An octopamine-specific GRAB sensor reveals a monoamine relay circuitry that boosts aversive learning.

Octopamine (OA), analogous to norepinephrine in vertebrates, is an essential monoamine neurotransmitter in invertebrates that plays a significant role in various biological functions, including olfactory associative learning. However, the spatial and temporal dynamics of OA in vivo remain poorly understood due to limitations associated with the currently available methods used to detect it. To overcome these limitations, we developed a genetically encoded GPCR activation-based (GRAB) OA sensor called GRABOA1.0. This sensor is highly selective for OA and exhibits a robust and rapid increase in fluorescence in response to extracellular OA. Using GRABOA1.0, we monitored OA release in the Drosophila mushroom body (MB), the fly's learning center, and found that OA is released in response to both odor and shock stimuli in an aversive learning model. This OA release requires acetylcholine (ACh) released from Kenyon cells, signaling via nicotinic ACh receptors. Finally, we discovered that OA amplifies aversive learning behavior by augmenting dopamine-mediated punishment signals via Octß1R in dopaminergic neurons, leading to alterations in synaptic plasticity within the MB. Thus, our new GRABOA1.0 sensor can be used to monitor OA release in real-time under physiological conditions, providing valuable insights into the cellular and circuit mechanisms that underlie OA signaling.

Improved green and red GRAB sensors for monitoring spatiotemporal serotonin release in vivo.

The serotonergic system plays important roles in both physiological and pathological processes, and is a therapeutic target for many psychiatric disorders. Although several genetically encoded GFP-based serotonin (5-HT) sensors were recently developed, their sensitivities and spectral profiles are relatively limited. To overcome these limitations, we optimized green fluorescent G-protein-coupled receptor (GPCR)-activation-based 5-HT (GRAB5-HT) sensors and developed a red fluorescent GRAB5-HT sensor. These sensors exhibit excellent cell surface trafficking and high specificity, sensitivity and spatiotemporal resolution, making them suitable for monitoring 5-HT dynamics in vivo. Besides recording subcortical 5-HT release in freely moving mice, we observed both uniform and gradient 5-HT release in the mouse dorsal cortex with mesoscopic imaging. Finally, we performed dual-color imaging and observed seizure-induced waves of 5-HT release throughout the cortex following calcium and endocannabinoid waves. In summary, these 5-HT sensors can offer valuable insights regarding the serotonergic system in both health and disease.

Effects of pressure on microstructure evolution of liquid Fe-S-Bi alloy during rapid solidification: A molecular dynamics study.

To understand the effects of pressure on microstructural evolution, a molecular dynamics simulation study has been performed under pressures of 0-20 GPa for liquid Fe-S-Bi alloy during the solidification process. The variations in the radial distribution function, average atomic energy, and H-A bond index of the cooling system are analyzed. The rapid solidification process of liquid Fe-S-Bi alloy into crystalline and amorphous alloys is investigated from different perspective. The results show that the glass transition temperature Tg, the sizes of the MnS atomic groups, and major bond-types increase almost linearly with increasing pressure. In addition, the recovery rate of Bi increased first and then decreased with increasing pressure, reaching a peak of 68.97% under 5 GPa. The manganese sulfide compound is embedded in the alloy with a spindle-shape under 20 GPa, which is a better clusters structure.

Local 5-HT signaling bi-directionally regulates the coincidence time window for associative learning.

The coincidence between conditioned stimulus (CS) and unconditioned stimulus (US) is essential for associative learning; however, the mechanism regulating the duration of this temporal window remains unclear. Here, we found that serotonin (5-HT) bi-directionally regulates the coincidence time window of olfactory learning in Drosophila and affects synaptic plasticity of Kenyon cells (KCs) in the mushroom body (MB). Utilizing GPCR-activation-based (GRAB) neurotransmitter sensors, we found that KC-released acetylcholine (ACh) activates a serotonergic dorsal paired medial (DPM) neuron, which in turn provides inhibitory feedback to KCs. Physiological stimuli induce spatially heterogeneous 5-HT signals, which proportionally gate the intrinsic coincidence time windows of different MB compartments. Artificially reducing or increasing the DPM neuron-released 5-HT shortens or prolongs the coincidence window, respectively. In a sequential trace conditioning paradigm, this serotonergic neuromodulation helps to bridge the CS-US temporal gap. Altogether, we report a model circuitry for perceiving the temporal coincidence and determining the causal relationship between environmental events.

Effects of MnS inclusions on mechanical behavior and damage mechanism of free-cutting steel: A molecular dynamics study.

In order to research the effect pattern of MnS inclusions on free-cutting steel, we study the microstructure evolution, the damage mechanism and the mechanical properties in free-cutting steel in the presence of MnS inclusions. Spindle shaped MnS is added as inclusions within the free-cutting steel. The mechanical properties were found to change when inclusions were present. The gained results show that the formation of voids causing fracture starts from the interface inside the matrix close to the MnS. From the point of view of nanocomposite strength, the main effect of MnS inclusions is related to stress concentration, leading to the effect of increased stresses near the interface between the interior of the matrix and the inclusions. The inclusions have lower Young's modulus and lower dislocation activity, resulting in smaller deformation of the alloy system, larger interfacial stress concentrations and earlier hole formation. The maximum strain and stress regions of the alloy also appear near the MnS inclusions, which leads to the formation of defects near the MnS inclusions and then fracture of the alloy. MnS inclusions adversely affect the tensile properties of the alloy, such as Young's modulus, yield stress and yield strain. By comparing the stress-strain curves of single crystal iron and alloy containing MnS inclusions, it is indicated that the yield strength of the latter decreases. Slip bands and dislocation lines are first generated around the MnS inclusion, and the phase transition is induced from the original single BCC structure to FCC, HCP and amorphous structures, and the atoms of FCC, HCP and amorphous structures increase with increasing strain, while those of BCC structure decrease, especially after yield strain. This study is significant for understanding the effect of inclusions on the mechanical laws and fracture mechanisms of the alloy.

The measurement, sources of variation, and factors influencing the coupled and coordinated development of rural revitalization and digital economy in China.

An evaluation index system for the coupled and coordinated development of China's digital economy and rural revitalization, including a total of 46 indicators for the digital economy and rural revitalization subsystems, was constructed and combined with the entropy weight method, the coupling coordination degree model, Zhou's constraint identification index, the Dagum Gini coefficient decomposition method, and the panel spatial econometric model to analyze the level of coupled and coordinated development of China's digital economy and rural revitalization. The results found that: (1) the coupling and coordination between the two have gradually improved. The constraints of the digital economy on rural revitalization were gradually alleviated from 2011 to 2015, but after the 19th Party Congress, the development trend of rural revitalization has significantly outstripped the digital economy. (2) the spatial differences in the degree of coupling and coordination between the two are dominated by inter-regional differences and show significant spatial convergence and spatial correlation. Differentiated digital economy development strategies and more radiation in polarized areas are important for reducing regional differences in the level of coupling and coordination between the digital economy and rural revitalization. This will help China's digital countryside grow more efficiently.

Next-generation GRAB sensors for monitoring dopaminergic activity in vivo.

Dopamine (DA) plays a critical role in the brain, and the ability to directly measure dopaminergic activity is essential for understanding its physiological functions. We therefore developed red fluorescent G-protein-coupled receptor-activation-based DA (GRABDA) sensors and optimized versions of green fluorescent GRABDA sensors. In response to extracellular DA, both the red and green GRABDA sensors exhibit a large increase in fluorescence, with subcellular resolution, subsecond kinetics and nanomolar-to-submicromolar affinity. Moreover, the GRABDA sensors resolve evoked DA release in mouse brain slices, detect evoked compartmental DA release from a single neuron in live flies and report optogenetically elicited nigrostriatal DA release as well as mesoaccumbens dopaminergic activity during sexual behavior in freely behaving mice. Coexpressing red GRABDA with either green GRABDA or the calcium indicator GCaMP6s allows tracking of dopaminergic signaling and neuronal activity in distinct circuits in vivo.