RESUMEN

Food and water are rewarding in part because they satisfy our internal needs1,2. Dopaminergic neurons in the ventral tegmental area (VTA) are activated by gustatory rewards3-5, but how animals learn to associate these oral cues with the delayed physiological effects of ingestion is unknown. Here we show that individual dopaminergic neurons in the VTA respond to detection of nutrients or water at specific stages of ingestion. A major subset of dopaminergic neurons tracks changes in systemic hydration that occur tens of minutes after thirsty mice drink water, whereas different dopaminergic neurons respond to nutrients in the gastrointestinal tract. We show that information about fluid balance is transmitted to the VTA by a hypothalamic pathway and then re-routed to downstream circuits that track the oral, gastrointestinal and post-absorptive stages of ingestion. To investigate the function of these signals, we used a paradigm in which a fluid's oral and post-absorptive effects can be independently manipulated and temporally separated. We show that mice rapidly learn to prefer one fluid over another based solely on its rehydrating ability and that this post-ingestive learning is prevented if dopaminergic neurons in the VTA are selectively silenced after consumption. These findings reveal that the midbrain dopamine system contains subsystems that track different modalities and stages of ingestion, on timescales from seconds to tens of minutes, and that this information is used to drive learning about the consequences of ingestion.

Asunto(s)

Dopamina , Neuronas Dopaminérgicas , Hipotálamo , Vías Nerviosas , Nutrientes , Estado de Hidratación del Organismo , Área Tegmental Ventral , Animales , Señales (Psicología) , Digestión , Dopamina/metabolismo , Neuronas Dopaminérgicas/fisiología , Ingestión de Alimentos , Tracto Gastrointestinal/metabolismo , Hipotálamo/citología , Hipotálamo/fisiología , Mesencéfalo/citología , Mesencéfalo/fisiología , Ratones , Nutrientes/metabolismo , Estado de Hidratación del Organismo/efectos de los fármacos , Recompensa , Factores de Tiempo , Área Tegmental Ventral/citología , Área Tegmental Ventral/fisiología , Agua/metabolismo , Agua/farmacología , Equilibrio Hidroelectrolítico

RESUMEN

Abnormal involuntary movements, or dyskinesias, are seen in many neurologic diseases, including disorders where the brain appears grossly normal. This observation suggests that alterations in neural activity or connectivity may underlie dyskinesias. One influential model proposes that involuntary movements are driven by an imbalance in the activity of striatal direct and indirect pathway neurons (dMSNs and iMSNs, respectively). Indeed, in some animal models, there is evidence that dMSN hyperactivity contributes to dyskinesia. Given the many diseases associated with dyskinesia, it is unclear whether these findings generalize to all forms. Here, we used male and female mice in a mouse model of paroxysmal nonkinesigenic dyskinesia (PNKD) to assess whether involuntary movements are related to aberrant activity in the striatal direct and indirect pathways. In this model, as in the human disorder PNKD, animals experience dyskinetic attacks in response to caffeine or alcohol. Using optically identified striatal single-unit recordings in freely moving PNKD mice, we found a loss of iMSN firing during dyskinesia bouts. Further, chemogenetic inhibition of iMSNs triggered dyskinetic episodes in PNKD mice. Finally, we found that these decreases in iMSN firing are likely because of aberrant endocannabinoid-mediated suppression of glutamatergic inputs. These data show that striatal iMSN dysfunction contributes to the etiology of dyskinesia in PNKD, and suggest that indirect pathway hypoactivity may be a key mechanism for the generation of involuntary movements in other disorders.SIGNIFICANCE STATEMENT Involuntary movements, or dyskinesias, are part of many inherited and acquired neurologic syndromes. There are few effective treatments, most of which have significant side effects. Better understanding of which cells and patterns of activity cause dyskinetic movements might inform the development of new neuromodulatory treatments. In this study, we used a mouse model of an inherited human form of paroxysmal dyskinesia in combination with cell type-specific tools to monitor and manipulate striatal activity. We were able to narrow in on a specific group of neurons that causes dyskinesia in this model, and found alterations in a well-known form of plasticity in this cell type, endocannabinoid-dependent synaptic LTD. These findings point to new areas for therapeutic development.

Asunto(s)

Corea , Discinesias , Animales , Corea/inducido químicamente , Cuerpo Estriado , Modelos Animales de Enfermedad , Discinesias/etiología , Femenino , Levodopa/efectos adversos , Masculino , Ratones , Neuronas

RESUMEN

The dorsomedial prefrontal cortex (dmPFC) has been linked to avoidance and decision-making under conflict, key neural computations altered in anxiety disorders. However, the heterogeneity of prefrontal projections has obscured identification of specific top-down projections involved. While the dmPFC-amygdala circuit has long been implicated in controlling reflexive fear responses, recent work suggests that dmPFC-dorsomedial striatum (DMS) projections may be more important for regulating avoidance. Using fiber photometry recordings in both male and female mice during the elevated zero maze task, we show heightened neural activity in frontostriatal but not frontoamygdalar projection neurons during exploration of the anxiogenic open arms. Additionally, using optogenetics, we demonstrate that this frontostriatal projection preferentially excites postsynaptic D1 receptor-expressing neurons in the DMS and causally controls innate avoidance behavior. These results support a model for prefrontal control of defensive behavior in which the dmPFC-amygdala projection controls reflexive fear behavior and the dmPFC-striatum projection controls anxious avoidance behavior.SIGNIFICANCE STATEMENT The medial prefrontal cortex has been extensively linked to several behavioral symptom domains related to anxiety disorders, with much of the work centered around reflexive fear responses. Comparatively little is known at the mechanistic level about anxious avoidance behavior, a core feature across anxiety disorders. Recent work has suggested that the striatum may be an important hub for regulating avoidance behaviors. Our work uses optical circuit dissection techniques to identify a specific corticostriatal circuit involved in encoding and controlling avoidance behavior. Identifying neural circuits for avoidance will enable the development of more targeted symptom-specific treatments for anxiety disorders.

Asunto(s)

Reacción de Prevención/fisiología , Cuerpo Estriado/fisiología , Vías Nerviosas/fisiología , Corteza Prefrontal/fisiología , Animales , Conducta Animal/fisiología , Femenino , Instinto , Masculino , Ratones , Ratones Endogámicos C57BL

RESUMEN

A key assumption of optogenetics is that light only affects opsin-expressing neurons. However, illumination invariably heats tissue, and many physiological processes are temperature-sensitive. Commonly used illumination protocols increased the temperature by 0.2-2 °C and suppressed spiking in multiple brain regions. In the striatum, light delivery activated an inwardly rectifying potassium conductance and biased rotational behavior. Thus, careful consideration of light-delivery parameters is required, as even modest intracranial heating can confound interpretation of optogenetic experiments.

Asunto(s)

Corteza Cerebral/fisiología , Cuerpo Estriado/fisiología , Hipocampo/fisiología , Neuronas/fisiología , Temperatura , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/efectos de la radiación , Animales , Compuestos de Bario/farmacología , Corteza Cerebral/citología , Cloruros/farmacología , Cuerpo Estriado/citología , Hipocampo/citología , Calor , Transporte Iónico/efectos de los fármacos , Transporte Iónico/efectos de la radiación , Luz , Ratones , Actividad Motora/efectos de la radiación , Neuronas/efectos de los fármacos , Neuronas/efectos de la radiación , Optogenética/métodos , Técnicas de Placa-Clamp , Potasio/metabolismo , Canales de Potasio de Rectificación Interna/efectos de los fármacos , Canales de Potasio de Rectificación Interna/metabolismo , Canales de Potasio de Rectificación Interna/efectos de la radiación , Proyectos de Investigación

RESUMEN

BACKGROUND: Intracranial photometry through chronically implanted optical fibers is a widely adopted technique for measuring signals from fluorescent probes in deep-brain structures. The recent proliferation of bright, photo-stable, and specific genetically encoded fluorescent reporters for calcium and for other neuromodulators has greatly increased the utility and popularity of this technique. NEW METHOD: Here we describe an open-source, cost-effective, microcontroller-based solution for controlling optical components in an intracranial photometry system and processing the resulting signal. RESULTS: We show proof-of-principle that this system supports high quality intracranial photometry recordings from dorsal striatum in freely moving mice. A single system supports simultaneous fluorescence measurements in two independent color channels, but multiple systems can be integrated together if additional fluorescence channels are required. This system is designed to work in combination with either commercially available or custom-built optical components. Parts can be purchased for less than one tenth the cost of commercially available alternatives and complete assembly takes less than one day for an inexperienced user. COMPARISON WITH EXISTING METHOD(S): Currently available hardware draws on a variety of commercial, custom-built, or hybrid elements for both optical and electronic components. Many of these hardware systems are either specialized and inflexible, or over-engineered and expensive. CONCLUSIONS: This open-source system increases experimental flexibility while reducing cost relative to current commercially available components. All software and firmware are open-source and customizable, affording a degree of experimental flexibility that is not available in current commercial systems.

Asunto(s)

Cuerpo Estriado/diagnóstico por imagen , Fluorometría/instrumentación , Fluorometría/métodos , Imagen Óptica/instrumentación , Imagen Óptica/métodos , Animales , Señalización del Calcio , Cuerpo Estriado/metabolismo , Diseño de Equipo , Ratones , Fibras Ópticas , Programas Informáticos

RESUMEN

Reinforcement has long been thought to require striatal synaptic plasticity. Indeed, direct striatal manipulations such as self-stimulation of direct-pathway projection neurons (dMSNs) are sufficient to induce reinforcement within minutes. However, it's unclear what role, if any, is played by downstream circuitry. Here, we used dMSN self-stimulation in mice as a model for striatum-driven reinforcement and mapped the underlying circuitry across multiple basal ganglia nuclei and output targets. We found that mimicking the effects of dMSN activation on downstream circuitry, through optogenetic suppression of basal ganglia output nucleus substantia nigra reticulata (SNr) or activation of SNr targets in the brainstem or thalamus, was also sufficient to drive rapid reinforcement. Remarkably, silencing motor thalamus-but not other selected targets of SNr-was the only manipulation that reduced dMSN-driven reinforcement. Together, these results point to an unexpected role for basal ganglia output to motor thalamus in striatum-driven reinforcement.

Asunto(s)

Actividad Motora/fisiología , Neostriado/fisiología , Refuerzo en Psicología , Tálamo/fisiología , Animales , Ganglios Basales/fisiología , Estimulación Eléctrica , Femenino , Glutamatos/metabolismo , Masculino , Ratones , Optogenética , Receptores de N-Metil-D-Aspartato/metabolismo , Neuronas Serotoninérgicas/metabolismo , Transmisión Sináptica/fisiología

RESUMEN

Single-cell RNA sequencing provides a new approach to an old problem: how to study cellular diversity in complex biological systems. Three studies-Saunders et al., Zeisel et al., and Davie et al.-deploy this technique on an unprecedented scale to reveal transcriptional patterns that distinguish cells in the nervous systems of mice and flies.

Asunto(s)

Drosophila , Transcriptoma , Animales , Secuencia de Bases , Encéfalo , Ratones , Análisis de Secuencia de ARN

RESUMEN

Dopamine (DA) is a central monoamine neurotransmitter involved in many physiological and pathological processes. A longstanding yet largely unmet goal is to measure DA changes reliably and specifically with high spatiotemporal precision, particularly in animals executing complex behaviors. Here, we report the development of genetically encoded GPCR-activation-based-DA (GRABDA) sensors that enable these measurements. In response to extracellular DA, GRABDA sensors exhibit large fluorescence increases (ΔF/F0 ∼90%) with subcellular resolution, subsecond kinetics, nanomolar to submicromolar affinities, and excellent molecular specificity. GRABDA sensors can resolve a single-electrical-stimulus-evoked DA release in mouse brain slices and detect endogenous DA release in living flies, fish, and mice. In freely behaving mice, GRABDA sensors readily report optogenetically elicited nigrostriatal DA release and depict dynamic mesoaccumbens DA signaling during Pavlovian conditioning or during sexual behaviors. Thus, GRABDA sensors enable spatiotemporally precise measurements of DA dynamics in a variety of model organisms while exhibiting complex behaviors.

Asunto(s)

Dopamina/análisis , Drosophila/metabolismo , Pez Cebra/metabolismo , Animales , Animales Modificados Genéticamente/genética , Animales Modificados Genéticamente/metabolismo , Conducta Animal , Dopamina/metabolismo , Femenino , Proteínas Fluorescentes Verdes/genética , Células HEK293 , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Microscopía Fluorescente , Neuronas/citología , Neuronas/metabolismo , Optogenética/métodos , Receptores Acoplados a Proteínas G/genética , Canales Catiónicos TRPV/genética , Proteínas de Pez Cebra/genética

Asunto(s)

Encefalopatías/fisiopatología , Trastornos Mentales/fisiopatología , Neurobiología , Humanos

RESUMEN

Parkinson's disease is characterized by the progressive loss of midbrain dopamine neurons. Dopamine replacement therapy with levodopa alleviates parkinsonian motor symptoms but is complicated by the development of involuntary movements, termed levodopa-induced dyskinesia (LID). Aberrant activity in the striatum has been hypothesized to cause LID. Here, to establish a direct link between striatal activity and dyskinesia, we combine optogenetics and a method to manipulate dyskinesia-associated neurons, targeted recombination in active populations (TRAP). We find that TRAPed cells are a stable subset of sensorimotor striatal neurons, predominantly from the direct pathway, and that reactivation of TRAPed striatal neurons causes dyskinesia in the absence of levodopa. Inhibition of TRAPed cells, but not a nonspecific subset of direct pathway neurons, ameliorates LID. These results establish that a distinct subset of striatal neurons is causally involved in LID and indicate that successful therapeutic strategies for treating LID may require targeting functionally selective neuronal subtypes.

Asunto(s)

Antiparkinsonianos/administración & dosificación , Cuerpo Estriado/fisiopatología , Discinesia Inducida por Medicamentos/fisiopatología , Levodopa/administración & dosificación , Neuronas/fisiología , Enfermedad de Parkinson/fisiopatología , Animales , Cuerpo Estriado/efectos de los fármacos , Modelos Animales de Enfermedad , Femenino , Masculino , Ratones Endogámicos C57BL , Ratones Transgénicos , Corteza Motora/efectos de los fármacos , Corteza Motora/fisiopatología , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/fisiopatología , Neuronas/efectos de los fármacos , Optogenética

RESUMEN

Fast-spiking interneurons (FSIs) are a prominent class of forebrain GABAergic cells implicated in two seemingly independent network functions: gain control and network plasticity. Little is known, however, about how these roles interact. Here, we use a combination of cell-type-specific ablation, optogenetics, electrophysiology, imaging, and behavior to describe a unified mechanism by which striatal FSIs control burst firing, calcium influx, and synaptic plasticity in neighboring medium spiny projection neurons (MSNs). In vivo silencing of FSIs increased bursting, calcium transients, and AMPA/NMDA ratios in MSNs. In a motor sequence task, FSI silencing increased the frequency of calcium transients but reduced the specificity with which transients aligned to individual task events. Consistent with this, ablation of FSIs disrupted the acquisition of striatum-dependent egocentric learning strategies. Together, our data support a model in which feedforward inhibition from FSIs temporally restricts MSN bursting and calcium-dependent synaptic plasticity to facilitate striatum-dependent sequence learning.

Asunto(s)

Señalización del Calcio/fisiología , Interneuronas/metabolismo , Aprendizaje/fisiología , Red Nerviosa/metabolismo , Plasticidad Neuronal/fisiología , Animales , Interneuronas/citología , Ratones , Ratones Transgénicos , N-Metilaspartato/metabolismo , Red Nerviosa/citología , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/metabolismo

RESUMEN

Neurological disease drives symptoms through pathological changes to circuit functions. Therefore, understanding circuit mechanisms that drive behavioral dysfunction is of critical importance for quantitative diagnosis and systematic treatment of neurological disease. Here, we describe key technologies that enable measurement and manipulation of neural activity and neural circuits. Applying these approaches led to the discovery of circuit mechanisms underlying pathological motor behavior, arousal regulation, and protein accumulation. Finally, we discuss how optogenetic functional magnetic resonance imaging reveals global scale circuit mechanisms, and how circuit manipulations could lead to new treatments of neurological diseases.

Asunto(s)

Imagen por Resonancia Magnética/métodos , Imagen Molecular/métodos , Vías Nerviosas/anatomía & histología , Animales , Encéfalo/fisiología , Humanos , Enfermedades del Sistema Nervioso/diagnóstico por imagen , Vías Nerviosas/diagnóstico por imagen , Optogenética

RESUMEN

Typical antipsychotics can cause disabling side effects. Specifically, antagonism of D2R signaling by the typical antipsychotic haloperidol induces parkinsonism in humans and catalepsy in rodents. Striatal dopamine D2 receptors (D2R) are major regulators of motor activity through their signaling on striatal projection neurons and interneurons. We show that D2R signaling on cholinergic interneurons contributes to an in vitro pause in firing of these otherwise tonically active neurons and to the striatal dopamine/acetylcholine balance. The selective ablation of D2R from cholinergic neurons allows discrimination between the motor-reducing and cataleptic effects of antipsychotics. The cataleptic effect of antipsychotics is triggered by blockade of D2R on cholinergic interneurons and the consequent increase of acetylcholine signaling on striatal projection neurons. These studies illuminate the critical role of D2R-mediated signaling in regulating the activity of striatal cholinergic interneurons and the mechanisms of typical antipsychotic side effects.

Asunto(s)

Antipsicóticos/farmacología , Neuronas Colinérgicas/efectos de los fármacos , Cuerpo Estriado/efectos de los fármacos , Interneuronas/efectos de los fármacos , Trastornos Parkinsonianos/tratamiento farmacológico , Acetilcolina/metabolismo , Animales , Colinérgicos/farmacología , Neuronas Colinérgicas/metabolismo , Dopamina/metabolismo , Ratones Transgénicos , Neostriado/metabolismo , Receptores de Dopamina D2/efectos de los fármacos , Receptores de Dopamina D2/metabolismo , Transducción de Señal/efectos de los fármacos

RESUMEN

A central theory of basal ganglia function is that striatal neurons expressing the D1 and D2 dopamine receptors exert opposing brain-wide influences. However, the causal influence of each population has never been measured at the whole-brain scale. Here, we selectively stimulated D1 or D2 receptor-expressing neurons while visualizing whole-brain activity with fMRI. Excitation of either inhibitory population evoked robust positive BOLD signals within striatum, while downstream regions exhibited significantly different and generally opposing responses consistent with-though not easily predicted from-contemporary models of basal ganglia function. Importantly, positive and negative signals within the striatum, thalamus, GPi, and STN were all associated with increases and decreases in single-unit activity, respectively. These findings provide direct evidence for the opposing influence of D1 and D2 receptor-expressing striatal neurons on brain-wide circuitry and extend the interpretability of fMRI studies by defining cell-type-specific contributions to the BOLD signal.

Asunto(s)

Ganglios Basales/fisiología , Vías Nerviosas/fisiología , Neuronas/fisiología , Animales , Ratones Transgénicos , Modelos Neurológicos , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo

RESUMEN

Movement suppression in Parkinson's disease (PD) is thought to arise from increased efficacy of the indirect pathway basal ganglia circuit, relative to the direct pathway. However, the underlying pathophysiological mechanisms remain elusive. To examine whether changes in the strength of synaptic inputs to these circuits contribute to this imbalance, we obtained paired whole-cell recordings from striatal direct- and indirect-pathway medium spiny neurons (dMSNs and iMSNs) and optically stimulated inputs from sensorimotor cortex or intralaminar thalamus in brain slices from control and dopamine-depleted mice. We found that dopamine depletion selectively decreased synaptic strength at thalamic inputs to dMSNs, suggesting that thalamus drives asymmetric activation of basal ganglia circuitry underlying parkinsonian motor impairments. Consistent with this hypothesis, in vivo chemogenetic and optogenetic inhibition of thalamostriatal terminals reversed motor deficits in dopamine-depleted mice. These results implicate thalamostriatal projections in the pathophysiology of PD and support interventions targeting thalamus as a potential therapeutic strategy.

Asunto(s)

Cuerpo Estriado/patología , Vías Nerviosas/fisiología , Trastornos Parkinsonianos/patología , Sinapsis/fisiología , Tálamo/patología , Adrenérgicos/toxicidad , Animales , Modelos Animales de Enfermedad , Agonistas de Aminoácidos Excitadores/farmacología , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Potenciales Postsinápticos Excitadores/genética , Conducta Exploratoria , Lateralidad Funcional , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Haz Prosencefálico Medial/lesiones , Ratones , N-Metilaspartato/farmacología , Oxidopamina/toxicidad , Trastornos Parkinsonianos/inducido químicamente , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Tirosina 3-Monooxigenasa/metabolismo , Proteína 2 de Transporte Vesicular de Glutamato/genética , Proteína 2 de Transporte Vesicular de Glutamato/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiónico/farmacología

RESUMEN

The basal ganglia (BG) are critical for adaptive motor control, but the circuit principles underlying their pathway-specific modulation of target regions are not well understood. Here, we dissect the mechanisms underlying BG direct and indirect pathway-mediated control of the mesencephalic locomotor region (MLR), a brainstem target of BG that is critical for locomotion. We optogenetically dissect the locomotor function of the three neurochemically distinct cell types within the MLR: glutamatergic, GABAergic, and cholinergic neurons. We find that the glutamatergic subpopulation encodes locomotor state and speed, is necessary and sufficient for locomotion, and is selectively innervated by BG. We further show activation and suppression, respectively, of MLR glutamatergic neurons by direct and indirect pathways, which is required for bidirectional control of locomotion by BG circuits. These findings provide a fundamental understanding of how BG can initiate or suppress a motor program through cell-type-specific regulation of neurons linked to specific actions.

Asunto(s)

Ganglios Basales/fisiología , Mapeo Encefálico , Mesencéfalo/citología , Actividad Motora , Vías Nerviosas , Animales , Neuronas GABAérgicas/citología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Neuronas/fisiología , Optogenética

RESUMEN

Circuit dysfunction models of psychiatric disease posit that pathological behavior results from abnormal patterns of electrical activity in specific cells and circuits in the brain. Many psychiatric disorders are associated with abnormal activity in the prefrontal cortex and in the basal ganglia, a set of subcortical nuclei implicated in cognitive and motor control. Here we discuss the role of the basal ganglia and connected prefrontal regions in the etiology and treatment of obsessive-compulsive disorder, anxiety, and depression, emphasizing mechanistic work in rodent behavioral models to dissect causal cortico-basal ganglia circuits underlying discrete behavioral symptom domains relevant to these complex disorders.

Asunto(s)

Ganglios Basales/fisiopatología , Trastornos Mentales/fisiopatología , Vías Nerviosas/fisiopatología , Corteza Prefrontal/fisiopatología , Animales , Humanos

RESUMEN

In this issue of Neuron, Sippy et al. (2015) provide the clearest evidence to date that information is differentially encoded in the direct and indirect pathways of the striatum. The results support the classical notion that the direct pathway plays a critical role in initiating actions.

Asunto(s)

Cuerpo Estriado/citología , Cuerpo Estriado/fisiología , Objetivos , Neuronas/fisiología , Desempeño Psicomotor/fisiología , Recompensa , Animales

Asunto(s)

Neuronas/metabolismo , Optogenética/tendencias , Potenciales de Acción/fisiología , Animales , Channelrhodopsins , Humanos , Optogenética/métodos

RESUMEN

The basal ganglia are a series of interconnected subcortical nuclei. The function and dysfunction of these nuclei have been studied intensively in motor control, but more recently our knowledge of these functions has broadened to include prominent roles in cognition and affective control. This review summarizes historical models of basal ganglia function, as well as findings supporting or conflicting with these models, while emphasizing recent work in animals and humans directly testing the hypotheses generated by these models.

Asunto(s)

Enfermedades de los Ganglios Basales/fisiopatología , Ganglios Basales/fisiología , Ganglios Basales/fisiopatología , Modelos Neurológicos , Animales , Humanos , Vías Nerviosas/fisiología , Vías Nerviosas/fisiopatología