Se and neuropathic pain in the late-phase.Brain 2014: 137; 2193|Spinal cord astrocytes, connexin-43 and late-phase neuropathic painThe emerging literature strongly implicates a part for spinal cord glia, specially microglia and astrocytes inside the genesis and maintenance of neuropathic pain (Tsuda et al., 2005; Watkins and Maier, 2005; Gao and Ji, 2010b; Ren and Dubner, 2010; Chiang et al., 2012; Ji et al., 2013). Microglia and astrocytes play distinct roles in neuropathic pain induction and upkeep (Raghavendra et al., 2003; Shi et al., 2012). Compared to microglial activation, astroglial activation in neuropathic discomfort situations is extra persistent and plays a additional essential part in neuropathic pain maintenance (Raghavendra et al., 2003; Zhang and De Koninck, 2006; Shi et al., 2012; Ji et al., 2013), though microglia are also involved in neuropathic discomfort maintenance (Tsuda et al., 2003; Katsura et al., 2006; Clark et al., 2007; Ji and Suter, 2007; Kobayashi et al., 2008). Notably, behavioural tests for neuropathic discomfort upkeep had been mainly performed in the initial 2 weeks of nerve injury in prior studies (Jin et al., 2003; Tsuda et al., 2003, 2011; Clark et al., 2007; Kawasaki et al., 2008). To ascertain the exclusive function of microglia and astrocytes within the late-phase neuropathic pain, we examined CCI-induced mechanical allodynia, a cardinal function of chronic neuropathic discomfort, three weeks following nerve injury. As expected, astroglial toxin L–aminoadipate but not microglial inhibitor minocycline lowered this late-phase neuropathic discomfort (Supplementary Fig. 2A). Regularly, preceding research showed that delayed minocycline remedy only inhibited heat hyperalgesia but not mechanical allodynia (Mei et al., 2011; Vanelderen et al., 2013). Even though intrathecal p38 inhibitor SB203580 reduced mechanical allodynia on Day ten (Jin et al., 2003), it did not affect allodynia on Day 21 (Supplementary Fig. 2C and D). In contrast, spinal inhibition of JNK, induced in astrocytes immediately after nerve injury (Zhuang et al., 2006), was nevertheless efficient in minimizing the late-phase neuropathic pain (Supplementary Fig. 2B). These findings indicate that astrocytes and astrocytic signalling might be crucial for driving latephase neuropathic pain. In certain, we demonstrated that Cx43 can also be critically involved in late-phase neuropathic discomfort. Cx43 and Cx30 will be the principal connexins expressed by astrocytes and Cx43 is upregulated inside the spinal cord just after peripheral nerve injury (Wu et al., 2011; Yoon et al., 2013) and spinal cord injury (Chen et al., 2012). Inhibition of Cx43 was shown to protect ischaemia (Rami et al.Acacetin , 2001), attenuate inflammation, strengthen functional recovery following spinal cord injury (Chen et al.Cilgavimab , 2012; Huang et al.PMID:24324376 , 2012), and block the improvement of central neuropathic discomfort right after spinal cord injury (Chen et al., 2012). These reports are constant with accumulating evidence from various groups suggesting the Cx43 contributes to thedevelopment of neuropathic discomfort (Spataro et al., 2004; Ohara et al., 2008; Yoon et al., 2013). Notably, spinal cord injuryinduced central neuropathic pain was abolished in Cx43/Cx30 double knockout mice but not in Cx30 knockout mice (Chen et al., 2012). The present study showed that persistent upregulation of Cx43 in spinal cord astrocytes (43 weeks) is necessary for generating late-phase neuropathic pain (Fig 2). Along with CBX, an extensively applied but non-selective blocker of Cx43 (Spataro et al., 200.