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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.
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Objectives: Opioid use disorder (OUD)-associated overdose deaths have reached epidemic proportions worldwide. An important driving force for relapse is anxiety associated with opioid withdrawal. We hypothesized that our new technology, termed heterodyned whole-body vibration (HWBV) would ameliorate anxiety associated with OUD. Methods: Using a randomized, placebo (sham)-controlled, double-blind study design in an NIH-sponsored Phase 1 trial, we evaluated 60 male and 26 female participants diagnosed with OUD and undergoing treatment at pain and rehabilitation clinics. We utilized the Hamilton Anxiety Scale (HAM-A) and a daily visual analog scale anxiety rating (1-10) to evaluate anxiety. Subjects were treated for 10 min 5X/week for 4 weeks with either sham vibration (no interferential beat or harmonics) or HWBV (beats and harmonics). The participants also completed a neuropsychological test battery at intake and discharge. Results: In OUD subjects with moderate anxiety, there was a significant improvement in daily anxiety scores in the HWBV group compared to the sham treatment group (p=3.41 × 10-7). HAM-A scores in OUD participants at intake showed moderate levels of anxiety in OUD participants (HWBV group: 15.9 ± 1.6; Sham group: 17.8 ± 1.6) and progressively improved in both groups at discharge, but improvement was greater in the HWBV group (p=1.37 × 10-3). Furthermore, three indices of neuropsychological testing (mental rotations, spatial planning, and response inhibition) were significantly improved by HWBV treatment. Conclusions: These findings support HWBV as a novel, non-invasive, non-pharmacological treatment for anxiety associated with OUD.
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Iboga alkaloids, also known as coronaridine congeners, have shown promise in the treatment of alcohol and opioid use disorders. The objective of this study was to evaluate the effects of catharanthine and 18-methoxycoronaridine (18-MC) on dopamine (DA) transmission and cholinergic interneurons in the mesolimbic DA system, nicotine-induced locomotor activity, and nicotine-taking behavior. Utilizing ex vivo fast-scan cyclic voltammetry (FSCV) in the nucleus accumbens core of male mice, we found that catharanthine or 18-MC differentially inhibited evoked DA release. Catharanthine inhibition of evoked DA release was significantly reduced by both α4 and α6 nicotinic acetylcholine receptors (nAChRs) antagonists. Additionally, catharanthine substantially increased DA release more than vehicle during high-frequency stimulation, although less potently than an α4 nAChR antagonist, which confirms previous work with nAChR antagonists. Interestingly, while catharanthine slowed DA reuptake measured via FSCV ex vivo, it also increased extracellular DA in striatal dialysate from anesthetized mice in vivo in a dose-dependent manner. Superfusion of catharanthine or 18-MC inhibited the firing rate of striatal cholinergic interneurons in a concentration dependent manner, which are known to potently modulate presynaptic DA release. Catharanthine or 18-MC suppressed acetylcholine currents in oocytes expressing recombinant rat α6/α3ß2ß3 or α6/α3ß4 nAChRs. In behavioral experiments using male Sprague-Dawley rats, systemic administration of catharanthine or 18-MC blocked nicotine enhancement of locomotor activity. Importantly, catharanthine attenuated nicotine self-administration in a dose-dependent manner while having no effect on food reinforcement. Lastly, administration of catharanthine and nicotine together greatly increased head twitch responses, indicating a potential synergistic hallucinogenic effect. These findings demonstrate that catharanthine and 18-MC have similar, but not identical effects on striatal DA dynamics, striatal cholinergic interneuron activity and nicotine psychomotor effects.
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Proteínas de Transporte de Dopamina a través de la Membrana Plasmática , Dopamina , Ibogaína , Ibogaína/análogos & derivados , Nicotina , Receptores Nicotínicos , Animales , Dopamina/metabolismo , Masculino , Receptores Nicotínicos/metabolismo , Receptores Nicotínicos/efectos de los fármacos , Nicotina/farmacología , Ibogaína/farmacología , Ratones , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Ratones Endogámicos C57BL , Antagonistas Nicotínicos/farmacología , Oocitos/efectos de los fármacos , Agonistas Nicotínicos/farmacología , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Autoadministración , Xenopus laevis , Interneuronas/efectos de los fármacos , Interneuronas/metabolismo , Relación Dosis-Respuesta a Droga , Actividad Motora/efectos de los fármacosRESUMEN
Ivermectin (IVM) is a commonly prescribed antiparasitic treatment with pharmacological effects on invertebrate glutamate ion channels resulting in paralysis and death of invertebrates. However, it can also act as a modulator of some vertebrate ion channels and has shown promise in facilitating L-DOPA treatment in preclinical models of Parkinson's disease. The pharmacological effects of IVM on dopamine terminal function were tested, focusing on the role of two of IVM's potential targets: purinergic P2X4 and nicotinic acetylcholine receptors. Ivermectin enhanced electrochemical detection of dorsal striatum dopamine release. Although striatal P2X4 receptors were observed, IVM effects on dopamine release were not blocked by P2X4 receptor inactivation. In contrast, IVM attenuated nicotine effects on dopamine release, and antagonizing nicotinic receptors prevented IVM effects on dopamine release. IVM also enhanced striatal cholinergic interneuron firing. L-DOPA enhances dopamine release by increasing vesicular content. L-DOPA and IVM co-application further enhanced release but resulted in a reduction in the ratio between high and low frequency stimulations, suggesting that IVM is enhancing release largely through changes in terminal excitability and not vesicular content. Thus, IVM is increasing striatal dopamine release through enhanced cholinergic activity on dopamine terminals.
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Peripheral mechanoreceptor-based treatments such as acupuncture and chiropractic manipulation have shown success in modulating the mesolimbic dopamine (DA) system originating in the ventral tegmental area (VTA) of the midbrain and projecting to the nucleus accumbens (NAc) of the striatum. We have previously shown that mechanoreceptor activation via whole-body vibration (WBV) ameliorates neuronal and behavioral effects of chronic ethanol exposure. In this study, we employ a similar paradigm to assess the efficacy of WBV as a preventative measure of neuronal and behavioral effects of morphine withdrawal in a Wistar rat model. We demonstrate that concurrent administration of WBV at 80 Hz with morphine over a 5-day period significantly reduced adaptations in VTA GABA neuronal activity and NAc DA release and modulated expression of δ-opioid receptors (DORs) on NAc cholinergic interneurons (CINs) during withdrawal. We also observed a reduction in behavior typically associated with opioid withdrawal. WBV represents a promising adjunct to current intervention for opioid use disorder (OUD) and should be examined translationally in humans.
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Terapia por Acupuntura , Morfina , Humanos , Ratas , Animales , Ratas Wistar , Vibración/uso terapéutico , InterneuronasRESUMEN
Dopamine transmission from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) regulates important aspects of motivation and is influenced by the neuroimmune system. The neuroimmune system is a complex network of leukocytes, microglia and astrocytes that detect and remove foreign threats like bacteria or viruses and communicate with each other to regulate non-immune (e.g neuronal) cell activity through cytokine signaling. Inflammation is a key regulator of motivational states, though the effects of specific cytokines on VTA circuitry and motivation are largely unknown. Therefore, electrophysiology, neurochemical, immunohistochemical and behavioral studies were performed to determine the effects of the anti-inflammatory cytokine interleukin-10 (IL-10) on mesolimbic activity, dopamine transmission and conditioned behavior. IL-10 enhanced VTA dopamine firing and NAc dopamine levels via decreased VTA GABA currents in dopamine neurons. The IL-10 receptor was localized on VTA dopamine and non-dopamine cells. The IL-10 effects on dopamine neurons required post-synaptic phosphoinositide 3-kinase activity, and IL-10 appeared to have little-to-no efficacy on presynaptic GABA terminals. Intracranial IL-10 enhanced NAc dopamine levels in vivo and produced conditioned place aversion. Together, these studies identify the IL-10R on VTA dopamine neurons as a potential regulator of motivational states.
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Dopamina , Área Tegmental Ventral , Dopamina/farmacología , Neuronas Dopaminérgicas/fisiología , Interleucina-10/farmacología , Fosfatidilinositol 3-Quinasas , Núcleo Accumbens , Ácido gamma-Aminobutírico/farmacologíaRESUMEN
The prevailing view is that enhancement of dopamine (DA) transmission in the mesolimbic system, consisting of DA neurons in the ventral tegmental area (VTA) that project to the nucleus accumbens (NAc), underlies the reward properties of ethanol (EtOH) and nicotine (NIC). We have shown previously that EtOH and NIC modulation of DA release in the NAc is mediated by α6-containing nicotinic acetylcholine receptors (α6*-nAChRs), that α6*-nAChRs mediate low-dose EtOH effects on VTA GABA neurons and EtOH preference, and that α6*-nAChRs may be a molecular target for low-dose EtOH. However, the most sensitive target for reward-relevant EtOH modulation of mesolimbic DA transmission and the involvement of α6*-nAChRs in the mesolimbic DA reward system remains to be elucidated. The aim of this study was to evaluate EtOH effects on GABAergic modulation of VTA GABA neurons and VTA GABAergic input to cholinergic interneurons (CINs) in the NAc. Low-dose EtOH enhanced GABAergic input to VTA GABA neurons that was blocked by knockdown of α6*-nAChRs. Knockdown was achieved either by α6-miRNA injected into the VTA of VGAT-Cre/GAD67-GFP mice or by superfusion of the α-conotoxin MII[H9A;L15A] (MII). Superfusion of MII blocked EtOH inhibition of mIPSCs in NAc CINs. Concomitantly, EtOH enhanced CIN firing rate, which was blocked by knockdown of α6*-nAChRs with α6-miRNA injected into the VTA of VGAT-Cre/GAD67-GFP mice. The firing rate of CINs was not enhanced by EtOH in EtOH-dependent mice, and low-frequency stimulation (LFS; 1 Hz, 240 pulses) caused inhibitory long-term depression at this synapse (VTA-NAc CIN-iLTD) which was blocked by knockdown of α6*-nAChR and MII. Ethanol inhibition of CIN-mediated evoked DA release in the NAc was blocked by MII. Taken together, these findings suggest that α6*-nAChRs in the VTA-NAc pathway are sensitive to low-dose EtOH and play a role in plasticity associated with chronic EtOH.
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MicroARNs , Receptores Nicotínicos , Ratones , Animales , Receptores Nicotínicos/metabolismo , Núcleo Accumbens/metabolismo , Nicotina/farmacología , Transmisión Sináptica , Área Tegmental Ventral/metabolismo , Etanol/farmacología , Colinérgicos/farmacología , Interneuronas/metabolismo , MicroARNs/metabolismoRESUMEN
Opioid use and withdrawal evokes behavioral adaptations such as drug seeking and anxiety, though the underlying neurocircuitry changes are unknown. The basolateral amygdala (BLA) regulates these behaviors through principal neuron activation. Excitatory BLA pyramidal neuron activity is controlled by feedforward inhibition provided, in part, by lateral paracapsular (LPC) GABAergic inhibitory neurons, residing along the BLA/external capsule border. LPC neurons express µ-opioid receptors (MORs) and are potential targets of opioids in the etiology of opioid-use disorders and anxiety-like behaviors. Here, we investigated the effects of opioid exposure on LPC neuron activity using immunohistochemical and electrophysiological approaches. We show that LPC neurons, and other nearby BLA GABA and non-GABA neurons, express MORs and δ-opioid receptors. Additionally, DAMGO, a selective MOR agonist, reduced GABA but not glutamate-mediated spontaneous postsynaptic currents in LPC neurons. Furthermore, in LPC neurons, abstinence from repeated morphine-exposure in vivo (10 mg/kg/day, 5 days, 2 days off) decrease the intrinsic membrane excitability, with a ~75% increase in afterhyperpolarization and ~40-50% enhanced adenylyl cyclase-dependent activity in LPC neurons. These data show that MORs in the BLA are a highly sensitive targets for opioid-induced inhibition and that repeated opioid exposure results in impaired LPC neuron excitability.
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Amígdala del Cerebelo , Analgésicos Opioides , Ratas , Animales , Analgésicos Opioides/farmacología , Ratas Sprague-Dawley , Neuronas GABAérgicas , Receptores OpioidesRESUMEN
Therapeutic activation of mechanoreceptors (MStim) in osteopathy, chiropractic and acupuncture has been in use for hundreds of years with a myriad of positive outcomes. It has been previously shown to modulate the firing rate of neurons in the ventral tegmental area (VTA) and dopamine (DA) release in the nucleus accumbens (NAc), an area of interest in alcohol-use disorder (AUD). In this study, we examined the effects of MStim on VTA GABA neuron firing rate, DA release in the NAc, and behavior during withdrawal from chronic EtOH exposure in a rat model. We demonstrate that concurrent administration of MStim and EtOH significantly reduced adaptations in VTA GABA neurons and DA release in response to a reinstatement dose of EtOH (2.5 g/kg). Behavioral indices of EtOH withdrawal (rearing, open-field crosses, tail stiffness, gait, and anxiety) were substantively ameliorated with concurrent application of MStim. Additionally, MStim significantly increased the overall frequency of ultrasonic vocalizations, suggesting an increased positive affective state.
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Dopamina , Área Tegmental Ventral , Ratas , Animales , Dopamina/farmacología , Neuronas GABAérgicas , Etanol/farmacología , Núcleo AccumbensRESUMEN
Dopamine (DA) is a cell-signaling molecule that does not readily cross the blood-brain barrier. Despite this, peripherally administered DA enhances DA levels in the nucleus accumbens and alters DA-related behaviors. This study was designed to investigate whether DA subtype-2 receptors are involved in the enhancement of nucleus accumbens (NAc) DA levels elicited by intravenous DA administration. This was accomplished by using microdialysis in the NAc and extracellular single unit recordings of putative DA neurons in the ventral tegmental area (VTA). Additionally, the reinforcing properties of intravenous DA were investigated using a place conditioning paradigm and the effects of intravenous DA on ultrasonic vocalizations were assessed. Following administration of intravenous dopamine, the firing rate of putative DA neurons in the VTA displayed a biphasic response and DA levels in the nucleus accumbens were enhanced. Pretreatment with domperidone, a peripheral-only DA D2 receptor (D2R) antagonist, reduced intravenous DA mediated increases in VTA DA neuron activity and NAc DA levels. Pretreatment with phentolamine, a peripheral α-adrenergic receptor antagonist, did not alter the effects of IV DA on mesolimbic DA neurotransmission. These results provide evidence for peripheral D2R mediation of the effects of intravenous DA on mesolimbic DA signaling.
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Dysregulation of biological rhythms plays a role in a wide range of psychiatric disorders. We report mechanistic insights into the rhythms of rapid dopamine signals and cholinergic interneurons (CINs) working in concert in the rodent striatum. These rhythms mediate diurnal variation in conditioned responses to reward-associated cues. We report that the dopamine signal-to-noise ratio varies according to the time of day and that phasic signals are magnified during the middle of the dark cycle in rats. We show that CINs provide the mechanism for diurnal variation in rapid dopamine signals by serving as a gain of function to the dopamine signal-to-noise ratio that adjusts across time of day. We also show that conditioned responses to reward-associated cues exhibit diurnal rhythms, with cue-directed behaviors observed exclusively midway through the dark cycle. We conclude that the rapid dopamine signaling rhythm is mediated by a diurnal rhythm in CIN activity, which influences learning and motivated behaviors across the time of day.
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Ritmo Circadiano , Dopamina , Animales , Colinérgicos , Condicionamiento Clásico , Humanos , Núcleo Accumbens/fisiología , Ratas , RecompensaRESUMEN
Fast-scan cyclic voltammetry (FSCV) is an effective tool for measuring dopamine release and clearance throughout the brain, especially the striatum where dopamine terminals are abundant and signals are heavily regulated by release machinery and the dopamine transporter (DAT). Peak height measurement is perhaps the most common method for measuring dopamine release, but it is influenced by changes in clearance. Michaelis-Menten-based modeling has been a standard in measuring dopamine clearance, but it is problematic in that it requires experimenter fitted modeling subject to experimenter bias. This study presents the use of the first derivative (velocity) of evoked dopamine signals as an alternative approach for measuring and distinguishing dopamine release from clearance. Maximal upward velocity predicts reductions in dopamine peak height due to D2 and GABAB receptor stimulation and by alterations in calcium concentrations. The Michaelis-Menten maximal velocity (Vmax) measure, an approximation for DAT levels, predicts maximal downward velocity in slices and in vivo. Dopamine peak height and upward velocity were similar between wild-type and DAT knock-out (DATKO) mice. In contrast, downward velocity was lower and exponential decay (tau) was higher in DATKO mice, supporting the use of both measures for extreme changes in DAT activity. In slices, the competitive DAT inhibitors cocaine, PTT, and WF23 increased peak height and upward velocity differentially across increasing concentrations, with PTT and cocaine reducing these measures at high concentrations. Downward velocity and tau values decreased and increased respectively across concentrations, with greater potency and efficacy observed with WF23 and PTT. In vivo recordings demonstrated similar effects of WF23, PTT, and cocaine on measures of release and clearance. Tau was a more sensitive measure at low concentrations, supporting its use as a surrogate for the Michaelis-Menten measure of apparent affinity (Km). Together, these results inform on the use of these various measures for dopamine release and clearance.
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Cocaína , Dopamina , Animales , Cocaína/farmacología , Cuerpo Estriado/metabolismo , Dopamina/farmacología , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Inhibidores de Captación de Dopamina/farmacología , Ratones , Ratas , Ratas Sprague-DawleyRESUMEN
BACKGROUND: Dopamine neuron firing in the ventral tegmental area (VTA) and dopamine release in the nucleus accumbens have been implicated in reward learning. Ethanol is known to increase both dopamine neuron firing in the VTA and dopamine levels in the nucleus accumbens. Despite this, some discrepancies exist between the dose of ethanol required to enhance firing in vivo and ex vivo. In the present study we investigated the effects of peripheral dopamine 2 subtype receptor antagonism on ethanol's effects on dopamine neurotransmission. METHODS: Plasma catecholamine levels were assessed following ethanol administration across four different doses of EtOH. Microdialysis and voltammetry were used to assess the effects of domperidone pretreatment on ethanol-mediated increases in dopamine release in the nucleus accumbens. A place conditioning paradigm was used to assess conditioned preference for ethanol and whether domperidone pretreatment altered this preference. Open-field and loss-of-righting reflex paradigms were used to assess the effects of domperidone on ethanol-induced sedation. A rotarod apparatus was used to assess the effects of domperidone on ethanol-induced motor impairment. RESULTS: Domperidone attenuated ethanol's enhancement of mesolimbic dopamine release under non-physiological conditions at intermediate (1.0 and 2.0 g/kg) doses of ethanol. Domperidone also decreased EtOH-induced sedation at 2.0 g/kg. Domperidone did not alter ethanol conditioned place preference nor did it affect ethanol-induced motor impairment. CONCLUSIONS: These results show that peripheral dopamine 2 receptors mediate some of the effects of ethanol on nonphysiological dopamine neurotransmission, although these effects are not related to the rewarding properties of ethanol.
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Dopamina , Núcleo Accumbens , Domperidona/farmacología , Etanol/farmacología , Área Tegmental VentralRESUMEN
Methamphetamine (MA) abuse remains a public health issue. Prenatal MA exposure (PME) poses a significant health problem, as we know very little about the drug's long-term physiological impact on the developing human brain. We investigated the long-term consequences of early MA exposure using a mouse model that targets the brain growth spurt, which occurs during human third-trimester. Adult mice previously subjected to acute MA during post-natal days 4-9 exhibited hyperactivity during the Open-Field Test, while exhibiting no motor coordination changes during the Rotarod Test. Neonatal MA exposure reduced basal dopamine (DA) uptake rates in adult nucleus accumbens slices compared with saline-injected controls. Although slices from neonatal MA-exposed mice showed no change in evoked DA signals in the presence of MA, they exhibited potentiated non-evoked DA release through DA efflux in response to MA. These data suggest that developmental MA exposure alters brain development to produce long-lasting physiological changes to the adult mesolimbic DA system, as well as altering responses to acute MA exposure in adulthood. This study provides new insights into an important, under-investigated area in drugs of abuse research.
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Metanfetamina , Adulto , Animales , Encéfalo , Dopamina , Femenino , Humanos , Núcleo Accumbens , Embarazo , Prueba de Desempeño de Rotación con Aceleración ConstanteRESUMEN
Previous studies indicate that moderate-to-high ethanol (EtOH) concentrations enhance dopamine (DA) neurotransmission in the mesolimbic DA system from the ventral tegmental area (VTA) and projecting to the nucleus accumbens core (NAc). However, voltammetry studies demonstrate that moderate-to-high EtOH concentrations decrease evoked DA release at NAc terminals. The involvement of γ-aminobutyric acid (GABA) receptors (GABAA Rs), glycine (GLY) receptors (GLYRs) and cholinergic interneurons (CINs) in mediating EtOH inhibition of evoked NAc DA release were examined. Fast scan cyclic voltammetry, electrophysiology, optogenetics and immunohistochemistry techniques were used to evaluate the effects of acute and chronic EtOH exposure on DA release and CIN activity in C57/BL6, CD-1, transgenic mice and δ-subunit knockout (KO) mice (δ-/-). Ethanol decreased DA release in mice with an IC50 of 80 mM ex vivo and 2.0 g/kg in vivo. GABA and GLY decreased evoked DA release at 1-10 mM. Typical GABAA R agonists inhibited DA release at high concentrations. Typical GABAA R antagonists had minimal effects on EtOH inhibition of evoked DA release. However, EtOH inhibition of DA release was blocked by the α4 ß3 δ GABAA R antagonist Ro15-4513, the GLYR antagonist strychnine and by the GABA ρ1 (Rho-1) antagonist TPMPA (10 µM) and reduced significantly in GABAA R δ-/- mice. Rho-1 expression was observed in CINs. Ethanol inhibited GABAergic synaptic input to CINs from the VTA and enhanced firing rate, both of which were blocked by TPMPA. Results herein suggest that EtOH inhibition of DA release in the NAc is modulated by GLYRs and atypical GABAA Rs on CINs containing δ- and Rho-subunits.
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Dopamina/metabolismo , Etanol/farmacología , Núcleo Accumbens/efectos de los fármacos , Receptores de GABA/efectos de los fármacos , Animales , Agonistas del GABA/farmacología , Antagonistas del GABA/farmacología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones TransgénicosRESUMEN
Striatal dopamine release is key for learning and motivation and is composed of subregions including the dorsal striatum (DS), nucleus accumbens core, and the nucleus accumbens shell. Spontaneously occurring dopamine release was compared across these subregions. Dopamine release/uptake dynamics differ across striatal subregions, with dopamine transient release amplitude and release frequency greatest in male mice, and the largest signals observed in the DS. Surprisingly, female mice exhibited little regional differences in dopamine release for DS and nucleus accumbens core regions, but lower release in the nucleus accumbens shell. Blocking voltage-gated K+ channel (Kv channels) with 4-aminopyridine enhanced dopamine detection without affecting reuptake. The 4-aminopyridine effects were greatest in ventral regions of female mice, suggesting regional differences in Kv channel expression. The dopamine transporter blocker cocaine also enhanced detection across subregions in both sexes, with greater overall increased release in females than males. Thus, sex differences in dopamine transmission are apparent and likely include differences in the Kv channel and dopamine transporter function. The lack of regional differences in dopamine release observed in females indicates differential regulation of spontaneous and evoked dopamine release.
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Cocaína , Dopamina , 4-Aminopiridina/metabolismo , Animales , Cocaína/metabolismo , Cocaína/farmacología , Cuerpo Estriado/metabolismo , Dopamina/metabolismo , Antagonistas de Dopamina , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Femenino , Masculino , Ratones , Núcleo Accumbens/metabolismo , Caracteres SexualesRESUMEN
Dopamine (DA) transmission plays a critical role in processing rewarding and pleasurable stimuli. Increased synaptic DA release in the nucleus accumbens (NAc) is a central component of the physiological effects of drugs of abuse. The essential trace element selenium mitigates methamphetamine-induced neurotoxicity. Selenium can also alter DA production and turnover. However, studies have not directly addressed the role of selenium in DA neurotransmission. Selenoprotein P (SELENOP1) requires selenium for synthesis and transports selenium to the brain, in addition to performing other functions. We investigated whether SELENOP1 directly impacts (1) DA signaling and (2) the dopaminergic response to methamphetamine. We used fast-scan cyclic voltammetry to investigate DA transmission and the response to methamphetamine in NAc slices from C57/BL6J SELENOP1 KO mice. Recordings from SELENOP1 KO mouse slices revealed reduced levels of evoked DA release and slower DA uptake rates. Methamphetamine caused a dramatic increase in vesicular DA release in SELENOP1 KO mice not observed in wild-type controls. This elevated response was attenuated by SELENOP1 application through a selenium-independent mechanism involving SELENOP1-apolipoprotein E receptor 2 (ApoER2) interaction to promote dopamine D2 receptor (D2R) function. In wild-type mice, increased vesicular DA release in response to methamphetamine was revealed by blocking D2R activation, indicating that the receptor suppresses the methamphetamine-induced vesicular increase. Our data provide evidence of a direct physiological role for SELENOP1 in the dopaminergic response to methamphetamine and suggest a signaling role for the protein in DA transmission.
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Parkinson's disease is associated with degeneration of neuromelanin (NM)-containing substantia nigra dopamine (DA) neurons and subsequent decreases in striatal DA transmission. Dopamine spontaneously forms a melanin through a process called melanogenesis. The present study examines conditions that promote/prevent DA melanogenesis. The kinetics, intermediates, and products of DA conversion to melanin in vitro, and DA melanogenesis under varying levels of Fe3+, pro-oxidants, and antioxidants were examined. The rate of melanogenesis for DA was substantially greater than related catecholamines norepinephrine and epinephrine and their precursor amino acids tyrosine and l-Dopa as measured by UV-IR spectrophotometry. Dopamine melanogenesis was concentration dependent on the pro-oxidant species and Fe3+. Melanogenesis was enhanced by the pro-oxidant hydrogen peroxide (EC50 = 500 µM) and decreased by the antioxidants ascorbate (IC50 = 10 µM) and glutathione (GSH; IC50 = 5 µM). Spectrophotometric results were corroborated by tuning a fast-scan cyclic voltammetry system to monitor DA melanogenesis. Evoked DA release in striatal brain slices resulted in NM formation that was prevented by GSH. These findings suggest that DA melanogenesis occurs spontaneously under physiologically-relevant conditions of oxidative stress and that NM may act as a marker of past exposure to oxidative stress.
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Alcohol misuse and dependence is a widespread health problem. The central nucleus of the amygdala (CeA) plays important roles in both the anxiety associated with alcohol (ethanol) dependence and the increased alcohol intake that is observed during withdrawal in dependent animals. We and others have shown the essential involvement of the corticotropin releasing factor (CRF) system in alcohol's synaptic effects on the CeA and in the development of ethanol dependence. Another system that has been shown to be critically involved in the molecular underpinnings of alcohol dependence is the norepinephrine (NE) system originating in the locus coeruleus. Both the CRF and NE systems act in concert to facilitate a stress response: central amygdalar afferents release CRF in the locus coeruleus promoting widespread release of NE. In this study, we are the first to use fast-scan cyclic voltammetry to classify local electrically-evoked NE release in the CeA and to determine if acute alcohol and CRF modulate it. Evoked NE release is action potential dependent, is abolished after depletion of monoaminergic vesicles, differs pharmacologically from dopamine release, is insensitive to acute alcohol, and decreases in response to locally applied CRF. Taken together, these results indicate that NE release in the CeA is released canonically in a vesicular-dependent manner, and that while acute alcohol does not directly alter NE release, CRF decreases it. Our results suggest that CRF acts locally on NE terminals as negative feedback and potentially prevents hyperactivation of the CRF-norepinephrine stress pathway.
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Núcleo Amigdalino Central/efectos de los fármacos , Núcleo Amigdalino Central/metabolismo , Hormona Liberadora de Corticotropina/farmacología , Etanol/farmacología , Norepinefrina/metabolismo , Animales , Masculino , Norepinefrina/antagonistas & inhibidores , Técnicas de Cultivo de Órganos , Ratas , Ratas Sprague-DawleyRESUMEN
RATIONALE: Methamphetamine (METH) enhances exocytotic dopamine (DA) signals and induces DA transporter (DAT)-mediated efflux in brain striatal regions such as the nucleus accumbens (NAc). Blocking sigma receptors prevents METH-induced DA increases. Sigma receptor activation induces Ca2+ release from intracellular stores, which may be responsible for METH-induced DA increases. OBJECTIVES: The role of intracellular and extracellular Ca2+ in METH-induced DA increases and associated behavior was tested. METHODS: METH-induced Ca2+ release was measured in hNPC-derived DA cells using ratiometric Ca2+ imaging. In mouse brain slices, fast-scan cyclic voltammetry was used to measure METH effects on two measures of dopamine: electrically stimulated and DAT-mediated efflux. Intracellular and extracellular Ca2+ was removed through pharmacological blockade of Ca2+ permeable channels (Cd2+ and IP3 sensitive channels), intracellular Ca2+ chelation (BAPTA-AM), or non-inclusion (zero Ca2+). Lastly, METH effects on dopamine-mediated locomotor behavior were tested in rats. Rats received intra-NAc injections of ACSF or 2-aminoethoxydiphenyl borate (2-APB; IP3 receptor blocker) and intraperitoneal METH (5 mg/kg) to test the role of intracellular Ca2+ release in DA-mediated behaviors. RESULTS: Reducing Ca2+ extracellular levels and Ca2+ release from intracellular stores prevented intracellular Ca2+ release. Intracellular Ca2+ chelation and blocking intracellular Ca2+ release reduced METH effects on voltammetric measures of dopamine. Blocking intracellular Ca2+ release via 2-APB resulted in increased METH-induced circling behavior. CONCLUSIONS: METH induces NAc DA release through intracellular Ca2+ activity. Blocking intracellular Ca2+ release prevents METH effects on DA signals and related behavior.