The nucleus accumbens (NAcc) may play a major role in opiate dependence, and central NMDA receptors are reported to influence opiate tolerance and dependence. Therefore, we investigated the effects of the selective μ-opioid receptor agonist [ d -Ala 2 - N -Me-Phe 4 ,Gly-ol 5 ]-enkephalin (DAMGO) on membrane properties of rat NAcc neurons and on events mediated by NMDA and non-NMDA glutamate receptors, using intracellular recording in a brain slice preparation. Most NAcc neurons showed a marked inward rectification (correlated with Cs + - and Ba 2+ -sensitive inward relaxations) when hyperpolarized, as well as a slowly depolarizing ramp with positive current pulses. Superfusion of DAMGO did not alter membrane potential, input resistance, or the inward relaxations. In the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) used to block non-NMDA glutamate receptors and bicuculline to block GABA A receptors, EPSPs evoked by local stimulation displayed characteristics of an NMDA component: (1) long duration, (2) voltage sensitivity, and (3) blockade by the NMDA receptor antagonist dl -2-amino-5-phosphonovaleric acid ( d -APV). DAMGO (0.1–1 μ m ) significantly decreased both NMDA- and non-NMDA–EPSP amplitudes with reversal of this effect by naloxone and the μ-selective antagonist [Cys 2 -Tyr 3 -Orn 5 -Pen 7 ]-somatostatinamide (CTOP). To assess a postsynaptic action of DAMGO, we superfused slices with tetrodotoxin and evoked inward currents by local application of glutamate agonists. Surprisingly, 0.1–1 μ m DAMGO markedly enhanced the NMDA currents (with reversal by CTOP) but reduced the non-NMDA currents. At higher concentrations (5 μ m ), DAMGO reduced NMDA currents, but this effect was enhanced, not blocked, by CTOP. These results indicate a complex DAMGO modulation of the NMDA component of glutamatergic synaptic transmission in NAcc: μ receptor activation decreases NMDA–EPSP amplitudes presynaptically yet increases NMDA currents postsynaptically. These new data may provide a cellular mechanism for the previously reported role of NMDA receptors in opiate tolerance and dependence.
Ternary two-dimensional (2D) monoclinic Nb2SiTe4 has garnered significant attention for its potential applications in anisotropic photoelectronics. Yet, its intrinsic indirect bandgap nature and low hole mobility, attributed to the short Nb–Nb dimer configurations, hinder the efficient photogenerated carrier separation and transport. In this Letter, using density functional theory calculations, we demonstrate the interlayer intercalation of Si results in the formation of a metastable orthorhombic Nb2SiTe4 structure devoid of detrimental short Nb–Nb dimers. Notably, this Si intercalation leads to a remarkable reduction of hole effective masses of orthorhombic Nb2SiX4 (X = S, Se, and Te), a crucial factor for achieving high carrier mobility. Taking the orthorhombic Nb2SiTe4 monolayer as an example, the calculated hole mobility (>100 cm2 V−1 s−1) is comparable in magnitude to the respectable hole mobility observed in multiple layers of the monoclinic Nb2SiTe4. To simultaneously enhance electron and hole mobility, we establish a van der Waals junction between the monoclinic and orthorhombic Nb2SiTe4 structures, achieving high and comparable carrier mobilities. The Nb2SiTe4 junction exhibits a nearly direct bandgap of 0.35 eV, rendering it suitable for infrared light harvesting. Furthermore, carriers within the Nb2SiTe4 junction become spatially separated across different layers, resulting in an intrinsic built-in electric field, which is superior for efficient photo-generated charge separation and decreases the potential nonradiative carrier recombination. Our findings highlight the impact of cation coordination engineering on the electronic and optical properties of 2D Nb2SiTe4 and provide a feasible solution to achieve better carrier transport in low-dimensional photovoltaic functionalities.
Polydimethylsiloxane (PDMS) as elastic substrate is widely applied for flexible pressure sensors. Functional materials integrated into the network of PDMS are usually able to enhance particular sensing performance. In this work, carbon nanotubes (CNTs) mixed with nano zinc oxide (nano-ZnO) were used as conductive filler to prepare nano-ZnO/CNTs/PDMS active layer to assemble a flexible film pressure sensor. In the low-pressure range, nano-ZnO/CNTs/PDMS pressure sensor reports a sensitivity of 0.18 kPa-1 and a response time of 45.47 ms. The results confirm that the combination of additive CNTs and nano-ZnO enables the PDMS substrate with improved pressure sensing characteristics. Moreover, the nano-ZnO/CNTs/PDMS sensor sustains a good stability after 6000 cycles. The assembled nano-ZnO/CNTs/PDMS sensor was applied to monitor the movement of varied body parts.
A bstract : Both the nucleus accumbens (NAcc) and central amygdala (CeA) are thought to play roles in tolerance to, and dependence on, abused drugs. Although our past studies in rat brain slices suggested a role for NMDA receptors (NMDARs) in NAcc neurons in the effects of acute and chronic opiate treatment, the cellular and molecular mechanisms remained unclear. Therefore, we examined the effects of morphine dependence on electrophysiological properties of NMDARs in freshly isolated NAcc neurons and on expression of mRNA coding for NR2A‐C subunits using single‐cell RT‐PCR. Chronic morphine did not alter the affinity for NMDAR agonists glutamate, homoquinolinate, or NMDA, but decreased the affinity of the coagonist glycine. Chronic morphine altered the NMDAR inhibition by two NMDAR antagonists, 7‐Cl‐kynurenate and ifenprodil, but not that by d‐APV or Mg 2+ . Chronic morphine accelerated the NMDA current desensitization rate in NAcc neurons. In single‐cell RT‐PCR, chronic morphine predominantly reduced the number of neurons expressing multiple NR2 subunits. Ethanol also alters NMDARs. We found that low ethanol concentrations (IC 50 = 13 mM) inhibited NMDA currents and NMDA‐EPSPs in most NAcc neurons in a slice preparation. NAcc neurons from ethanol‐dependent rats showed enhanced NMDA sensitivity. In CeA neurons, acute ethanol decreased (by 10–25%) non‐NMDA‐ and NMDA‐EPSPs in most neurons. In CeA neurons from ethanol‐dependent rats, acute ethanol decreased the non‐NMDA‐EPSPs to the same extent as in naïve rats, but inhibited (by 30–40%) NMDA‐EPSPs significantly more than in controls, suggesting sensitization to ethanol. Preliminary studies with microdialysis and real‐time PCR analysis support this idea: local ethanol administration in vivo had no effect on glutamate release, but chronic ethanol nearly tripled the expression of NR2B subunits (the most ethanol sensitive) in CeA. These combined findings suggest that changes in glutamatergic transmission in NAcc and CeA may underlie the neuroadaptions that lead to opiate and ethanol dependence.
In their Research Article (“Identifying autism loci and genes by tracing recent shared ancestry,” 11 July 2008, p. [218][1]), E. M. Morrow et al. showed that gene expression associated with autism-spectrum disorders (ASD) is controlled by MEF2 transcription factors and hypothesized that autistic
Suppressing trap-assisted nonradiative losses through passivators is a prerequisite for efficient perovskite light-emitting diodes (PeLEDs). However, the complex bonding between passivators and perovskites severely suppresses the passivation process, which still lacks comprehensive understanding. Herein, the number, category, and degree of bonds between different functional groups and the perovskite are quantitatively assessed to study the passivation dynamics. Functional groups with high electrostatic potential and large steric hindrance prioritize strong bonding with organic cations and halides on the perfect surface, leading to suppressed coordination with bulky defects. By modulating the binding priorities and coordination capacity, hindrance from the intense interaction with perfect perovskite is significantly reduced, leading to a more direct passivation process. Consequently, the near-infrared PeLED without external light out-coupling demonstrates a record external quantum efficiency of 24.3% at a current density of 42 mA cm
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