Potentiation of PIEZO2 mechanically-activated currents in sensory neurons mediates vincristine-induced mechanical hypersensitivity

Vincristine, a widely used chemotherapeutic agent for treating different cancer, often induces severe peripheral neuropathic pain. A common symptom of vincristine-induced peripheral neuropathic pain is mechanical allodynia and hyperalgesia. However, mechanisms underlying vincristine-induced mechanical allodynia and hyperalgesia are not well understood. In the present study, we show with behavioral assessment in rats that vincristine induces mechanical allodynia and hyperalgesia in a PIEZO2 channel-dependent manner since gene knockdown or pharmacological inhibition of PIEZO2 channels alleviates vincristine-induced mechanical hypersensitivity. Electrophysiological results show that vincristine potentiates PIEZO2 rapidly adapting (RA) mechanically-activated (MA) currents in rat dorsal root ganglion (DRG) neurons. We have found that vincristine-induced potentiation of PIEZO2 MA currents is due to the enhancement of static plasma membrane tension (SPMT) of these cells following vincristine treatment. Reducing SPMT of DRG neurons by cytochalasin D (CD), a disruptor of the actin filament, abolishes vincristine-induced potentiation of PIEZO2 MA currents, and suppresses vincristine-induced mechanical hypersensitivity in rats. Collectively, enhancing SPMT and subsequently potentiating PIEZO2 MA currents in primary afferent neurons may be an underlying mechanism responsible for vincristine-induced mechanical allodynia and hyperalgesia in rats. Targeting to inhibit PIEZO2 channels may be an effective analgesic method to attenuate vincristine-induced mechanical hypersensitivity.

Modulation of Dopaminergic Neuronal Excitability by Zinc through the Regulation of Calcium-related Channels

Depending on the intracellular buffering of calcium by chelation, zinc has the following two apparent effects on neuronal excitability: enhancement or reduction. Zinc increased tonic activity in the depolarized state when neurons were intracellularly dialyzed with EGTA but attenuated the neuronal activity when BAPTA was used as an intracellular calcium buffer. This suggests that neuronal excitability can be modulated by zinc, depending on the internal calcium buffering capacity. In this study, we elucidated the mechanisms of zinc-mediated alterations in neuronal excitability and determined the effect of calcium-related channels on zinc-mediated alterations in excitability. The zinc-induced augmentation of firing activity was mediated via the inhibition of small-conductance calcium-activated potassium (SK) channels with not only the contribution of voltage-gated L-type calcium channels (VGCCs) and ryanodine receptors (RyRs), but also through the activation of VGCCs via melastatin-like transient receptor potential channels. We suggest that zinc modulates the dopaminergic neuronal activity by regulating not only SK channels as calcium sensors, but also VGCCs or RyRs as calcium sources. Our results suggest that the cytosolic calcium-buffering capacity can tightly regulate zinc-induced neuronal firing patterns and that local calcium-signaling domains can determine the physiological and pathological state of synaptic activity in the dopaminergic system.

Role of Pre-Synaptic NMDA Receptors in the Modulation of Inhibitory Synaptic Transmission in Sensory-Motor and Visual Cortical Pyramidal Neurons in Brain Slices of Young Epileptic Mice

Background: Previous studies from animal models have shown that pre-synapticNMDA receptors (preNMDARs) are present in the cortex, but the role of inhibition mediated bypreNMDARs during epileptogenesis remains unclear. In this study, we wanted to observe thechanges in GABAergic inhibition through preNMDARs in sensory-motor and visual corticalpyramidal neurons after pilocarpine-induced status epilepticus.Methods: Using a pilocarpine-induced epileptic mouse model, sensory-motor and visualcortical slices were prepared, and the whole-cell patch clamp technique was used to recordspontaneous inhibitory post-synaptic currents (sIPSCs).Results: The primary finding was that the mean amplitude of sIPSC from the sensorymotorcortex increased significantly in epileptic mice when the recording pipette contained MK-801 compared to control mice, whereas the mean sIPSC frequency was not significantly different,indicating that post-synaptic mechanisms are involved. However, there was no significant presynapticinhibition through preNMDARs in the acute brain slices from pilocarpine-inducedepileptic mice.Conclusion: In the acute case of epilepsy, a compensatory mechanism of post-synapticinhibition, possibly from ambient GABA, was observed through changes in the amplitude withoutsignificant changes in the frequency of sIPSC compared to control mice. The role of preNMDARmediatedinhibition in epileptogenesis during the chronic condition or in the juvenile stagewarrants further investigation.

Alizarin activates large-conductance Ca2+-activated K+ channels on renal interlobar arterial vascular smooth muscle cells in Wistar rat / 中国药理学通报

Aim To investage the regulatory effect of alizarin on renal interlobar arterial smooth muscle cells. Method The effect of alizarin on BKCa channels was observed by whole-cell patch clamp recording tech-nique. Results Selective BKCa channel blocker ibTX inhibited alizarin-induced outward current(P<0. 05);single smooth muscle cells were incubated in extracel-lular fluid with no Ca2+ 30 minutes, selective L-Ca2+channel blocker nimodipine, selective calcium ion che-lating agent BAPTA-AM and ryanodine inhibited the a-lizarin-induced BKCa channels current, too ( P <0. 05 ) . Conclusion Alizarin relaxes renales interlobar arterial smooth muscle via activation of L-Ca2+ channel firstly, which lead to Ca2+ flowed into cytoplam, and rising of Ca2+ in cytoplam ryanodine receptor indirect-ly, and BKCa is activated at last.

MODULATORY EFFECT OF CAFFEINE ON GABA-ACTIVATED CURRENT FROM ACUTELY ISOLATED RAT DORSAL ROOT GANGLION NEURONS / 神经解剖学杂志

Whole-cell patch clamp technique was performed on acutely isolated rat dorsal root ganglion (DRG) neurons to investigate the modulatory effect of caffeine on γ-aminobutyric acid (GABA)-activated currents (IGABA). The results showed that the majority of the neurons examined (97.4%, 113/116) were sensitive to GABA. 1-1000 μmol/L GABA activated a concentration-dependent inward current which manifested obvious desensitization. After the neurons were treated with caffeine (0.01-100 μmol/L) prior to the application of GABA (100 μmol/L) for 30 s, GABA-activated membrane currents were obviously inhibited. Caffeine shifted the GABA dose-response curve downward and decreased the maximum response to 57% without changing Kd value. These results indicate that the inhibitory effect is non-competitive. Theophylline showed a similar and stronger inhibitory effect on IGABA. The pretreatment with caffeine (10 μmol/L) inhibited IGABA, which was potentized by diazepam (1 μmol/L). Intracellular application of H-8 almost completely abolished the inhibitory effect of caffeine on IGABA. The present results suggest that caffeine may be able to antagonize the effect of presynaptic inhibition of GABA in primary afferent.

Effect of Anlv Capsule on sodium ion channels in ventricular myocytes of guinea pig / 中华中医药杂志

Objective:To observe the effect of Aalv Capsule on sodium current in guinea pig ventricular myocytes(INa)for exploring the mechanism of its anti-premature beats.Methods:Whole-cell patch-clamp recording technique was used to record the Aalv Capsule for a single cell of sodium currents in guinea pig ventricular myocytes.Results:There was dose-dependent of Aalv Capsule in block of sodium currents and had a certain amount of use-dependent and time-dependent.Conclusion:The role of Aalv Capsule in blocking sodium current block was one of the mechanisms of its in bearing premature.

Electrophysiological properties of retinal ganglion cells in Long Evans rats at different postnatal developmental stages / 第三军医大学学报

Objective To investigate the electrophysiological properties of retinal ganglion cells(RGCs) in Long Evans rats during different postnatal developmental stages so as to explore the intracellular mechanism of retinal neuron maturation. Methods Whole cell patch clamp recordings of RGCs in acute retinal slices of Long Evans rats (postnatal days 3 to 31) were performed. Depolarizing current pulses of different densities were inflicted on RGCs to evoke action potentials(AP) . Results A total of 94 RGCs, single spike cells, transient and sustained cells, were acquired in 33 rats. The proportion of the three types of TGCs was different. There was significant difference in electrophysiological properties. Conclusion During the period of postnatal development, gradually matured electrophysiological properties of RGCs and differences in amplitudes and frequencies of AP suggest that different types of RGCs may play different roles in coding and transmitting spatial and temporal information.

EFFECT OF DA ON GABA-ACTIVATED CURRENT IN RAT DRG NEURONS / 神经解剖学杂志

Whole-cell patch-clamp technique was performed on isolated rat DRG neurons to investigate the modulation of DA onGABA-activated membrane currents. It was found that majority of the examined neurons(40/47) were sensitive to GABA, 10-6～ 103mol/L GABA activated a dose-dependent inward current which had an obvious desensitization. In 26 of 40 neurons sensitiveto GABA DA induced a little outward current which had no desentization at all. Others showed no effect obviously. When theneurons were treated with DA 10-7～10-4 mol/L prior to the application of GABA for 30 s, 68% (27/40) GABA-activated mem-brane currents were inhibited, whereas DA10-5 inhibited markedly(33.3%) (x±s).