Loss of CO_2 sensing by the olfactory system of CNGA3 knockout mice

Atmospheric CO_2 can signal the presence of food, predators or environmental stress and trigger stereotypical behaviorsin both vertebrates and invertebrates. Recent studies have shown that the necklace olfactory system in mice sensitively detectsCO_2 in the air. Olfactory CO_2 neurons are believed to rely on cyclic guanosine monophosphate (cGMP) as the key secondmessenger; however, the specific ion channel underlying CO2 responses remains unclear. Here we show that CO_2-evoked neuronaland behavioral responses require cyclic nucleotide-gated (CNG) channels consisting of the CNGA3 subunit. ThroughCa^(2+)-imaging, we found that CO_2-triggered Ca^(2+) influx was abolished in necklace olfactory sensory neurons (OSNs) ofCNGA3-knockout mice. Olfactory detection tests using a Go/No-go paradigm showed that these knockout mice failed to detect0.5% CO_2. Thus, sensitive detection of atmospheric CO_2 depends on the function of CNG channels consisting of the CNGA3subunit in necklace OSNs. These data support the important role of the necklace olfactory system in CO_2 sensing and extend ourunderstanding of the signal transduction pathway mediating CO_2 detection in

All-fiber-transmission photometry for simultaneous optogenetic stimulation and multi-color neuronal activity recording

Manipulating and real-time monitoring of neuronal activities with cell-type specificity and precise spatiotemporal resolution during animal behavior are fundamental technologies for exploring the functional connectivity, information transmission, and physiological functions of neural circuits in vivo. However, current techniques for optogenetic stimulation and neuronal activity recording mostly operate independently. Here, we report an all-fiber-transmission photometry system for simultaneous optogenetic manipulation and multi-color recording of neuronal activities and the neurotransmitter release in a freely moving animal. We have designed and manufactured a wavelength-independent multi-branch fiber bundle to enable simultaneous optogenetic manipulation and multi-color recording at different wavelengths. Further, we combine a laser of narrow linewidth with the lock-in amplification method to suppress the optogenetic stimulation-induced artifacts and channel crosstalk. We show that the collection efficiency of our system outperforms a traditional epi-fluorescence system. Further, we demonstrate successful recording of dynamic dopamine(DA) responses to unexpected rewards in the nucleus accumbens(NAc) in a freely moving mouse. We also show simultaneous dual-color recording of neuronal Ca2+ signals and DA dynamics in the NAc upon delivering an unexpected reward and the simultaneous optogenetic activating at dopaminergic terminals in the same location. Thus, our multi-function fiber photometry system provides a compatible, efficient, and flexible solution for neuroscientists to study neural circuits and neurological diseases.

Long-term Fiber Photometry for Neuroscience Studies

Fiber photometry is a sensitive and easy way to detect changes in fluorescent signals. The combination of fiber photometry with various fluorescent biomarkers has substantially advanced neuroscience research over the last decade. Despite the wide use of fiber photometry in biomedical fields, the lack of a detailed and comprehensive protocol has limited progress and sometimes complicated the interpretation of data. Here, we describe detailed procedures of fiber photometry for the long-term monitoring of neuronal activity in freely-behaving animals, including surgery, apparatus setup, data collection, and analysis.

An optical brain-to-brain interface supports rapid information transmission for precise locomotion control

Brain-to-brain interfaces(BtBIs) hold exciting potentials for direct communication between individual brains. However,technical challenges often limit their performance in rapid information transfer. Here, we demonstrate an optical brain-to-brain interface that transmits information regarding locomotor speed from one mouse to another and allows precise, real-time control of locomotion across animals with high information transfer rate. We found that the activity of the genetically identified neuromedin B(NMB) neurons within the nucleus incertus(NI) precisely predicts and critically controls locomotor speed. By optically recording Ca2+ signals from the NI of a "Master" mouse and converting them to patterned optogenetic stimulations of the NI of an "Avatar" mouse, the Bt BI directed the Avatar mice to closely mimic the locomotion of their Masters with information transfer rate about two orders of magnitude higher than previous Bt BIs. These results thus provide proof-of-concept that optical Bt BIs can rapidly transmit neural information and control dynamic behaviors across individuals.

Pharmacogenetic activation of midbrain dopaminergic neurons induces hyperactivity

Dopaminergic neurons regulate and organize numerous important behavioral processes including motor activity.Consistently,manipulation of brain dopamine concentrations changes animal activity levels.Dopamine is synthesized by several neuronal populations in the brain.This study was carried out to directly test whether selective activation of dopamine neurons in the midbrain induces hyperactivity.A pharmacogenetic approach was used to activate midbrain dopamine neurons,and behavioral assays were conducted to determine the effects on mouse activity levels.Transgenic expression of the evolved hM3Dq receptor was achieved by infusing Creinducible AAV viral vectors into the midbrain of DATCre mice.Neurons were excited by injecting the hM3Dq ligand clozapine-N-oxide（CNO）.Mouse locomotor activity was measured in an open field.The results showed that CNO selectively activated midbrain dopaminergic neurons and induced hyperactivity in a dose-dependent manner,supporting the idea that these neurons play an important role in regulating motor activity.

Genetically encoded neural activity indicators

Recent years have witnessed the fascinating development of imaging approaches to studying neural activities; this progress has been based on an influx of ideas and methods from molecular biology and optical engineering. Here we review the design and application of genetically encoded indicators for calcium ions, membrane potential and neurotransmitters. We also summarize common strategies for the design and optimization of genetically encoded neural activity indicators.

A neuropsin-based optogenetic tool for precise control of Gq signaling

G_(q)-coupled receptors regulate numerous physiological processes by activating enzymes and inducing intracellular Ca^(2+)signals.There is a strong need for an optogenetic tool that enables powerful experimental control over G_(q) signaling.Here,we present chicken opsin 5(cOpn5)as the long sought-after,single-component optogenetic tool that mediates ultra-sensitive optical control of intracellular G_(q) signaling with high temporal and spatial resolution.Expressing cOpn5 in HEK 293T cells and primary mouse astrocytes enables blue light-triggered,G_(q)-dependent Ca^(2+) release from intracellular stores and protein kinase C activation.Strong Ca^(2+) transients were evoked by brief light pulses of merely 10 ms duration and at 3 orders lower light intensity of that for common optogenetic tools.Photostimulation of cOpn5-expressing cells at the subcellular and single-cell levels generated fast intracellular Ca^(2+)transition,thus demonstrating the high spatial precision of cOpn5 optogenetics.The cOpn5-mediated optogenetics could also be applied to activate neurons and control animal behavior in a circuit-dependent manner.cOpn5 optogenetics may find broad applications in studying the mechanisms and functional relevance of G_(q) signaling in both non-excitable cells and excitable cells in all major organ systems.

A Deep Mesencephalic Nucleus Circuit Regulates Licking Behavior

Licking behavior is important for water intake.The deep mesencephalic nucleus(DpMe)has been implicated in instinctive behaviors.However,whether the DpMe is involved in licking behavior and the precise neural circuit behind this behavior remains unknown.Here,we found that the activity of the DpMe decreased during water intake.Inhibition of vesicular glutamate transporter 2-positive(VGLUT2+)neurons in the DpMe resulted in increased water intake.Somatostatin-expressing(SST+),but not protein kinase C-expressing(PKC-8+),GABAergic neurons in the central amygdala(CeA)preferentially innervated DpMe VGLUT2+neurons.The SST+neurons in the CeA projecting to the DpMe were activated at the onset of licking behavior.Activation of these CeA SST+GABAergic neurons,but not PKC-8+GABAergic neurons,projecting to the DpMe was sufficient to induce licking behavior and promote water intake.These findings redefine the roles of the DpMe and reveal a novel CeAssT_DpMevcLUT?cireuit that regulaes icking behavior and promotes water intake.