N-methyl-D-aspartic acid receptor/MAPK/cAMP-response element binding protein pathway mediating pain-related aversion in anterior cingulate cortex / 解剖学报

Objective To explore the mechanism of N-methyl-D-aspartic acid ( NMDA) receptor/MAPK/cAMPresponse element binding protein ( CREB) pathway involved in pain-related aversion mediated by anterior cingulate cortex. Methods A total of 42 healtlry SD rats were randomly divided into control group (Ctrl) , normal saline(NS) injection group (NS) , complete freund adjuvant (CFA) model group ( CFA ) , injected CFA into the soles of the foot and injected NS into rostral part of anterior cingulate cortex (rACC)group (CFA+NS) , injected NS into the soles of the foot and injected NS into rACC group (NS+NS) , injected CFA into the soles of the foot and injected NMDA receptor antagonist ( APV ) into rACC group (CFA+APV) , injected NS into the soles of the foot and injected APV into rACC group ( NS + APV ) with 6 rats in each group. Rats avoidance score was analysised and rat thermal foot contraction latency ( PWL) ws alserved, the expression of NMDA receptor in rACC region was detected by immunohistochemical staining, the expression of NMDA receptor, phosphorylated ERK( p-ERK) and phosphorylated CREB ( p - CREB ) in rACC region was detected by immunofluorescent staining, the number of Nissl bodies in rACC region was observed by Nissl staining, and the expression of NMDA receptor, MAPK, CREB, ERK, p-ERK, p-CREB, synaptosomal-associated protein 25 interaction protein 30 (SIP30) protein in rACCregion was detected by Western blotting, and Real-time PCR was used to detect the mRNA expression of NMDA receptor, MAPK, CREB and ERK in the rACC region. Results Compared with the Ctrl group, the avoidance score and PWL decreased significantly and the expression of NMDA receptor, MAPK and CREB increased significantly in the CFA group (P<0. 05). Compared with the CFA+NS group, the number of Nissl bodies in CFA+APV and NS+APV groups increased significantly, while the expression of NMDA receptor, MAPK, CREB, p-ERK and p-CREB decreased significantly in NS+NS and NS+APV groups (P<0. 05). Conclusion NMDA receptor-MAPK-CREB signal pathway in rACC is involved in painrelated aversion, and inhibition of NMDA can reduce pain-related negative aversion.

The BDNF-TrkB signaling pathway in the rostral anterior cingulate cortex is involved in the development of pain aversion in rats with bone cancer via NR2B and ERK-CREB signaling.

Patients with bone cancer pain (BCP) are more prone to aversion. which not only causes mental distress but also aggravates BCP. However, the mechanism of BCP-related aversion is still unclear. Previous studies have demonstrated that the brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling pathway of the rostral anterior cingulate cortex (rACC) plays an important role in the regulation of emotions related to chronic pain, such as neuropathic pain or inflammatory pain; however, few studies have investigated the role of this pathway in cancer pain. This study explored the role of BDNF in cancer pain-related aversion in the rACC and to determine whether N-methyl D-aspartate receptor subtype 2B (NR2B) and extracellular signal-regulated kinase (ERK)-cAMP response element-binding (CREB) signaling are involved in cancer pain-related aversion. A Sprague-Dawley rat model of BCP (one of the classic BCP models) was established, and the changes in pain aversion were detected by mechanical stimulation-induced conditioned place avoidance. Our findings confirmed that rats with BCP exhibited intense pain aversion accompanied by the up-regulated BDNF expression in the rACC. Additionally, the pain aversion of BCP rats was reduced while blocking the BDNF-TrkB. Furthermore, the expression of NR2B and phosphorylated ERK (pERK)/phosphorylated CREB (pCREB) were up-regulated with the development of pain aversion, whereas the use of NR2B blocker Ro25-6981, or ERK inhibitor U0126 could reduce the pain aversion. The expression of NR2B and pERK/pCREB were up-regulated after exogenous BDNF was injected into the rACC, whereas the expression levels of NR2B and pERK/pCREB were down-regulated after blocking the BDNF-TrkB signaling. In conclusion, the BDNF-TrkB signaling in the rACC mediates the generation of aversion in rats with BCP, which requires the involvement of NR2B and the ERK-CREB signaling pathway.

BDNF Activates mTOR to Upregulate NR2B Expression in the Rostral Anterior Cingulate Cortex Required for Inflammatory Pain-Related Aversion in Rats.

The mechanistic target of rapamycin (mTOR) has been demonstrated to mediate pain-related aversion induced by formalin in the rostral anterior cingulate cortex (rACC). However, it remains unclear the signaling pathways and regulatory proteins involved. In the rACC, brain-derived neurotrophic factor (BDNF), an activity-dependent neuromodulator, has been shown to play a role in the development and persistence of chronic pain. In this study, we used a rat formalin-induced inflammatory pain model to demonstrate BDNF up-regulation in the rACC. Stimulation with exogenous BDNF up-regulated mTOR, whilst cyclotraxin B (CTX-B), a tropomyosin receptor kinase B (TrkB) antagonist, down-regulated mTOR. Our results suggest BDNF could activate an mTOR signaling pathway. Subsequently, we used formalin-induced conditioned place avoidance (F-CPA) training in rat models to investigate if mTOR activation was required for pain-related aversion. We demonstrated that BDNF/mTOR signaling could activate the NMDA receptor subunit episilon-2 (NR2B), which is required for F-CPA. Our results reveal that BDNF activates mTOR to up-regulate NR2B expression, which is required for inflammatory pain-related aversion in the rACC of rats.

Contribution of BDNF/TrkB signalling in the rACC to the development of pain-related aversion via activation of ERK in rats with spared nerve injury.

The rostral anterior cingulate cortex (rACC) is a key structure in mediating the negative affective component of chronic pain. Brain-derived neurotrophic factor (BDNF) is known to play a critical role in activity-dependent synaptic plasticity, learning and memory. It has been shown that BDNF signalling in the rACC might be involved in spontaneous pain-related aversion, but its underlying mechanism is still largely unknown. To address this question, we measured the mRNA and protein levels of BDNF in the rACC after nerve injury and found that BDNF expression was markedly higher in nerve-injured rats than in controls. Moreover, we found that conditioned place avoidance (CPA), a behavioural phenotype reflecting pain-related aversion, was acquired in rats with partial sciatic nerve transection. However, a local injection of a BDNF-tropomyosin receptor kinase B (TrkB) antagonist into the rACC completely suppressed this process. Importantly, we found that administration of exogenous BDNF into the rACC of intact rats was sufficient to produce CPA, while selectively blocking phosphorylated extracellular signal regulated kinase (p-ERK) with a mitogen-activated protein kinase (MAPK) inhibitor U0126 completely abolished the acquisition of BDNF-induced CPA. In conclusion, we demonstrate, for the first time, that ERK is an important downstream effector of the BDNF/TrkB-mediated signalling pathway in the rACC that contributes to the development of neuropathic pain-related aversion.

Brain-derived neurotrophic factor (BDNF) in the rostral anterior cingulate cortex (rACC) contributes to neuropathic spontaneous pain-related aversion via NR2B receptors.

The rostral anterior cingulate cortex (rACC) plays an important role in pain affect. Previous investigations have reported that the rACC mediates the negative affective component of inflammatory pain and contributed to the aversive state of nerve injury-induced neuropathic pain. Brain-derived neurotrophic factor (BDNF), an activity-dependent neuromodulator in the adult brain, is believed to play a role in the development and maintenance of inflammatory and neuropathic pain in the spinal cord. However, whether and how BDNF in the rACC regulates pain-related aversion due to peripheral nerve injury is largely unknown. Behaviorally, using conditioned place preference (CPP) training in rats, which is thought to reveal spontaneous pain-related aversion, we found that CPP was acquired following spinal clonidine in rats with partial sciatic nerve transection. Importantly, BDNF was upregulated within the rACC in of rats with nerve injury and enhanced the CPP acquisition, while a local injection of a BDNF-tropomyosin receptor kinase B (TrkB) antagonist into the rACC completely blocked this process. Finally, we demonstrated that the BDNF/TrkB pathway exerted its function by activating the NR2B receptor, which is widely accepted to be a crucial factor contributing to pain affect. In conclusion, our results demonstrate that the BDNF/TrkB-mediated signaling pathway in the rACC is involved in the development of neuropathic spontaneous pain-related aversion and that this process is dependent upon activation of NR2B receptors. These findings suggest that suppression of the BDNF-related signaling pathway in the rACC may provide a novel strategy to overcome pain-related aversion.

Inhibition of mammalian target of rapamycin activation in the rostral anterior cingulate cortex attenuates pain-related aversion in rats.

Pain is a complex experience that comprises both sensory and affective dimensions. Mammalian target of rapamycin (mTOR) plays an important role in the modulation of neuronal plasticity associated with the pathogenesis of pain sensation. However, the role of mTOR in pain affect is unclear. Using a formalin-induced conditioned place avoidance (F-CPA) test, the current study investigated the effects of the mTOR specific inhibitor rapamycin on noxious stimulation induced aversion in the rostral anterior cingulate cortex (rACC). Intraplantar injection of 5% formalin was associated with significant activation of mTOR, as well as p70 ribosomal S6 protein (p70S6K), its downstream effector, in the rACC. The inhibition of mTOR activation with rapamycin disrupted pain-related aversion; however, this inhibition did not affect formalin-induced spontaneous nociceptive behaviors in rats. These findings demonstrated for the first time that mTOR and its downstream pathway in the rACC contribute to the induction of pain-related negative emotion.

Bone cancer pain induce anxiety-like behavior and high expression of NR2B subunit in anterior cingulate cortex of rats / 临床麻醉学杂志

Objective To investigate the effect of bone cancer pain on emotion and NMDA re-ceptor NR2B subunit expression level in anterior cingulate cortex (ACC)in rats.Methods One hun-dred and fifty healthy male Wistar rats weighing 200-250 g aged 3 months old were randomly divided into 3 groups (n = 50 in each group):sham operation group (group S),bone cancer pain group (group BCP),RO25-6981 group (group RO).The BCP model was established by inoculating Walker 256 breast cancer cells into right intra-tibial.Rats in group S were given the same dose of d-hanks. Group RO was injected intraperitoneally with RO25-6981 (5 mg/kg/d)on the day of inoculation, while rats in the group S and group BCP were given the same dose of normal saline.Mechanical with-drawal threshold (MWT)and thermal withdrawal latency (TWL)of right hind legs were measured on day 7,10,14 after inoculation respectively.Elevated plus-maze test was carried out to investigate the effect of bone cancer pain on emotion in rats after pain threshold detection,then the percentage of the times entering the open arms (OE)and the percentage of the time staying in the open arms (OT) duration the total period were evaluated.Then the anterior cingulate cortex tissue was removed to e-valuate the NR2B protein and mRNA expression levels by RT-PCR,Western blot and immunofluo-rescence methods on day 14 after elevated plus-maze test.Results All the parameters did not differ with significant difference between group S and group RO.MWT decreased and TWL shortened on day 7,10,14 after inoculation in group BCP compared with those before inoculation and those of group S and group RO.OE and OT in group BCP reduced remarkably than those before inoculation and those of group S and group RO.Relative absorbance of NR2B mRNA,the expression of NR2B pro-tein,average NR2B relative fluorescence intensity value is obviously higher than that of group S and group RO (P <0.05).Conclusion Bone cancer pain can induce pain-related aversion and anxiety-like behavior of rats,and the mechanism may be related to the high expression of NR2B in anterior cingu-late cortex.

Estrogen in the anterior cingulate cortex contributes to pain-related aversion.

The rostral anterior cingulate cortex (rACC) is a key structure of pain affect. Whether and how estrogen in the rACC regulates pain-related negative emotion remains unclear. Behaviorally, using formalin-induced conditioned place aversion (F-CPA) in rats, which is believed to reflect the pain-related negative emotion, we found that estrogen receptor (ER) inhibitor ICI 182, 780 (ICI, 7α,17ß-[9-[(4,4,5,5,5-Pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol) or inhibitor of aromatase androstatrienedione into the rACC completely blocked F-CPA in either sex. An analogous effect was also observed in ovariectomy rats. Furthermore, exogenous estrogen in the absence of a formalin noxious stimulus was sufficient to elicit CPA (E-CPA) in both sexes by activating the membrane estrogen receptors (mERs) and N-methyl-D-aspartic acid (NMDA) receptors (NMDARs). Electrophysiologically, we demonstrated that estrogen acutely enhanced the glutamatergic excitatory postsynaptic currents (EPSCs) in rACC slices by increasing the ratio of NMDA-EPSCs to α-amino-3-(5-methyl-3-oxo-1,2- oxazol-4-yl) propanoic acid -EPSCs and presynaptic glutamate release. Interestingly, a brief exposure to estrogen elicited a persistent enhancement of NMDA-EPSCs, and this NMDA-long-term potentiation required the activation of the mERs, protein kinase A and NMDAR subunit NR2B. Finally, estrogen induced rapid dendritic spine formation in cultured rACC neurons. These results suggest that estrogen in the rACC, as a neuromodulator, drives affective pain via facilitating NMDA receptor-mediated synaptic transmission.