Sensory detection of food rapidly modulates arcuate feeding circuits.

Hunger is controlled by specialized neural circuits that translate homeostatic needs into motivated behaviors. These circuits are under chronic control by circulating signals of nutritional state, but their rapid dynamics on the timescale of behavior remain unknown. Here, we report optical recording of the natural activity of two key cell types that control food intake, AgRP and POMC neurons, in awake behaving mice. We find unexpectedly that the sensory detection of food is sufficient to rapidly reverse the activation state of these neurons induced by energy deficit. This rapid regulation is cell-type specific, modulated by food palatability and nutritional state, and occurs before any food is consumed. These data reveal that AgRP and POMC neurons receive real-time information about the availability of food in the external world, suggesting a primary role for these neurons in controlling appetitive behaviors such as foraging that promote the discovery of food.

Fluorescence-guided thoracoscopic surgery for postoperative chylothorax: A technical note with video vignette.

TECHNIQUE: The surgical management for high-output postoperative chylothorax typically necessitates ligation of the thoracic duct (TD) above the leak site and/or sealing the leak with a clip. However, pinpointing these structures during subsequent surgeries can be challenging due to their variable course and the presence of traumatized tissues surrounding the leak area. In response to this, we have developed a novel, fluorescence-guided technique that significantly enhances intraoperative identification of the leak point and the TD. This method was applied in the case of a 52-year-old man suffering from refractory chylothorax following a previous lung cancer surgery. This study documents the surgical procedure and includes a video vignette for a comprehensive understanding. RESULTS: A bilateral inguinal lymph node injection of saline (10 mL), guided by ultrasound and containing 2.5 mg/mL indocyanine green (ICG), was administered 20 min prior to surgery. During thoracoscopic exploration, the leak point was precisely pinpointed in the right paratracheal area by transitioning from bright light to fluorescent mode. The TD was clearly identified, and upon ligation, there was no further leakage of fluorescent lymph, indicating a successful closure of the lymphatic structure. The surgery proceeded uneventfully, and the patient was able to resume oral intake on the third postoperative day. There was no evidence of recurring symptoms, leading to his discharge. CONCLUSION: The intralymphatic injection of ICG offers a rapid visualization of the TD's anatomy and can effectively pinpoint the leak point, even amidst traumatized tissues. Moreover, it provides prompt feedback on the efficacy of ligation.

GABA is depolarizing in hippocampal dentate granule cells of the adolescent and adult rats.

GABAergic signaling in hippocampal pyramidal neurons undergoes a switch from depolarizing to hyperpolarizing during early neuronal development. Whether such a transformation of GABAergic action occurs in dentate granule cells (DGCs), located at the first stage of the hippocampal trisynaptic circuit, is unclear. Here, we use noninvasive extracellular recording to monitor the effect of synaptically released GABA on the DGC population. We find that GABAergic responses in adolescent and adult rat DGCs are still depolarizing from rest. Using a morphologically realistic DGC model, we show that GABAergic action, depending on its precise timing and location, can have either an excitatory or inhibitory role in signal processing in the dentate gyrus.

Ba2+- and bupivacaine-sensitive background K+ conductances mediate rapid EPSP attenuation in oligodendrocyte precursor cells.

Glutamatergic transmission onto oligodendrocyte precursor cells (OPCs) may regulate OPC proliferation, migration and differentiation. Dendritic integration of excitatory postsynaptic potentials (EPSPs) is critical for neuronal functions, and mechanisms regulating dendritic propagation and summation of EPSPs are well understood. However, little is known about EPSP attenuation and integration in OPCs. We developed realistic OPC models for synaptic integration, based on passive membrane responses of OPCs obtained by simultaneous dual whole-cell patch-pipette recordings. Compared with neurons, OPCs have a very low value of membrane resistivity, which is largely mediated by Ba(2+)- and bupivacaine-sensitive background K(+) conductances. The very low membrane resistivity not only leads to rapid EPSP attenuation along OPC processes but also sharpens EPSPs and narrows the temporal window for EPSP summation. Thus, background K(+) conductances regulate synaptic responses and integration in OPCs, thereby affecting activity-dependent neuronal control of OPC development and function.

Soma-Targeted Imaging of Neural Circuits by Ribosome Tethering.

Neuroscience relies on techniques for imaging the structure and dynamics of neural circuits, but the cell bodies of individual neurons are often obscured by overlapping fluorescence from axons and dendrites in surrounding neuropil. Here, we describe two strategies for using the ribosome to restrict the expression of fluorescent proteins to the neuronal soma. We show first that a ribosome-tethered nanobody can be used to trap GFP in the cell body, thereby enabling direct visualization of previously undetectable GFP fluorescence. We then design a ribosome-tethered GCaMP for imaging calcium dynamics. We show that this reporter faithfully tracks somatic calcium dynamics in the mouse brain while eliminating cross-talk between neurons caused by contaminating neuropil. In worms, this reporter enables whole-brain imaging with faster kinetics and brighter fluorescence than commonly used nuclear GCaMPs. These two approaches provide a general way to enhance the specificity of imaging in neurobiology.