Spinal cannabinoid receptor 1 (CBR) and purinergic P2X receptors (P2XR) play a critical role in the process of pathological pain. Both CBR and P2XR are expressed in spinal dorsal horn (DH) neurons. It is not clear whether CB receptor activation modulates the function of P2X receptor channels within dorsal horn. For this reason, we observed the effect of CP55940 (cannabinoid receptor agonist) on ATP-induced Ca mobilization in cultured rat DH neurons. The changes of intracellular calcium concentration ([Ca]i) were detected with confocal laser scanning microscopy using fluo-4/AM as a calcium fluorescent indicator. 100 μM ATP caused [Ca]i increase in cultured DH neurons. ATP-evoked [Ca]i increase in DH neurons was blocked by chelating extracellular Ca and P2 purinoceptor antagonist PPADS. At the same time, ATP-γ-S (a non-hydrolyzable ATP analogue) mimicked the ATP action, while P2Y receptor agonist ADP failed to evoke [Ca]i increase in cultured DH neurons. These data suggest that ATP-induced [Ca]i elevation in cultured DH neurons is mediated by P2X receptor. Subsequently, we noticed that, in cultured rat DH neurons, ATP-induced Ca mobilization was inhibited after pretreated with CP55940 with a concentration-dependent manner, which implies that the opening of P2X receptor channels are down-regulated by activation of cannabinoid receptor. The inhibitory effect of CP55940 on ATP-induced Ca response was mimicked by ACEA (CBR agonist), but was not influenced by AM1241 (CBR agonist). Moreover, the inhibitory effect of CP55940 on ATP-induced Ca mobilization was blocked by AM251 (CB receptor antagonist), but was not influenced by AM630 (CB receptor antagonist). In addition, we also observed that forskolin (an activator of adenylate cyclase) and 8-Br-cAMP (a cell-permeable cAMP analog) reversed the inhibitory effect of CP55940, respectively. In a summary, our observations raise a possibility that CBR rather than CBR can downregulate the opening of P2X receptor channels in DH neurons. The reduction of cAMP/PKA signaling is a key element in the inhibitory effect of CBR on P2X-channel-induced Ca mobilization.
A transient numerical simulation method is used to investigate the temperature field, velocity field, and solidified field of large-size Waspaloy superalloy during the electroslag remelting (ESR) process. The effects of melting rate, filling rate, and thickness of the slag layer on the molten pool shape and dendrite arm spacing evolution have been discussed. The temperature in the slag pool is high and relatively uniformly distributed, the temperature range is 1690–1830 K. The highest temperature of the melt pool appears in the center of the slag–metal interface, 1686 K. There are two pairs of circulating vortices in the slag pool, the side vortices are caused by the density difference caused by the buoyancy of the slag, the center vortices are the result of the combined action of electromagnetic force and the momentum of the falling metal droplets. The molten pool depth and dendrite arm spacing increase with the increase of melting rate, but the slag layer thickness and electrode filling rate have little effect on the molten pool morphology and dendrite arm spacing if the droplet effect is not taken into account. Considering the morphology and depth of the molten pool as well as the size and distribution uniformity of the dendrite arm spacing, it is appropriate to maintain the melting rate at 5.8 kg/min for the industrial scale ESR process with the ingot diameter of 580 mm.
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