RESUMO
Orexins (also called hypocretins) are hypothalamic neuropeptides that carry out essential functions in the central nervous system; however, little is known about their release and range of action in vivo owing to the limited resolution of current detection technologies. Here we developed a genetically encoded orexin sensor (OxLight1) based on the engineering of circularly permutated green fluorescent protein into the human type-2 orexin receptor. In mice OxLight1 detects optogenetically evoked release of endogenous orexins in vivo with high sensitivity. Photometry recordings of OxLight1 in mice show rapid orexin release associated with spontaneous running behavior, acute stress and sleep-to-wake transitions in different brain areas. Moreover, two-photon imaging of OxLight1 reveals orexin release in layer 2/3 of the mouse somatosensory cortex during emergence from anesthesia. Thus, OxLight1 enables sensitive and direct optical detection of orexin neuropeptides with high spatiotemporal resolution in living animals.
Assuntos
Encéfalo/metabolismo , Imagem Molecular/métodos , Receptores de Orexina/genética , Orexinas/análise , Proteínas Recombinantes/metabolismo , Animais , Comportamento Animal , Feminino , Células HEK293 , Humanos , Masculino , Camundongos Endogâmicos C57BL , Receptores de Orexina/metabolismo , Orexinas/genética , Orexinas/farmacologia , Fótons , Proteínas Recombinantes/genética , Reprodutibilidade dos Testes , Sono/fisiologiaRESUMO
Learning to fear danger is essential for survival. However, overactive, relapsing fear behavior in the absence of danger is a hallmark of disabling anxiety disorders that affect millions of people. Its suppression is thus of great interest, but the necessary brain components remain incompletely identified. We studied fear suppression through a procedure in which, after acquiring fear of aversive events (fear learning), subjects were exposed to fear-eliciting cues without aversive events (safety learning), leading to suppression of fear behavior (fear extinction). Here we show that inappropriate, learning-resistant fear behavior results from disruption of brain components not previously implicated in this disorder: hypothalamic melanin-concentrating hormone-expressing neurons (MNs). Using real-time recordings of MNs across fear learning and extinction, we provide evidence that fear-inducing aversive events elevate MN activity. We find that optogenetic disruption of this MN activity profoundly impairs safety learning, abnormally slowing down fear extinction and exacerbating fear relapse. Importantly, we demonstrate that the MN disruption impairs neither fear learning nor related sensory responses, indicating that MNs differentially control safety and fear learning. Thus, we identify a neural substrate for inhibition of excessive fear behavior.
Assuntos
Extinção Psicológica/fisiologia , Medo/fisiologia , Hormônios Hipotalâmicos/metabolismo , Hipotálamo/citologia , Melaninas/metabolismo , Neurônios/metabolismo , Hormônios Hipofisários/metabolismo , Animais , Hipotálamo/metabolismo , Masculino , Camundongos , OptogenéticaRESUMO
Damage to the lateral hypothalamus (LH) causes profound physical inactivity in mammals. Several molecularly distinct types of LH neurons have been identified, including orexin cells and glutamic acid decarboxylase 65 (GAD65) cells, but their interplay in orchestrating physical activity is not fully understood. Here, using optogenetic circuit analysis and cell type-specific deep-brain recordings in behaving mice, we show that orexin cell activation rapidly recruits GAD65LH neurons. We demonstrate that internally initiated GAD65LH cell bursts precede and accompany spontaneous running bouts, that selective chemogenetic silencing of natural GAD65LH cell activity depresses voluntary locomotion, and that GAD65LH cell overactivation leads to hyperlocomotion. These results thus identify a molecularly distinct, orexin-activated LH submodule that governs physical activity in mice.
Assuntos
Glutamato Descarboxilase/metabolismo , Região Hipotalâmica Lateral/fisiologia , Atividade Motora/fisiologia , Orexinas/fisiologia , Animais , Eletrocardiografia , Técnicas de Transferência de Genes , Glutamato Descarboxilase/genética , Masculino , CamundongosRESUMO
To successfully navigate the environment, animals depend on their ability to continuously track their heading direction and speed. Neurons that encode angular head velocity (AHV) are fundamental to this process, yet the contribution of various motion signals to AHV coding in the cortex remains elusive. By performing chronic single-unit recordings in the retrosplenial cortex (RSP) of the mouse and tracking the activity of individual AHV cells between freely moving and head-restrained conditions, we find that vestibular inputs dominate AHV signaling. Moreover, the addition of visual inputs onto these neurons increases the gain and signal-to-noise ratio of their tuning during active exploration. Psychophysical experiments and neural decoding further reveal that vestibular-visual integration increases the perceptual accuracy of angular self-motion and the fidelity of its representation by RSP ensembles. We conclude that while cortical AHV coding requires vestibular input, where possible, it also uses vision to optimize heading estimation during navigation.
Assuntos
Percepção de Movimento , Vestíbulo do Labirinto , Animais , Giro do Cíngulo/fisiologia , Movimentos da Cabeça/fisiologia , Camundongos , Percepção de Movimento/fisiologia , Neurônios/fisiologia , Vestíbulo do Labirinto/fisiologiaRESUMO
The lateral hypothalamus (LH) is critical for generating context-appropriate actions. LH deficits uncouple behaviour and motor control from internal and external environmental influences. Non-specific LH lesions produce apathy, akinesia, and weight loss. Targeted impairments of brain-wide-projecting LH cells, such as orexin or GABA neurons, result in context-inappropriate arousal and motor control, and pathological eating. Generating timely adaptive actions requires timely updating of neural representations of context. Here we review how activity patterns of different LH neurons represent rapid external events on subsecond timescales. We discuss experience-dependent plasticity of these representations and their impact on wider neural processing and sensorimotor control, with a focus on LH orexin neurons. We highlight key questions, such as neural origins of rapid LH dynamics, and whether LH encodes sensory or motor activity. Real-time monitoring of fast LH dynamics during learning will be vital for understanding the elusive algorithms that allow the brain to combine fast and slow variables to guide actions.
Assuntos
Região Hipotalâmica Lateral , Neuropeptídeos , Nível de Alerta , Neurônios GABAérgicos , Região Hipotalâmica Lateral/metabolismo , Hipotálamo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Neuropeptídeos/metabolismo , OrexinasRESUMO
Appropriate motor control is critical for normal life, and requires hypothalamic hypocretin/orexin neurons (HONs). HONs are slowly regulated by nutrients, but also display rapid (subsecond) activity fluctuations in vivo. The necessity of these activity bursts for sensorimotor control and their roles in specific phases of movement are unknown. Here we show that temporally-restricted optosilencing of spontaneous or sensory-evoked HON bursts disrupts locomotion initiation, but does not affect ongoing locomotion. Conversely, HON optostimulation initiates locomotion with subsecond delays in a frequency-dependent manner. Using 2-photon volumetric imaging of activity of >300 HONs during sensory stimulation and self-initiated locomotion, we identify several locomotion-related HON subtypes, which distinctly predict the probability of imminent locomotion initiation, display distinct sensory responses, and are differentially modulated by food deprivation. By causally linking HON bursts to locomotion initiation, these findings reveal the sensorimotor importance of rapid spontaneous and evoked fluctuations in HON ensemble activity.
Assuntos
Hipotálamo/fisiologia , Locomoção/fisiologia , Neurônios/fisiologia , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Orexinas/metabolismoRESUMO
To interpret visual-motion events, the underlying computation must involve internal reference to the motion status of the observer's head. We show here that layer 6 (L6) principal neurons in mouse primary visual cortex (V1) receive a diffuse, vestibular-mediated synaptic input that signals the angular velocity of horizontal rotation. Behavioral and theoretical experiments indicate that these inputs, distributed over a network of 100 L6 neurons, provide both a reliable estimate and, therefore, physiological separation of head-velocity signals. During head rotation in the presence of visual stimuli, L6 neurons exhibit postsynaptic responses that approximate the arithmetic sum of the vestibular and visual-motion response. Functional input mapping reveals that these internal motion signals arrive into L6 via a direct projection from the retrosplenial cortex. We therefore propose that visual-motion processing in V1 L6 is multisensory and contextually dependent on the motion status of the animal's head.
Assuntos
Movimentos da Cabeça/fisiologia , Percepção de Movimento/fisiologia , Rede Nervosa/fisiologia , Estimulação Luminosa/métodos , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Rede Nervosa/química , Córtex Visual/química , Vias Visuais/químicaRESUMO
Lesion experiments suggest that odour input to the olfactory bulb contains significant redundant signal such that rodents can discern odours using minimal stimulus-related information. Here we investigate the dependence of odour-quality perception on the integrity of glomerular activity by comparing odour-evoked activity maps before and after epithelial lesions. Lesions prevent mice from recognizing previously experienced odours and differentially delay discrimination learning of unrecognized and novel odour pairs. Poor recognition results not from mice experiencing an altered concentration of an odour but from perception of apparent novel qualities. Consistent with this, relative intensity of glomerular activity following lesions is altered compared with maps recorded in shams and by varying odour concentration. Together, these data show that odour recognition relies on comprehensively matching input patterns to a previously generated stimulus template. When encountering novel odours, access to all glomerular activity ensures rapid generation of new templates to perform accurate perceptual judgements.
Assuntos
Julgamento/fisiologia , Odorantes , Percepção/fisiologia , Olfato/fisiologia , Animais , Aprendizagem por Discriminação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mucosa Nasal/patologia , Estimulação Física , Reconhecimento Psicológico , Sulfato de ZincoRESUMO
Cerebellar granule cells are an attractive model system for examining synaptic transmission and temporal integration, because of their small number of excitatory synaptic inputs and electrotonic compactness. Recent in vivo whole-cell recordings have revealed how sensory stimuli are represented by synaptic activity across multiple modalities and cerebellar regions. By monitoring the activity of individual synapses, the reliability of these unitary signals has been quantified, and the complexity of a granule cell's receptive field has been explored at the highest resolution. Here we describe the emerging principles of synaptic sensory representation and their consequences for information processing in the granule cell layer.