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1.
Br J Pharmacol ; 2024 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-38715413

RESUMEN

BACKGROUND AND PURPOSE: The voltage-gated sodium channel isoform NaV1.7 is a high-interest target for the development of non-opioid analgesics due to its preferential expression in pain-sensing neurons. NaV1.7 is also expressed in autonomic neurons, yet its contribution to involuntary visceral reflexes has received limited attention. The small molecule inhibitor ST-2560 was advanced into pain behaviour and cardiovascular models to understand the pharmacodynamic effects of selective inhibition of NaV1.7. EXPERIMENTAL APPROACH: Potency of ST-2560 at NaV1.7 and off-target ion channels was evaluated by whole-cell patch-clamp electrophysiology. Effects on nocifensive reflexes were assessed in non-human primate (NHP) behavioural models, employing the chemical capsaicin and mechanical stimuli. Cardiovascular parameters were monitored continuously in freely-moving, telemetered NHPs following administration of vehicle and ST-2560. KEY RESULTS: ST-2560 is a potent inhibitor (IC50 = 39 nM) of NaV1.7 in primates with ≥1000-fold selectivity over other isoforms of the human NaV1.x family. Following systemic administration, ST-2560 (0.1-0.3 mg·kg-1, s.c.) suppressed noxious mechanical- and chemical-evoked reflexes at free plasma concentrations threefold to fivefold above NaV1.7 IC50. ST-2560 (0.1-1.0 mg·kg-1, s.c.) also produced changes in haemodynamic parameters, most notably a 10- to 20-mmHg reduction in systolic and diastolic arterial blood pressure, at similar exposures. CONCLUSIONS AND IMPLICATIONS: Acute pharmacological inhibition of NaV1.7 is antinociceptive, but also has the potential to impact the cardiovascular system. Further work is merited to understand the role of NaV1.7 in autonomic ganglia involved in the control of heart rate and blood pressure, and the effect of selective NaV1.7 inhibition on cardiovascular function.

2.
Br J Pharmacol ; 181(7): 1028-1050, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-37698384

RESUMEN

BACKGROUND AND PURPOSE: Select neuroactive steroids tune neural activity by modulating excitatory and inhibitory neurotransmission, including the endogenous cholesterol metabolite 24(S)-hydroxycholesterol (24(S)-HC), which is an N-methyl-d-aspartate (NMDA) receptor positive allosteric modulator (PAM). NMDA receptor PAMs are potentially an effective pharmacotherapeutic strategy to treat conditions associated with NMDA receptor hypofunction. EXPERIMENTAL APPROACH: Using in vitro and in vivo electrophysiological recording experiments and behavioural approaches, we evaluated the effect of SAGE-718, a novel neuroactive steroid NMDA receptor PAM currently in clinical development for the treatment of cognitive impairment, on NMDA receptor function and endpoints that are altered by NMDA receptor hypoactivity and assessed its safety profile. KEY RESULTS: SAGE-718 potentiated GluN1/GluN2A-D NMDA receptors with equipotency and increased NMDA receptor excitatory postsynaptic potential (EPSP) amplitude without affecting decay kinetics in striatal medium spiny neurons. SAGE-718 increased the rate of unblock of the NMDA receptor open channel blocker ketamine on GluN1/GluN2A in vitro and accelerated the rate of return on the ketamine-evoked increase in gamma frequency band power, as measured with electroencephalogram (EEG), suggesting that PAM activity is driven by increased channel open probability. SAGE-718 ameliorated deficits due to NMDA receptor hypofunction, including social deficits induced by subchronic administration of phencyclidine, and behavioural and electrophysiological deficits from cholesterol and 24(S)-HC depletion caused by 7-dehydrocholesterol reductase inhibition. Finally, SAGE-718 did not produce epileptiform activity in a seizure model or neurodegeneration following chronic dosing. CONCLUSIONS AND IMPLICATIONS: These findings provide strong evidence that SAGE-718 is a neuroactive steroid NMDA receptor PAM with a mechanism that is well suited as a treatment for conditions associated with NMDA receptor hypofunction.


Asunto(s)
Ketamina , Neuroesteroides , Receptores de N-Metil-D-Aspartato/metabolismo , Ketamina/farmacología , Hidroxicolesteroles/farmacología , Colesterol , Regulación Alostérica
3.
Cell Mol Life Sci ; 80(2): 42, 2023 Jan 16.
Artículo en Inglés | MEDLINE | ID: mdl-36645496

RESUMEN

N-methyl-D-aspartate receptors (NMDARs) play vital roles in normal brain functions (i.e., learning, memory, and neuronal development) and various neuropathological conditions, such as epilepsy, autism, Parkinson's disease, Alzheimer's disease, and traumatic brain injury. Endogenous neuroactive steroids such as 24(S)-hydroxycholesterol (24(S)-HC) have been shown to influence NMDAR activity, and positive allosteric modulators (PAMs) derived from 24(S)-hydroxycholesterol scaffold can also enhance NMDAR function. This study describes the structural determinants and mechanism of action for 24(S)-hydroxycholesterol and two novel synthetic analogs (SGE-550 and SGE-301) on NMDAR function. We also show that these agents can mitigate the altered function caused by a set of loss-of-function missense variants in NMDAR GluN subunit-encoding GRIN genes associated with neurological and neuropsychiatric disorders. We anticipate that the evaluation of novel neuroactive steroid NMDAR PAMs may catalyze the development of new treatment strategies for GRIN-related neuropsychiatric conditions.


Asunto(s)
Enfermedad de Alzheimer , Enfermedades del Sistema Nervioso , Neuroesteroides , Humanos , Receptores de N-Metil-D-Aspartato/metabolismo , Neuroesteroides/farmacología , Neuroesteroides/uso terapéutico , Hidroxicolesteroles/farmacología , Hidroxicolesteroles/uso terapéutico , Enfermedades del Sistema Nervioso/tratamiento farmacológico , Enfermedades del Sistema Nervioso/genética , Enfermedad de Alzheimer/tratamiento farmacológico , Esteroides/farmacología , Regulación Alostérica/fisiología
4.
ACS Med Chem Lett ; 13(11): 1763-1768, 2022 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-36385936

RESUMEN

The voltage-gated sodium channel isoform NaV1.7 has drawn widespread interest as a target for non-opioid, investigational new drugs to treat pain. Selectivity over homologous, off-target sodium channel isoforms, which are expressed in peripheral motor neurons, the central nervous system, skeletal muscle and the heart, poses a significant challenge to the development of small molecule inhibitors of NaV1.7. Most inhibitors of NaV1.7 disclosed to date belong to a class of aryl and acyl sulfonamides that preferentially bind to an inactivated conformation of the channel. By taking advantage of a sequence variation unique to primate NaV1.7 in the extracellular pore of the channel, a series of bis-guanidinium analogues of the natural product, saxitoxin, has been identified that are potent against the resting conformation of the channel. A compound of interest, 25, exhibits >600-fold selectivity over off-target sodium channel isoforms and is efficacious in a preclinical model of acute pain.

5.
J Med Chem ; 65(13): 9063-9075, 2022 07 14.
Artículo en Inglés | MEDLINE | ID: mdl-35785990

RESUMEN

N-Methyl-d-aspartate receptor (NMDAR) positive allosteric modulators (PAMs) have received increased interest as a powerful mechanism of action to provide relief as therapies for CNS disorders. Sage Therapeutics has previously published the discovery of endogenous neuroactive steroid 24(S)-hydroxycholesterol as an NMDAR PAM. In this article, we detail the discovery of development candidate SAGE-718 (5), a potent and high intrinsic activity NMDAR PAM with an optimized pharmacokinetic profile for oral dosing. Compound 5 has completed phase 1 single ascending dose and multiple ascending dose clinical trials and is currently undergoing phase 2 clinical trials for treatment of cognitive impairment in Huntington's disease.


Asunto(s)
Enfermedades del Sistema Nervioso Central , Disfunción Cognitiva , Neuroesteroides , Regulación Alostérica , Disfunción Cognitiva/tratamiento farmacológico , Humanos , Receptores de N-Metil-D-Aspartato/metabolismo
6.
Pain ; 162(4): 1250-1261, 2021 04 01.
Artículo en Inglés | MEDLINE | ID: mdl-33086288

RESUMEN

ABSTRACT: The voltage-gated sodium channel Nav1.7 is highly expressed in nociceptive afferents and is critically involved in pain signal transmission. Nav1.7 is a genetically validated pain target in humans because loss-of-function mutations cause congenital insensitivity to pain and gain-of-function mutations cause severe pain syndromes. Consequently, pharmacological inhibition has been investigated as an analgesic therapeutic strategy. We describe a small molecule Nav1.7 inhibitor, ST-2530, that is an analog of the naturally occurring sodium channel blocker saxitoxin. When evaluated against human Nav1.7 by patch-clamp electrophysiology using a protocol that favors the resting state, the Kd of ST-2530 was 25 ± 7 nM. ST-2530 exhibited greater than 500-fold selectivity over human voltage-gated sodium channel isoforms Nav1.1-Nav1.6 and Nav1.8. Although ST-2530 had lower affinity against mouse Nav1.7 (Kd = 250 ± 40 nM), potency was sufficient to assess analgesic efficacy in mouse pain models. A 3-mg/kg dose administered subcutaneously was broadly analgesic in acute pain models using noxious thermal, mechanical, and chemical stimuli. ST-2530 also reversed thermal hypersensitivity after a surgical incision on the plantar surface of the hind paw. In the spared nerve injury model of neuropathic pain, ST-2530 transiently reversed mechanical allodynia. These analgesic effects were demonstrated at doses that did not affect locomotion, motor coordination, or olfaction. Collectively, results from this study indicate that pharmacological inhibition of Nav1.7 by a small molecule agent with affinity for the resting state of the channel is sufficient to produce analgesia in a range of preclinical pain models.


Asunto(s)
Canal de Sodio Activado por Voltaje NAV1.7 , Saxitoxina , Analgésicos/farmacología , Analgésicos/uso terapéutico , Animales , Ratones , Canal de Sodio Activado por Voltaje NAV1.7/genética , Canal de Sodio Activado por Voltaje NAV1.8/genética , Isoformas de Proteínas , Bloqueadores de los Canales de Sodio/farmacología , Bloqueadores de los Canales de Sodio/uso terapéutico
7.
J Med Chem ; 62(19): 8695-8710, 2019 10 10.
Artículo en Inglés | MEDLINE | ID: mdl-31012583

RESUMEN

Voltage-gated sodium ion channel subtype 1.7 (NaV1.7) is a high interest target for the discovery of non-opioid analgesics. Compelling evidence from human genetic data, particularly the finding that persons lacking functional NaV1.7 are insensitive to pain, has spurred considerable effort to develop selective inhibitors of this Na+ ion channel target as analgesic medicines. Recent clinical setbacks and disappointing performance of preclinical compounds in animal pain models, however, have led to skepticism around the potential of selective NaV1.7 inhibitors as human therapeutics. In this Perspective, we discuss the attributes and limitations of recently disclosed investigational drugs targeting NaV1.7 and review evidence that, by better understanding the requirements for selectivity and target engagement, the opportunity to deliver effective analgesic medicines targeting NaV1.7 endures.


Asunto(s)
Analgésicos/química , Canal de Sodio Activado por Voltaje NAV1.7/metabolismo , Bloqueadores de los Canales de Sodio/química , Analgésicos/metabolismo , Analgésicos/farmacología , Analgésicos/uso terapéutico , Animales , Modelos Animales de Enfermedad , Humanos , Canal de Sodio Activado por Voltaje NAV1.7/química , Dolor/tratamiento farmacológico , Dolor/patología , Isoformas de Proteínas/antagonistas & inhibidores , Isoformas de Proteínas/metabolismo , Transducción de Señal/efectos de los fármacos , Bloqueadores de los Canales de Sodio/metabolismo , Bloqueadores de los Canales de Sodio/farmacología , Bloqueadores de los Canales de Sodio/uso terapéutico , Sulfonamidas/química , Sulfonamidas/metabolismo
8.
J Neurosci ; 36(3): 701-13, 2016 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-26791202

RESUMEN

Early binge-like alcohol drinking may promote the development of hazardous intake. However, the enduring cellular alterations following the first experience with alcohol consumption are not fully understood. We found that the first binge-drinking alcohol session produced enduring enhancement of excitatory synaptic transmission onto dopamine D1 receptor-expressing neurons (D1+ neurons) in the nucleus accumbens (NAc) shell but not the core in mice, which required D1 receptors (D1Rs) and mechanistic target of rapamycin complex 1 (mTORC1). Furthermore, inhibition of mTORC1 activity during the first alcohol drinking session reduced alcohol consumption and preference of a subsequent drinking session. mTORC1 is critically involved in RNA-to-protein translation, and we found that the first alcohol session rapidly activated mTORC1 in NAc shell D1+ neurons and increased synaptic expression of the AMPAR subunit GluA1 and the scaffolding protein Homer. Finally, D1R stimulation alone was sufficient to activate mTORC1 in the NAc to promote mTORC1-dependent translation of the synaptic proteins GluA1 and Homer. Together, our results indicate that the first alcohol drinking session induces synaptic plasticity in NAc D1+ neurons via enhanced mTORC1-dependent translation of proteins involved in excitatory synaptic transmission that in turn drives the reinforcement learning associated with the first alcohol experience. Thus, the alcohol-dependent D1R/mTORC1-mediated increase in synaptic function in the NAc may reflect a neural imprint of alcohol's reinforcing properties, which could promote subsequent alcohol intake. Significance statement: Consuming alcohol for the first time is a learning event that drives further drinking. Here, we identified a mechanism that may underlie the reinforcing learning associated with the initial alcohol experience. We show that the first alcohol experience induces a persistent enhancement of excitatory synaptic transmission on NAc shell D1+ neurons, which is dependent on D1R and mTORC1. We also find that mTORC1 is necessary for the sustained alcohol consumption and preference across the initial drinking sessions. The first alcohol binge activates mTORC1 in NAc D1+ neurons and increases levels of synaptic proteins involved in glutamatergic signaling. Thus, the D1R/mTORC1-dependent plasticity following the first alcohol exposure may be a critical cellular component of reinforcement learning.


Asunto(s)
Consumo de Bebidas Alcohólicas/metabolismo , Complejos Multiproteicos/biosíntesis , Plasticidad Neuronal/fisiología , Neuronas/metabolismo , Núcleo Accumbens/metabolismo , Receptores de Dopamina D1/biosíntesis , Serina-Treonina Quinasas TOR/biosíntesis , Animales , Consumo Excesivo de Bebidas Alcohólicas/metabolismo , Etanol/administración & dosificación , Masculino , Diana Mecanicista del Complejo 1 de la Rapamicina , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Plasticidad Neuronal/efectos de los fármacos , Neuronas/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Técnicas de Cultivo de Órganos , Refuerzo en Psicología
9.
Addict Biol ; 21(3): 530-46, 2016 May.
Artículo en Inglés | MEDLINE | ID: mdl-25752326

RESUMEN

Abused inhalants are voluntarily inhaled at high concentrations to produce intoxicating effects. Results from animal studies show that the abused inhalant toluene triggers behaviors, such as self-administration and conditioned place preference, which are commonly associated with addictive drugs. However, little is known about how toluene affects neurons within the nucleus accumbens (NAc), a brain region within the basal ganglia that mediates goal-directed behaviors and is implicated in the development and maintenance of addictive behaviors. Here we report that toluene inhibits a component of the after-hyperpolarization potential, and dose-dependently inhibits N-methyl-D-aspartate (NMDA)-mediated currents in rat NAc medium spiny neurons (MSN). Moreover, using the multivariate statistical technique, partial least squares discriminative analysis to analyze electrophysiological measures from rat NAc MSNs, we show that toluene induces a persistent depression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-mediated currents in one subtype of NAc MSNs, and that the electrophysiological features of MSN neurons predicts their sensitivity to toluene. The CB1 receptor antagonist AM281 blocked the toluene-induced long-term depression of AMPA currents, indicating that this process is dependent on endocannabinoid signaling. The neuronal identity of recorded cells was examined using dual histochemistry and shows that toluene-sensitive NAc neurons are dopamine D2 MSNs that express preproenkephalin mRNA. Overall, the results from these studies indicate that physiological characteristics obtained from NAc MSNs during whole-cell patch-clamp recordings reliably predict neuronal phenotype, and that the abused inhalant toluene differentially depresses excitatory neurotransmission in NAc neuronal subtypes.


Asunto(s)
Abuso de Inhalantes , Depresión Sináptica a Largo Plazo/efectos de los fármacos , Inhibición Neural/efectos de los fármacos , Neuronas/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Solventes/farmacología , Transmisión Sináptica/efectos de los fármacos , Tolueno/farmacología , Animales , Encefalinas/genética , Ácido Glutámico/metabolismo , Inmunohistoquímica , Morfolinas/farmacología , N-Metilaspartato , Neuronas/metabolismo , Núcleo Accumbens/metabolismo , Fenotipo , Precursores de Proteínas/genética , Pirazoles/farmacología , ARN Mensajero/metabolismo , Ratas , Receptor Cannabinoide CB1/antagonistas & inhibidores , Receptores de Dopamina D2/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/metabolismo
10.
Nat Neurosci ; 17(4): 577-85, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-24584054

RESUMEN

The ventral pallidum is centrally positioned within mesocorticolimbic reward circuits, and its dense projection to the ventral tegmental area (VTA) regulates neuronal activity there. However, the ventral pallidum is a heterogeneous structure, and how this complexity affects its role within wider reward circuits is unclear. We found that projections to VTA from the rostral ventral pallidum (RVP), but not the caudal ventral pallidum (CVP), were robustly Fos activated during cue-induced reinstatement of cocaine seeking--a rat model of relapse in addiction. Moreover, designer receptor-mediated transient inactivation of RVP neurons, their terminals in VTA or functional connectivity between RVP and VTA dopamine neurons blocked the ability of drug-associated cues (but not a cocaine prime) to reinstate cocaine seeking. In contrast, CVP neuronal inhibition blocked cocaine-primed, but not cue-induced, reinstatement. This double dissociation in ventral pallidum subregional roles in drug seeking is likely to be important for understanding the mesocorticolimbic circuits underlying reward seeking and addiction.


Asunto(s)
Ganglios Basales/metabolismo , Trastornos Relacionados con Cocaína/metabolismo , Cocaína/farmacología , Neuronas Dopaminérgicas/metabolismo , Vías Nerviosas/metabolismo , Receptores Dopaminérgicos/metabolismo , Área Tegmental Ventral/metabolismo , Animales , Ganglios Basales/efectos de los fármacos , Ganglios Basales/patología , Conducta Animal/efectos de los fármacos , Cocaína/administración & dosificación , Señales (Psicología) , Modelos Animales de Enfermedad , Neuronas Dopaminérgicas/efectos de los fármacos , Neuronas Dopaminérgicas/fisiología , Masculino , Inhibición Neural/efectos de los fármacos , Vías Nerviosas/efectos de los fármacos , Ratas , Ratas Long-Evans , Ratas Sprague-Dawley , Receptores Dopaminérgicos/efectos de los fármacos , Recurrencia , Recompensa , Área Tegmental Ventral/efectos de los fármacos , Área Tegmental Ventral/patología
11.
PLoS One ; 8(11): e80541, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24244696

RESUMEN

Ethanol's action on the brain likely reflects altered function of key ion channels such as glutamatergic N-methyl-D-aspartate receptors (NMDARs). In this study, we determined how expression of a mutant GluN1 subunit (F639A) that reduces ethanol inhibition of NMDARs affects ethanol-induced behaviors in mice. Mice homozygous for the F639A allele died prematurely while heterozygous knock-in mice grew and bred normally. Ethanol (44 mM; ∼0.2 g/dl) significantly inhibited NMDA-mediated EPSCs in wild-type mice but had little effect on responses in knock-in mice. Knock-in mice had normal expression of GluN1 and GluN2B protein across different brain regions and a small reduction in levels of GluN2A in medial prefrontal cortex. Ethanol (0.75-2.0 g/kg; i.p.) increased locomotor activity in wild-type mice but had no effect on knock-in mice while MK-801 enhanced activity to the same extent in both groups. Ethanol (2.0 g/kg) reduced rotarod performance equally in both groups but knock-in mice recovered faster following a higher dose (2.5 g/kg). In the elevated zero maze, knock-in mice had a blunted anxiolytic response to ethanol (1.25 g/kg) as compared to wild-type animals. No differences were noted between wild-type and knock-in mice for ethanol-induced loss of righting reflex, sleep time, hypothermia or ethanol metabolism. Knock-in mice consumed less ethanol than wild-type mice during daily limited-access sessions but drank more in an intermittent 24 h access paradigm with no change in taste reactivity or conditioned taste aversion. Overall, these data support the hypothesis that NMDA receptors are important in regulating a specific constellation of effects following exposure to ethanol.


Asunto(s)
Etanol/farmacología , Actividad Motora/efectos de los fármacos , Actividad Motora/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Western Blotting , Línea Celular , Electrofisiología , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Receptores de N-Metil-D-Aspartato/genética
12.
Neuropsychopharmacology ; 38(13): 2555-67, 2013 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-23954847

RESUMEN

Volatile solvents such as those found in fuels, paints, and thinners are found throughout the world and are used in a variety of industrial applications. However, these compounds are also often intentionally inhaled at high concentrations to produce intoxication. While solvent use has been recognized as a potential drug problem for many years, research on the sites and mechanisms of action of these compounds lags behind that of other drugs of abuse. In this review, we first discuss the epidemiology of voluntary solvent use throughout the world and then consider what is known about their basic pharmacology and how this may explain their use as drugs of abuse. We next present data from preclinical and clinical studies indicating that these substances induce common addiction sequelae such as dependence, withdrawal, and cognitive impairments. We describe how toluene, the most commonly studied psychoactive volatile solvent, alters synaptic transmission in key brain circuits such as the mesolimbic dopamine system and medial prefrontal cortex (mPFC) that are thought to underlie addiction pathology. Finally, we make the case that activity in mPFC circuits is a critical regulator of the mesolimbic dopamine system's ability to respond to volatile solvents like toluene. Overall, this review provides evidence that volatile solvents have high abuse liability because of their selective effects on critical nodes of the addiction neurocircuitry, and underscores the need for more research into how these compounds induce adaptations in neural circuits that underlie addiction pathology.


Asunto(s)
Corteza Cerebral/patología , Sistema Límbico/patología , Solventes/efectos adversos , Trastornos Relacionados con Sustancias/etiología , Trastornos Relacionados con Sustancias/patología , Animales , Humanos
13.
J Neurosci ; 33(2): 804-13, 2013 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-23303956

RESUMEN

Toluene is a volatile solvent that is intentionally inhaled by children, adolescents, and adults for its intoxicating effects. Although voluntary use of toluene suggests that it possesses rewarding properties and abuse potential, it is unknown whether toluene alters excitatory synaptic transmission in reward-sensitive dopamine neurons like other drugs of abuse. Here, using a combination of retrograde labeling and slice electrophysiology, we show that a brief in vivo exposure of rats to a behaviorally relevant concentration of toluene vapor enhances glutamatergic synaptic strength of dopamine (DA) neurons projecting to nucleus accumbens core and medial shell neurons. This effect persisted for up to 3 d in mesoaccumbens core DA neurons and for at least 21 d in those projecting to the medial shell. In contrast, toluene vapor exposure had no effect on synaptic strength of DA neurons that project to the medial prefrontal cortex (mPFC). Furthermore, infusion of GABAergic modulators into the mPFC before vapor exposure to pharmacologically manipulate output, inhibited, or potentiated toluene's action on mesoaccumbens DA neurons. Together, the results of these studies indicate that toluene induces a target-selective increase in mesolimbic DA neuron synaptic transmission and strongly implicates the mPFC as an important regulator of drug-induced plasticity of mesolimbic dopamine neurons.


Asunto(s)
Neuronas Dopaminérgicas/fisiología , Sistema Límbico/fisiología , Plasticidad Neuronal/fisiología , Corteza Prefrontal/fisiología , Sinapsis/fisiología , Tolueno/farmacología , Animales , Biomarcadores , Interpretación Estadística de Datos , Neuronas Dopaminérgicas/efectos de los fármacos , Estimulación Eléctrica , Fenómenos Electrofisiológicos , Sistema Límbico/citología , Sistema Límbico/efectos de los fármacos , Masculino , Microinyecciones , Plasticidad Neuronal/efectos de los fármacos , Corteza Prefrontal/citología , Corteza Prefrontal/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Estándares de Referencia , Técnicas Estereotáxicas , Sinapsis/efectos de los fármacos , Tirosina 3-Monooxigenasa/metabolismo , Área Tegmental Ventral/citología , Área Tegmental Ventral/efectos de los fármacos , Área Tegmental Ventral/fisiología
14.
Neuropsychopharmacology ; 38(7): 1176-88, 2013 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-23314219

RESUMEN

Trauma-induced damage to the orbitofrontal cortex (OFC) often results in behavioral inflexibility and impaired judgment. Human alcoholics exhibit similar cognitive deficits suggesting that OFC neurons are susceptible to alcohol-induced dysfunction. A previous study from this laboratory examined OFC mediated cognitive behaviors in mice and showed that behavioral flexibility during a reversal learning discrimination task was reduced in alcohol-dependent mice. Despite these intriguing findings, the actions of alcohol on OFC neuron function are unknown. To address this issue, slices containing the lateral OFC (lOFC) were prepared from adult C57BL/6J mice and whole-cell patch clamp electrophysiology was used to characterize the effects of ethanol (EtOH) on neuronal function. EtOH (66 mM) had no effect on AMPA-mediated EPSCs but decreased those mediated by NMDA receptors. EtOH (11-66 mM) also decreased current-evoked spike firing and this was accompanied by a decrease in input resistance and a modest hyperpolarization. EtOH inhibition of spike firing was prevented by the GABAA antagonist picrotoxin, but EtOH had no effect on evoked or spontaneous GABA IPSCs. EtOH increased the holding current of voltage-clamped neurons and this action was blocked by picrotoxin but not the more selective GABAA antagonist biccuculine. The glycine receptor antagonist strychnine also prevented EtOH's effect on holding current and spike firing, and western blotting revealed the presence of glycine receptors in lOFC. Overall, these results suggest that acutely, EtOH may reduce lOFC function via a glycine receptor dependent process and this may trigger neuroadaptive mechanisms that contribute to the impairment of OFC-dependent behaviors in alcohol-dependent subjects.


Asunto(s)
Etanol/farmacología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Corteza Prefrontal/citología , Corteza Prefrontal/efectos de los fármacos , Receptores de Glicina/metabolismo , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Bicuculina/farmacología , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Etanol/antagonistas & inhibidores , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Potenciales Postsinápticos Excitadores/fisiología , Antagonistas del GABA/farmacología , Glicinérgicos/farmacología , Técnicas In Vitro , Masculino , Ratones , Picrotoxina/farmacología , Corteza Prefrontal/fisiología , Receptores AMPA/efectos de los fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Estricnina/farmacología
15.
Neuropsychopharmacology ; 36(7): 1531-42, 2011 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-21430649

RESUMEN

Volatile organic solvents such as toluene are voluntarily inhaled for their intoxicating effects. Solvent use is especially prevalent among adolescents, and is associated with deficits in a wide range of cognitive tasks including attention, behavioral control, and risk assessment. Despite these findings, little is known about the effects of toluene on brain areas mediating these behaviors. In this study, whole-cell patch-clamp recordings were used to determine the effect toluene on neurons within the medial PFC, a region critically involved in cognitive function. Toluene had no effect on measures of intrinsic excitability, but enhanced stimulus-evoked γ-amino butyric acid A-mediated inhibitory postsynaptic currents (IPSCs). In the presence of tetrodotoxin (TTX) to block action potentials, toluene increased the frequency and amplitude of miniature IPSCs. In contrast, toluene induced a delayed but persistent decrease in evoked or spontaneous AMPA-mediated excitatory postsynaptic currents (EPSCs). This effect was prevented by an intracellular calcium chelator or by the ryanodine receptor and SERCA inhibitors, dantrolene or thapsigargin, respectively, suggesting that toluene may mobilize intracellular calcium pools. The toluene-induced reduction in AMPA EPSCs was also prevented by a cannabinoid receptor (CB1R) antagonist, and was occluded by the CB1 agonist WIN 55,212-2 that itself induced a profound decrease in AMPA-mediated EPSCs. Toluene had no effect on the frequency or amplitude of miniature EPSCs recorded in the presence of TTX. Finally, toluene dose-dependently inhibited N-methyl-D-aspartate (NMDA)-mediated EPSCs and the magnitude and reversibility of this effect was CB1R sensitive indicating both direct and indirect actions of toluene on NMDA-mediated responses. Together, these results suggest that the effect of toluene on cognitive behaviors may result from its action on inhibitory and excitatory synaptic transmission of PFC neurons.


Asunto(s)
Neuronas/efectos de los fármacos , Corteza Prefrontal/citología , Solventes/farmacología , Transmisión Sináptica/efectos de los fármacos , Tolueno/farmacología , Potenciales de Acción/efectos de los fármacos , Análisis de Varianza , Animales , Animales Recién Nacidos , Benzoxazinas/farmacología , Biofisica , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Estimulación Eléctrica , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Técnicas In Vitro , Potenciales Postsinápticos Inhibidores/efectos de los fármacos , Masculino , Morfolinas/farmacología , Naftalenos/farmacología , Inhibición Neural/efectos de los fármacos , Técnicas de Placa-Clamp , Corteza Prefrontal/efectos de los fármacos , Probabilidad , Pirazoles/farmacología , Ratas , Ratas Sprague-Dawley , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/farmacología , Ácido gamma-Aminobutírico/farmacología
16.
Neurosci Lett ; 474(1): 52-7, 2010 Apr 19.
Artículo en Inglés | MEDLINE | ID: mdl-20223277

RESUMEN

Neonatal bacterial infection in rats alters the responses to a variety of subsequent challenges later in life. Here we explored the effects of neonatal bacterial infection on a subsequent drug challenge during adolescence, using administration of the psychostimulant amphetamine. Male rat pups were injected on postnatal day 4 (P4) with live Escherichia coli (E. coli) or PBS vehicle, and then received amphetamine (15mg/kg) or saline on P40. Quantitative RT-PCR was performed on micropunches taken from medial prefrontal cortex, nucleus accumbens, and the CA1 subfield of the hippocampus. mRNA for glial and neuronal activation markers as well as pro-inflammatory and anti-inflammatory cytokines were assessed. Amphetamine produced brain region specific increases in many of these genes in PBS controls, while these effects were blunted or absent in neonatal E. coli treated rats. In contrast to the potentiating effect of neonatal E. coli on glial and cytokine responses to an immune challenge previously observed, neonatal E. coli infection attenuates glial and cytokine responses to an amphetamine challenge.


Asunto(s)
Anfetamina/farmacología , Estimulantes del Sistema Nervioso Central/farmacología , Citocinas/biosíntesis , Infecciones por Escherichia coli/inmunología , Infecciones por Escherichia coli/metabolismo , Proteínas de la Membrana/biosíntesis , Neuroglía/efectos de los fármacos , Neuronas/efectos de los fármacos , Factores de Edad , Animales , Animales Recién Nacidos , Antígenos CD/biosíntesis , Antígenos CD/genética , Antígeno CD11b/biosíntesis , Antígeno CD11b/genética , Citocinas/genética , Proteínas del Citoesqueleto/biosíntesis , Proteínas del Citoesqueleto/genética , Infecciones por Escherichia coli/complicaciones , Expresión Génica , Proteína Ácida Fibrilar de la Glía/biosíntesis , Proteína Ácida Fibrilar de la Glía/genética , Masculino , Proteínas de la Membrana/genética , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/genética , Neuroglía/metabolismo , Neuronas/metabolismo , ARN Mensajero/biosíntesis , Ratas
17.
Brain Behav Immun ; 24(3): 329-38, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-19782746

RESUMEN

Systemic infection with Escherichia coli on postnatal day (P) 4 in rats results in significantly altered brain cytokine responses and behavioral changes in adulthood, but only in response to a subsequent immune challenge with lipopolysaccharide [LPS]. The basis for these changes may be long-term changes in glial cell function. We assessed glial and neural cell genesis in the hippocampus, parietal cortex (PAR), and prefrontal cortex (PFC), in neonates just after the infection, as well as in adulthood in response to LPS. E. coli increased the number of newborn microglia within the hippocampus and PAR compared to controls. The total number of microglia was also significantly increased in E. coli-treated pups, with a concomitant decrease in total proliferation. On P33, there were large decreases in numbers of cells coexpressing BrdU and NeuN in all brain regions of E. coli rats compared to controls. In adulthood, basal neurogenesis within the dentate gyrus (DG) did not differ between groups; however, in response to LPS, there was a decrease in neurogenesis in early-infected rats, but an increase in controls to the same challenge. There were also significantly more microglia in the adult DG of early-infected rats, although microglial proliferation in response to LPS was increased in controls. Taken together, we have provided evidence that systemic infection with E. coli early in life has significant, enduring consequences for brain development and subsequent adult function. These changes include marked alterations in glia, as well as influences on neurogenesis in brain regions important for cognition.


Asunto(s)
Encéfalo/patología , Encéfalo/fisiología , Infecciones del Sistema Nervioso Central/patología , Infecciones del Sistema Nervioso Central/psicología , Cognición/fisiología , Infecciones por Escherichia coli/patología , Infecciones por Escherichia coli/psicología , Neuroglía/patología , Neuronas/patología , Animales , Animales Recién Nacidos , Antimetabolitos , Bromodesoxiuridina , Recuento de Células , Proliferación Celular , Supervivencia Celular , Femenino , Inmunohistoquímica , Lipopolisacáridos/farmacología , Masculino , Neuroglía/fisiología , Neuronas/fisiología , Fenotipo , Ratas , Ratas Sprague-Dawley
18.
Neuropsychopharmacology ; 34(4): 834-43, 2009 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-18368036

RESUMEN

Experiential factors, such as stress, are major determinants of vulnerability to drug addiction and relapse. The behavioral controllability of the stressor is a major determinant of how exposure to a stressor impacts addictive processes. Recent evidence suggests that controllable stressors, such as escapable shock (ES), activate ventral regions of the medial prefrontal cortex (mPFCv), whereas physically identical, but uncontrollable stress (inescapable shock, IS) does not. This activation is critical to the blunting effect that control has on neurochemical and behavioral sequelae of stress. Our laboratory has previously shown that IS, but not ES, potentiates morphine-conditioned place preference (CPP). However, the role of the mPFCv in this phenomenon is unknown. The present experiments investigated the role of the mPFCv during ES and IS in determining the effects of the stressor on subsequent morphine-CPP. Intra-mPFCv microinjection of the GABA(A) agonist muscimol 1 h before ES led ES to potentiate morphine-CPP, as does IS. Conversely, the potentiation of morphine-CPP normally observed in IS rats was blocked by intra-mPFCv microinjection of the GABA(A) antagonist picrotoxin 1 h before IS. These results suggest that during stress, activation of the mPFCv prevents subsequent potentiation of morphine-CPP, whereas inactivation of the mPFCv during stress does not. Thus, activation of the mPFCv during a stress experience is both necessary and sufficient to block the impact of stress on morphine-CPP, and control over stress blunts stress-induced potentiation of morphine effects by activating the mPFCv.


Asunto(s)
Conducta Animal , Condicionamiento Psicológico , Morfina/farmacología , Corteza Prefrontal/fisiología , Estrés Psicológico/fisiopatología , Análisis de Varianza , Animales , Conducta Animal/efectos de los fármacos , Reacción de Fuga/efectos de los fármacos , Agonistas del GABA/farmacología , Antagonistas del GABA/farmacología , Agonistas de Receptores de GABA-A , Antagonistas de Receptores de GABA-A , Masculino , Microinyecciones , Actividad Motora/efectos de los fármacos , Muscimol/farmacología , Picrotoxina/farmacología , Ratas , Ratas Sprague-Dawley
19.
Behav Brain Res ; 181(1): 127-35, 2007 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-17499370

RESUMEN

Diverse cholinergic signaling mechanisms regulate the excitability of striatal principal neurons and modulate striatal-dependent behavior. These effects are mediated, in part, by action at muscarinic receptors (mAChR), subtypes of which exhibit distinct patterns of expression across striatal neuronal populations. Non-selective mAChR blockade within the nucleus accumbens (NAc) has been shown to disrupt operant responding for food and to inhibit food consumption. However, the specific receptor subtypes mediating these effects are not known. Thus, we evaluated effects of intra-NAc infusions of pirenzepine and methoctramine, mAChR antagonisits with distinct binding affinity profiles, on operant responding for sucrose reward under a progressive ratio (PR) reinforcement schedule. Moderate to high doses of methoctramine disrupted operant responding and reduced behavioral breakpoint. In contrast, pirenzepine failed to impact operant performance at any dose tested. Methoctramine failed to affect latencies to complete appetitive-consummatory response sequences or to impact measures of acoustic startle, suggesting that its' disruptive effects on operant behavior were not consequent to gross motor impairment. Since methoctramine has a greater affinity for M(2) receptors compared to pirenzepine, which has a greater relative affinity for M(1) and M(3) receptors, these findings suggest that M(2) mAChRs within the NAc regulate behavioral processes underling the acquisition of reward.


Asunto(s)
Condicionamiento Operante/efectos de los fármacos , Diaminas/farmacología , Antagonistas Muscarínicos/farmacología , Núcleo Accumbens/efectos de los fármacos , Pirenzepina/farmacología , Sacarosa , Estimulación Acústica/métodos , Animales , Conducta Animal , Relación Dosis-Respuesta a Droga , Conducta Exploratoria/efectos de los fármacos , Preferencias Alimentarias/efectos de los fármacos , Inhibición Psicológica , Masculino , Ratas , Ratas Sprague-Dawley , Reflejo Acústico/efectos de los fármacos , Esquema de Refuerzo
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