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Optineurin (OPTN) mutations are linked to amyotrophic lateral sclerosis (ALS) and normal tension glaucoma (NTG), but a relevant animal model is lacking, and the molecular mechanisms underlying neurodegeneration are unknown. We found that OPTN C-terminus truncation (OPTN∆C) causes late-onset neurodegeneration of retinal ganglion cells (RGCs), optic nerve (ON), and spinal cord motor neurons, preceded by a striking decrease of axonal mitochondria. Surprisingly, we discover that OPTN directly interacts with both microtubules and the mitochondrial transport complex TRAK1/KIF5B, stabilizing them for proper anterograde axonal mitochondrial transport, in a C-terminus dependent manner. Encouragingly, overexpressing OPTN/TRAK1/KIF5B reverses not only OPTN truncation-induced, but also ocular hypertension-induced neurodegeneration, and promotes striking ON regeneration. Therefore, in addition to generating new animal models for NTG and ALS, our results establish OPTN as a novel facilitator of the microtubule-dependent mitochondrial transport necessary for adequate axonal mitochondria delivery, and its loss as the likely molecular mechanism of neurodegeneration.
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Psychological stressors, like the nearby presence of a predator, can be strong enough to induce physiological/hormonal alterations, leading to appetite changes. However, little is known about how threats can alter feeding-related hypothalamic circuit functions. Here, we found that proenkephalin (Penk)-expressing lateral hypothalamic (LHPenk) neurons of mice exposed to predator scent stimulus (PSS) show sensitized responses to high-fat diet (HFD) eating, whereas silencing of the same neurons normalizes PSS-induced HFD overconsumption associated with a negative emotional state. Downregulation of endogenous enkephalin peptides in the LH is crucial for inhibiting the neuronal and behavioral changes developed after PSS exposure. Furthermore, elevated corticosterone after PSS contributes to enhance the reactivity of glucocorticoid receptor (GR)-containing LHPenk neurons to HFD, whereas pharmacological inhibition of GR in the LH suppresses PSS-induced maladaptive behavioral responses. We have thus identified the LHPenk neurons as a critical component in the threat-induced neuronal adaptation that leads to emotional overconsumption.
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Área Hipotalámica Lateral , Neuronas , Ratones , Animales , Área Hipotalámica Lateral/fisiología , Neuronas/fisiología , Encefalinas/genética , HiperfagiaRESUMEN
Early-life trauma (ELT) is a risk factor for binge eating and obesity later in life, yet the neural circuits that underlie this association have not been addressed. Here, we show in mice that downregulation of the leptin receptor (Lepr) in the lateral hypothalamus (LH) and its effect on neural activity is crucial in causing ELT-induced binge-like eating and obesity upon high-fat diet exposure. We also found that the increased activity of Lepr-expressing LH (LHLepr) neurons encodes sustained binge-like eating in ELT mice. Inhibition of LHLepr neurons projecting to the ventrolateral periaqueductal gray normalizes these behavioral features of ELT mice. Furthermore, activation of proenkephalin-expressing ventrolateral periaqueductal gray neurons, which receive inhibitory inputs from LHLepr neurons, rescues ELT-induced maladaptive eating habits. Our results identify a circuit pathway that mediates ELT-induced maladaptive eating and may lead to the identification of novel therapeutic targets for binge eating and obesity.
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Área Hipotalámica Lateral , Leptina , Ratones , Animales , Leptina/metabolismo , Área Hipotalámica Lateral/metabolismo , Conducta Alimentaria , Obesidad/metabolismo , Sustancia Gris Periacueductal , Receptores de Leptina/genética , Receptores de Leptina/metabolismo , Ingestión de AlimentosRESUMEN
Modafinil, a psychostimulant, is used in the treatment of narcolepsy, shift work sleep disorder, and excessive daytime sleepiness associated with obstructive sleep apnea. Preclinical and clinical studies suggest that modafinil may have reinforcing effects. However, a possible rewarding property of modafinil has not been fully investigated. In this study, we assessed the potential rewarding property of modafinil using the conditioned place preference (CPP) paradigm in mice. Using radiolabeled ligands, we observed changes in dopamine, glutamate, and GABA receptor binding in the brains of mice after treatment with modafinil. Modafinil produced significant CPP in mice at an intraperitoneal (i.p.) dose of 125 mg kg⻹ and prevented normal body weight gain of mice in a dose-dependent manner. A significant reduction in normal body weight gain was observed when mice were administrated 125 mg kg⻹ modafinil. In addition, there were widespread changes in receptor binding in the brains of modafinil-treated mice; Dopamine D1 binding was increased in the caudate putamen, the accumbens, and the substantia nigra, while dopamine D2 binding was decreased in the caudate putamen and the accumbens. Dopamine transporter (DAT) binding was increased in the prefrontal cortex, the caudate putamen, and the nucleus accumbens. No changes were observed in NMDA and GABA(A) receptor binding. These data indicate that modafinil had a significant rewarding property and could be abused as a recreational drug. Dopamine systems may play a key role in the rewarding property of modafinil.
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Compuestos de Bencidrilo/farmacología , Encéfalo/efectos de los fármacos , Estimulantes del Sistema Nervioso Central/farmacología , Condicionamiento Psicológico/efectos de los fármacos , Animales , Autorradiografía , Peso Corporal/efectos de los fármacos , Encéfalo/metabolismo , Dopamina/metabolismo , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática/metabolismo , Masculino , Ratones , Ratones Endogámicos ICR , Modafinilo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismoRESUMEN
The nucleus accumbens (NAc) is a forebrain region mediating the positive-reinforcing properties of drugs of abuse, including alcohol. It receives glutamatergic projections from multiple forebrain and limbic regions such as the prefrontal cortex (PFCx) and basolateral amygdala (BLA), respectively. However, it is unknown how NAc medium spiny neurons (MSNs) integrate PFCx and BLA inputs, and how this integration is affected by alcohol exposure. Because progress has been hampered by the inability to independently stimulate different pathways, we implemented a dual wavelength optogenetic approach to selectively and independently stimulate PFCx and BLA NAc inputs within the same brain slice. This approach functionally demonstrates that PFCx and BLA inputs synapse onto the same MSNs where they reciprocally inhibit each other pre-synaptically in a strict time-dependent manner. In alcohol-naïve mice, this temporal gating of BLA-inputs by PFCx afferents is stronger than the reverse, revealing that MSNs prioritize high-order executive processes information from the PFCx. Importantly, binge alcohol drinking alters this reciprocal inhibition by unilaterally strengthening BLA inhibition of PFCx inputs. In line with this observation, we demonstrate that in vivo optogenetic stimulation of the BLA, but not PFCx, blocks binge alcohol drinking escalation in mice. Overall, our results identify NAc MSNs as a key integrator of executive and emotional information and show that this integration is dysregulated during binge alcohol drinking.
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PURPOSE: The transient receptor potential vanilloid 1 (TRPV1) is a nonselective cation channel that mediates synaptic modification in the nucleus accumbens (NAc). However, no study has yet examined the mechanism of TRPV1 in the NAc on cocaine reinstatement. We investigated the mechanism of TRPV1 in NAc on cocaine reinstatement using the conditioned place preference (CPP) test in mice. METHODS: We examined the effect of capsazepine (5 mg/kg, a TRPV1 antagonist, administered intraperitoneally (i.p.)), capsaicin (0.3 mg/kg, a TRPV1 agonist, administered i.p.), and genetic deletion of TRPV1 on the reinstatement of cocaine-induced CPP (15 mg/kg, administered i.p.). The expression of TRPV1 and Ca2+/calmodulin-mediated kinase II (CaMKII) in the NAc were determined after cocaine reinstatement. Microinjection of SB366791 (0.2 ng, a selective TRPV1 antagonist) in the NAc was assessed on SKF-81297 (1 µg, D1-like dopamine (DA) receptor agonist) primed cocaine reinstatement. RESULTS: Capsazepine suppressed and capsaicin potentiated cocaine CPP in the reinstatement phase. In addition, genetic deletion of TRPV1 inhibited cocaine-priming reinstatement. Cocaine reinstatement was mediated by increased TRPV1 expression in the NAc, which involves CaMKII. Microinjection of SB366791 in the NAc prevented the cocaine reinstatement evoked by microinjection of SKF-81297 in the NAc. CONCLUSIONS: These findings suggest that activation of TRPV1 mediates the stimulation of D1-like DA receptors and CaMKII in the NAc, resulting in the facilitation of cocaine reinstatement behaviors. Thus, our findings reveal a previously unknown TRPV1 mechanism in the reinstatement to drugs of abuse.
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Cocaína/administración & dosificación , Condicionamiento Psicológico/efectos de los fármacos , Receptores de Dopamina D1/metabolismo , Canales Catiónicos TRPV/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Benzazepinas/farmacología , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Capsaicina/análogos & derivados , Capsaicina/farmacología , Cocaína/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Núcleo Accumbens/efectos de los fármacos , Canales Catiónicos TRPV/genéticaRESUMEN
Cocaine addiction and depression are comorbid disorders. Although it is well recognized that 5-hydroxytryptamine (5-HT; serotonin) plays a central role in depression, our understanding of its role in addiction is notably lacking. The 5-HT system in the brain is carefully controlled by a combined process of regulating 5-HT neuron firing through 5-HT autoreceptors, neurotransmitter release, enzymatic degradation, and reuptake by transporters. This study tests the hypothesis that activation of 5-HT1A autoreceptors, which would lessen 5-HT neuron firing, contributes to cocaine-seeking behaviors. Using 5-HT neuron-specific reduction of 5-HT1A autoreceptor gene expression in mice, we demonstrate that 5-HT1A autoreceptors are necessary for cocaine conditioned place preference. In addition, using designer receptors exclusively activated by designer drugs (DREADDs) technology, we found that stimulation of the serotonergic dorsal raphe nucleus (DRN) afferents to the nucleus accumbens (NAc) abolishes cocaine reward and promotes antidepressive-like behaviors. Finally, using a rat model of compulsive-like cocaine self-administration, we found that inhibition of dorsal raphe 5-HT1A autoreceptors attenuates cocaine self-administration in rats with 6 h extended access, but not 1 h access to the drug. Therefore, our findings suggest an important role for 5-HT1A autoreceptors, and thus DRNî²NAc 5-HT neuronal activity, in the etiology and vulnerability to cocaine reward and addiction. Moreover, our findings support a strategy for antagonizing 5-HT1A autoreceptors for treating cocaine addiction.
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Cocaína/administración & dosificación , Conducta Compulsiva/fisiopatología , Núcleo Dorsal del Rafe/fisiopatología , Comportamiento de Búsqueda de Drogas/fisiología , Receptor de Serotonina 5-HT1A/fisiología , Neuronas Serotoninérgicas/fisiología , Animales , Autorreceptores/antagonistas & inhibidores , Autorreceptores/fisiología , Condicionamiento Clásico/efectos de los fármacos , Condicionamiento Clásico/fisiología , Drogas de Diseño/administración & dosificación , Núcleo Dorsal del Rafe/efectos de los fármacos , Comportamiento de Búsqueda de Drogas/efectos de los fármacos , Técnicas de Silenciamiento del Gen , Masculino , Ratones , Motivación/efectos de los fármacos , Motivación/fisiología , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/fisiopatología , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/fisiopatología , Ratas , Ratas Wistar , Receptor de Serotonina 5-HT1A/genética , Recompensa , Neuronas Serotoninérgicas/efectos de los fármacos , Antagonistas del Receptor de Serotonina 5-HT1/administración & dosificaciónRESUMEN
RATIONALE: Phentermine is structurally similar to methamphetamine and is widely used as an anti-obesity drug in the USA and many other countries. The potential for reward of phentermine has been noted; however, the mechanisms of phentermine dependence have not been established. OBJECTIVES: Here, we investigated the rewarding and dopaminergic behavioral responses to phentermine in mice and found that phentermine produced conditioned rewarding effects through the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in the nucleus accumbens (NAc). METHODS: The impact of phentermine was assessed using conditioned place preference (CPP) test, climbing behavior test, and western blot analysis. RESULTS: Phentermine 1 and 3 mg/kg (i.p.) significantly increased CPP. Phentermine, a known dopamine releaser, boosted apomorphine-induced climbing behavior in mice, and methamphetamine (i.p.) also increased apomorphine-induced dopaminergic behavior. Phentermine and methamphetamine increased the level of expression of the dopamine transporter (DAT) and phospho-Akt proteins to a similar degree in the NAc of CPP mice. To determine whether the conditioned rewarding effects of phentermine were mediated through the PI3K/Akt pathway, we assessed the effects of the Akt inhibitor LY294002 on phentermine-induced place preference and climbing behavior. LY294002 (1 and 3 µg/site, i.c.v.) reduced phentermine-induced CPP and phentermine-increased climbing behavior. However, LY294002 did not change CPP and climbing behavior itself and also did not decrease apomorphine-induced climbing behavior in mice. Further, LY294002 decreased the phentermine-increased levels of DAT protein and phosphorylation of Akt in the NAc of CPP mice. CONCLUSIONS: Thus, these findings suggest that phentermine induces conditioned rewarding effects via activation of the PI3K/Akt signaling pathway in the NAc.
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Condicionamiento Psicológico/fisiología , Núcleo Accumbens/metabolismo , Proteína Oncogénica v-akt/metabolismo , Fentermina/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Recompensa , Animales , Fármacos Antiobesidad/farmacología , Apomorfina/farmacología , Condicionamiento Psicológico/efectos de los fármacos , Dopamina/metabolismo , Relación Dosis-Respuesta a Droga , Masculino , Metanfetamina/farmacología , Ratones , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Núcleo Accumbens/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiologíaRESUMEN
Oxethazaine, an over-the-counter (OTC) antacid, is a precursor of phentermine, which is the most abused anorectic by methamphetamine users in Korea. However, no studies have investigated the abuse potential of oxethazaine. Therefore, we examined and compared the consequences of oxethazaine and phentermine treatment on animal models of conditioned place preference (CPP) and self-administration. Furthermore, oxethazaine and its metabolites in rat plasma were monitored using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after oxethazaine administration, and compared with phentermine itself after phentermine administration to clarify the relationship between phentermine production by oxethazaine ingestion and the possible oxethazaine dependence. Oxethazaine metabolites were also determined by LC-MS/MS in rat hair after oxethazaine administration to investigate the possibility of phentermine detection in hair from oxethazaine abusers. In the behavioral experiment, phentermine (3mg/kg) produced CPP in mice while oxethazaine (5, 10, and 15mg/kg) did not. Moreover, phentermine (0.25mg/kg/infusion) was self-administered by rats at 80% of free-feeding weight, whereas oxethazaine was not. In the analytical study, mephentermine and phentermine, both oxethazaine metabolites, were detected below the limit of quantitation or not detected in both plasma and hair from rats that had ingested oxethazaine (10mg/kg, single dose or for 2weeks). On the other hand, phentermine was detected in plasma and hair samples from rats that had ingested phentermine (10mg/kg, single dose or for 2weeks). Consequently, phentermine induced significant rewarding effects, but oxethazaine did not. Presumably, either oxethazaine does not have any abuse potential or oxethazaine metabolism to phentermine does not result in a pharmacologically active level of psychostimulant in the body. Furthermore, phentermine was not a major metabolite in hair obtained from oxethazaine abusers, which should make it possible to differentiate between chronic oxethazaine and phentermine users.
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Anestésicos Locales/toxicidad , Etanolaminas/toxicidad , Cabello/química , Drogas Ilícitas/toxicidad , Modelos Animales , Motivación , Anestésicos Locales/análisis , Anestésicos Locales/sangre , Animales , Cromatografía Liquida , Etanolaminas/análisis , Etanolaminas/sangre , Drogas Ilícitas/análisis , Drogas Ilícitas/sangre , Masculino , Ratas , Ratas Wistar , Ratas Zucker , Espectrometría de Masas en TándemRESUMEN
The transient receptor potential vanilloid type 1 channel (TRPV1) receptors are expressed in various regions of the brain. Much less is known about whether TRPV1 receptors affect higher brain functions. In the present study, we demonstrated that TRPV1-knockout (TRPV1KO) mice showed antidepressant-like behaviors in a novelty-suppressed feeding test and forced swim test when compared to wild-type (WT) mice. Additionally, TRPV1KO mice exhibited increased aggressiveness and reduced social interactions in a social dominance test and social interaction test. TRPV1KO mice showed reduced short-term memory and normal long-term memory in a novel object recognition test and passive avoidance test versus WT mice. Based on these behavioral data, we investigated changes in specific receptors related to depression, anxiety, and memory in the brains of TRPV1KO and WT mice. Binding of [(3)H]-8-OH-DPAT was significantly higher in the frontal associated cortex (FrA), nucleus accumbens (NAc), and the cingulate cortex (CC) of TRPV1KO mice than WT mice, while the expression of 5-HT(1A) receptors was higher in the FrA, NAc, and cortex of TRPV1KO mice than WT mice. [(3)H]-flunitrazepam binding was also significantly higher in the FrA, striatum (CPU), and the CC of TRPV1KO versus WT mice. In contrast, [(3)H]-musicmol binding in the FrA, CPU, NAc, CC, and the dentate gyrus (DG) was significantly lower in TRPV1KO mice than WT mice. The expression of GABA(A)γ(2) was higher in the NAc, CPU, and cortex of TRPV1KO versus WT mice, whereas the expression of GABA(A)α(2) was lower in the FrA, CPU, NAc, and cortex in TRPV1KO mice than WT mice. Finally, [(3)H]-MK-801 binding was decreased in the CPU and CA1 of TRPV1KO versus WT mice. The expression of NR2A was lower in the hippocampus of TRPV1KO versus WT mice. These data suggest that the loss of TRPV1 results in antidepressant-like, anxiolytic, abnormal social and reduced memorial behaviors due to changes in expression of 5-HT(1A), GABA(A,) and NMDA receptors. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.
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Encéfalo/metabolismo , Emociones/fisiología , Memoria/fisiología , Receptor de Serotonina 5-HT1A/metabolismo , Receptores de GABA-A/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Canales Catiónicos TRPV/metabolismo , Animales , Reacción de Prevención/fisiología , Conducta Animal/fisiología , Dominación-Subordinación , Ratones , Ratones Noqueados , Fenotipo , Receptor de Serotonina 5-HT1A/genética , Receptores de GABA-A/genética , Receptores de N-Metil-D-Aspartato/genética , Canales Catiónicos TRPV/genéticaRESUMEN
ETHNOPHARMACOLOGICAL RELEVANCE: Eucommia ulmoides Oliv. Bark. (EUE), has commonly been used to fortify the muscles and lungs, lower blood pressure, prevent miscarriage, improve the tone of liver and kidneys, and promote longevity the traditional tonic medicines of Korea, China, and Japan. AIM OF THE STUDY: In this study, we investigated that the neuroprotective activities and possible mechanisms of EUE aqueous extract in hydrogen peroxide (H(2)O(2))-induced neuronal cell death in human SH-SY5Y neuroblastoma cells. MATERIAL AND METHOD: We examined the effects of EUE against H(2)O(2)-induced cytotoxicity, DNA condensation, the production of reactive oxygen species (ROS), loss of mitochondria membrane potential (MMP), the proteolysis of cleaved poly-ADP-ribose polymerase (PARP), and the expression of Bcl-2, Bcl-xL, cleaved caspase-3, and release of cytochrome c. Moreover, we attempted to determine whether EUE suppressed the phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK 1/2), and phosphoinositide 3-kinase (PI3K)/Akt. RESULTS: Pretreatment with EUE increased cell viability and inhibited cytotoxicity and DNA condensation. EUE also attenuated the increase in ROS production and MMP reduction. Western blot data revealed that EUE inhibited H(2)O(2)-induced up- or down-regulation of cleaved PARP, cleaved caspase-3, Bcl-2, and Bcl-xL. The EUE inhibited release of cytochrome c from mitochondria to the cytosol, and significantly attenuated H(2)O(2)-induced phosphorylation of JNK, p38 MAPK, ERK 1/2, and PI3K/Akt. CONCLUSION: The potent neuroprotective capacity of EUE, shown in these experiments, may potentially be applied in the prevention or treatment of neurodegenerative diseases such as Alzheimer's disease (AD).
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Antioxidantes/farmacología , Muerte Celular/efectos de los fármacos , Eucommiaceae , Enfermedades Neurodegenerativas , Neuronas/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Extractos Vegetales/farmacología , Antioxidantes/uso terapéutico , Transporte Biológico/efectos de los fármacos , Caspasa 3/metabolismo , Línea Celular , Supervivencia Celular/efectos de los fármacos , Citocromos c/metabolismo , Citosol/efectos de los fármacos , ADN/efectos de los fármacos , Humanos , Peróxido de Hidrógeno , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Enfermedades Neurodegenerativas/tratamiento farmacológico , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/metabolismo , Neuronas/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Fosforilación , Fitoterapia , Extractos Vegetales/uso terapéutico , Poli(ADP-Ribosa) Polimerasas/metabolismo , Proteolisis , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
Dimenhydrinate (DIM) is an over-the-counter antihistamine consisting of diphenhydramine (DIP) and 8-chlorotheophylline (CTP). Medical use of DIM is for prevention of nausea and motion sickness. Recently, it has been reported that DIM may be used alone or in combination with other drugs for recreational purposes due to its euphoric and hallucinogenic effects. To investigate the putatively rewarding properties of DIM and its constituents DIP and CTP, we used a conditioned place preference (CPP) test in mice. DIM significantly induced CPP at a dose of 30 mg/kg. Neither DIP (3, 10, and 30 mg/kg) nor CTP (3, 10, and 30 mg/kg) alone induced CPP. Because neither DIP nor CTP resulted in CPP, the rewarding property of DIM appears to be caused by the sum of the effects of its constituents. In addition, low doses of DIM (3 mg/kg), co-administered with low doses of cocaine (7.5 mg/kg), significantly induced CPP, while neither low-dose DIM (3 mg/kg) nor low-dose cocaine (7.5 mg/kg) administered separately induced CPP. This result suggests the liability of DIM use in combination with other abused drugs to create a stronger effect.
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Conducta de Elección/efectos de los fármacos , Condicionamiento Psicológico/efectos de los fármacos , Dimenhidrinato/efectos adversos , Recompensa , Animales , Cocaína/farmacología , Difenhidramina/efectos adversos , Relación Dosis-Respuesta a Droga , Sinergismo Farmacológico , Masculino , Ratones , Ratones Endogámicos ICR , Teofilina/efectos adversos , Teofilina/análogos & derivadosRESUMEN
Butorphanol is a synthetic opioid agonist/antagonist analgesic agent that mainly exerts its effects through kappa-opioid receptors. It has been demonstrated that kappa-opioid receptors preferentially mediate the development of physical dependence upon butorphanol and the associated withdrawal syndrome. However, it is not fully understood whether or not nNOS-containing neurons in the various brain regions play an important role in butorphanol withdrawal. Therefore, this study was conducted to determine whether the selective nNOS inhibitor, 7-NI, modifies the development of butorphanol withdrawal and changes of nNOS expressions in different brain regions in physically butorphanol-dependent rats. The first part of the study focused on withdrawal behaviors in male Sprague-Dawley rats. Physical dependence was induced by a 72-h i.c.v. infusion with butorphanol (26 nmol/mixrol/h) and withdrawal was subsequently precipitated by i.c.v. challenge with naloxone (48 nmol/5 microl/rat) 2 h after termination of the butorphanol infusion. The butorphanol/7-NI coadministration group showed a significant decrease in several signs of withdrawal such as teeth chattering, as compared with the butorphanol-treated group. In the second part of the study, immunohistochemical analysis was performed to determine the expression of nNOS in the various brain regions. In the butorphanol/7-NI coadministration group, the number of cells labeled for nNOS was significantly lower in the various brain regions (including the caudate putamen, nucleus accumbens, and hippocampus) than in the butorphanol group. Therefore, 7-NI decreased in butorphanol-induced physical dependence and nNOS expression. Taken together, these findings suggest that the nNOS system is involved in the development of butorphanol-induced physical dependence, and 7-NI has potential clinical application as a candidate for the treatment of opioid withdrawal syndrome.