were negatively correlated with craving score changes. Similarly, negative correlations were also found between changes of RSFC in the bilateral DLPFC-caudate circuits and TMT-A scores. We provided scientific evidence for brain recovery of the dorsal and ventral frontostriatal circuits in HU after prolonged abstinence, and these circuits may be potential neuroimaging biomarkers for cognition and craving changes.

Deep Brain Stimulation for Addictive Disorders-Where Are We Now?

In the face of a global epidemic of drug addiction, neglecting to develop new effective therapies will perpetuate the staggering human and economic costs of substance use. This review aims to summarize and evaluate the preclinical and clinical studies of deep brain stimulation (DBS) as a novel therapy for refractory addiction, in hopes to engage and inform future research in this promising novel treatment avenue. An electronic database search (MEDLINE, EMBASE, Cochrane library) was performed using keywords and predefined inclusion criteria between 1974 and 6/18/2021 (registered on Open Science Registry). Selected articles were reviewed in full text and key details were summarized and analyzed to understand DBS' therapeutic potential and possible mechanisms of action. The search yielded 25 animal and 22 human studies. Animal studies showed that DBS of targets such as nucleus accumbens (NAc), insula, and subthalamic nucleus reduces drug use and seeking. All human studies were case series/reports (level 4/5 evidence), mostly targeting the NAc with generally positive outcomes. From the limited evidence in the literature, DBS, particularly of the NAc, appears to be a reasonable last resort option for refractory addictive disorders. We propose that future research in objective electrophysiological (e.g., local field potentials) and neurochemical (e.g., extracellular dopamine levels) biomarkers would assist monitoring the progress of treatment and developing a closed-loop DBS system. Preclinical literature also highlighted the prefrontal cortex as a promising DBS target, which should be explored in human research.

Deep brain stimulation for opioid use disorder: A systematic review of preclinical and clinical evidence

Opioid use disorder (OUD) is a chronic and complex disease characterized by repeated relapses and remissions. Deep brain stimulation (DBS) has been discussed again and again as a potentially helpful neuromodulatory procedure in this context. In this review, for the first time, we intended to systematically identify the positive and negative effects of DBS in human and animal models of opioid dependence to assess the viability of DBS as a treatment of OUD. Eligible studies were incorporated by a comprehensive literature search and evaluated through proper methodological quality assessment tools. Findings showed that the nucleus accumbens was the most stimulated brain target in human and animal studies, and DBS was applied chiefly in the form of high-frequency stimulation (HFS). DBS administration effectively reduced opioid craving and consumption in human and animal subjects dependent on opioids. DBS represents a valuable alternative strategy for treating intractable opioid addiction. Based on our systematic literature analysis, research efforts in this field should be continued.

The interaction between sexual reward/ deprivation and the acquisition, extinction and reinstatement of morphine-seeking behavior

Natural rewards and abused drugs affect the function of the common brain's reward system. Interaction between social and drug rewards can change the vulnerability to development of drug addiction. Here, we investigate the effects of sexual experience and sex deprivation on the acquisition, maintenance, and drug prime-induced reinstatement of morphine-seeking behavior in male mice using conditioned place preference (CPP). CPP induced with morphine (3, 5, 7 mg/kg, s.c. for 3 days) lasted for 10 days after cessation of morphine treatment and priming dose of morphine (2 mg/kg, s.c.) reinstated the extinguished CPP. In the post-test phase, sexually experienced animals showed a lower preference for morphine compared to sex-deprived males. In the extinction phase, sex deprivation shortened maintenance time compared to control animals. The preference for morphine in sexually experienced animals did not diminish by the seventeenth extinction day. In both groups, the priming injection of morphine after the extinction period could reinstate the extinguished morphine-induced CPP. Together, these data showed the interaction between sex and drug reward and that sexual behavior -a natural rewarding stimulus- can prolong, whereas sex deprivation can block the maintenance of morphine-seeking behaviors. Sexual experience may induce functional and morphological alterations in brain reward areas particularly the mesolimbic system similar to repeated exposure to abused drugs which can affect morphine-seeking behaviors.

Deep Brain Stimulation in Drug Addiction Treatment: Research Progress and Perspective

Drug addiction is a chronic psychiatric disorder characterized by compulsive drug-seeking and drug-using behavior, and a tremendous socioeconomic burden to society. Current pharmacological and psychosocial methods have shown limited treatment effects for substance abuse. Deep Brain Stimulation (DBS) is a novel treatment for psychiatric disease and has gradually gained popularity in the treatment of addiction. Addiction is characterized by neuroplastic changes in the nucleus accumbens (NAc), a key structure in the brain reward system, and DBS in this region has shown promising treatment effects. In this paper, the research progress on DBS for drug addiction has been reviewed. Specifically, we discuss the mechanism of NAc DBS for addiction treatment and summarize the results of clinical trials on DBS treatment for addiction to psychoactive substances such as nicotine, alcohol, cocaine, opioids and methamphetamine/amphetamine. In addition, the treatment effects of DBS in other brain regions, such as the substantia nigra pars reticulata (SNr) and insula are discussed.

High-Frequency Deep Brain Stimulation of the Substantia Nigra Pars Reticulata Facilitates Extinction and Prevents Reinstatement of Methamphetamine-Induced Conditioned Place Preference

Persistent and stable drug memories lead to a high rate of relapse among addicts. A number of studies have found that intervention in addiction-related memories can effectively prevent relapse. Deep brain stimulation (DBS) exhibits distinct therapeutic effects and advantages in the treatment of neurological and psychiatric disorders. In addition, recent studies have also found that the substantia nigra pars reticulata (SNr) could serve as a promising target in the treatment of addiction. Therefore, the present study aimed to investigate the effect of DBS of the SNr on the reinstatement of drug-seeking behaviors. Electrodes were bilaterally implanted into the SNr of rats before training of methamphetamine-induced conditioned place preference (CPP). High-frequency (HF) or low-frequency (LF) DBS was then applied to the SNr during the drug-free extinction sessions. We found that HF DBS, during the extinction sessions, facilitated extinction of methamphetamine-induced CPP and prevented drug-primed reinstatement, while LF DBS impaired the extinction. Both HF and LF DBS did not affect locomotor activity or induce anxiety-like behaviors of rats. Finally, HF DBS had no effect on the formation of methamphetamine-induced CPP. In conclusion, our results suggest that HF DBS of the SNr could promote extinction and prevent reinstatement of methamphetamine-induced CPP, and the SNr may serve as a potential therapeutic target in the treatment of drug addiction.

Consolidating the Circuit Model for Addiction

Addiction is a disease characterized by compulsive drug seeking and consumption observed in 20-30% of users. An addicted individual will favor drug reward over natural rewards, despite major negative consequences. Mechanistic research on rodents modeling core components of the disease has identified altered synaptic transmission as the functional substrate of pathological behavior. While the initial version of a circuit model for addiction focused on early drug adaptive behaviors observed in all individuals, it fell short of accounting for the stochastic nature of the transition to compulsion. The model builds on the initial pharmacological effect common to all addictive drugs-an increase in dopamine levels in the mesolimbic system. Here, we consolidate this early model by integrating circuits underlying compulsion and negative reinforcement. We discuss the genetic and epigenetic correlates of individual vulnerability. Many recent data converge on a gain-of-function explanation for circuit remodeling, revealing blueprints for novel addiction therapies.

Deep Brain Stimulation of the Lateral Hypothalamus Facilitates Extinction and Prevents Reinstatement of Morphine Place Preference in Rats

OBJECTIVES

We have previously shown that high-frequency (HF) deep brain stimulation (DBS) of the lateral hypothalamus (LH) during the acquisition phase of morphine-induced conditioned place preference (CPP) abolished the development of morphine reward. In the present study, we investigated the effect of DBS in the LH during the extinction phase of morphine CPP.

MATERIALS AND METHODS

Rats were implanted with electrodes in the LH and went through conditioning trials for morphine CPP (40 min each, for three days), followed by extinction trials (20 min, for nine days). DBS-like stimulation (square pulses at 13 or 130 Hz, 200 μA, 100 μsec) was applied during the extinction trials.

RESULTS

Rats that received HF-DBS (130 Hz) accomplished extinction of morphine place preference by day 5 of the phase, whereas those in sham-stimulation or low-frequency-DBS (LF-DBS, 13 Hz) groups reached the criterion for extinction at day 8. One day later, rats received a priming injection of morphine (2 mg/kg) to reinstate the extinguished preference. While rats in the sham-DBS and LF-DBS relapsed into the state of preferring morphine-associated context, those in the HF-DBS group did not show such preference. Rats were then proceeded into an additional phase of extinction training (20 min, once daily, three to five days) with DBS, followed by restraint stress-induced reinstatement test. Again, sham-DBS and LF-DBS had no effect on relapse to the morphine place preferring state, but HF-DBS completely prevented the relapse.

CONCLUSION

HF-DBS facilitated extinction of morphine place preference and disrupted drug priming- and stress-induced renewal of morphine place preference.

Continuous High Frequency Deep Brain Stimulation of the Rat Anterior Insula Attenuates the Relapse Post Withdrawal and Strengthens the Extinction of Morphine Seeking

Deep brain stimulation (DBS) modulates the neuronal activity in specific brain circuits and has been recently considered as a promising intervention for refractory addiction. The insula cortex is the hub of interoception and is known to be involved in different aspects of substance use disorder. In the present study, we investigate the effects of continuous high frequency DBS in the anterior insula (AI) on drug-seeking behaviors and examined the molecular mechanisms of DBS action in morphine-addicted rats. Sprague-Dawley rats were trained to the morphine-conditioned place preference (CPP, day 1-8) followed by bilaterally implanted with DBS electrodes in the AI (Day 10) and recovery (Day 10-15). Continuous high-frequency (HF) -DBS (130 Hz, 150 μA, 90 μs) was applied during withdrawal (Day 16-30) or extinction sessions. CPP tests were conducted on days 16, 30, 40 during withdrawal session and several rats were used for proteomic analysis on day 30. Following the complete extinction, morphine-CPP was reinstated by a priming dose of morphine infusion (2 mg/kg). The open field and novel objective recognition tests were also performed to evaluate the DBS side effect on the locomotion and recognition memory. Continuous HF-DBS in the AI attenuated the expression of morphine-CPP post-withdrawal (Day 30), but morphine addictive behavior relapsed 10 days after the cessation of DBS (Day 40). Continuous HF-DBS reduced the period to full extinction of morphine-CPP and blocked morphine priming-induced recurrence of morphine addiction. HF-DBS in the AI had no obvious effect on the locomotor activity and novel objective recognition and did not cause anxiety-like behavior. In addition, our proteomic analysis identified eight morphine-regulated proteins in the AI and their expression levels were reversely changed by HF-DBS. Continuous HF-DBS in the bilateral anterior insula prevents the relapse of morphine place preference after withdrawal, facilitates its extinction, blocks the reinstatement induced by morphine priming and reverses the expression of morphine-regulated proteins. Our findings suggest that manipulation of insular activity by DBS could be a potential intervention to treat substance use disorder, although future research is warranted.