Abstract：
Neuropeptide cocaine- and amphetamine-regulated transcript peptide (CARTp) is known to play an important role in reward processing. The rats conditioned to intra-cranial self-stimulation (ICSS) showed massive upregulation of CART protein and mRNA in the vicinity of the electrode implanted to deliver the electric current directly at the lateral hypothalamus (LH)-medial forebrain bundle (MFB) area. However, the underlying mechanisms leading to the upregulation of CART in ICSS animals remain elusive. We tested the putative role of CREB-binding protein (CBP), an epigenetic enzyme with intrinsic histone acetyltransferase (HAT) activity, in regulating CART expression during ICSS. An electrode was implanted in LH-MFB and the rats were conditioned to self-stimulation in an operant chamber. CBP siRNA was delivered ipsilaterally in the LH-MFB to knock-down CBP and the effects on lever press activity were monitored. While ICSS-conditioned rats showed distinct increase in CART, CBP and pCREB levels, enhanced CBP binding and histone acetylation (H3K9ac) were noticed on the CART promoter in chromatin immunoprecipitation assay. Direct infusion of CBP siRNA in the LH-MFB lowered lever press activity, CBP levels, histone acetylation at the CART promoter, and CART mRNA and peptide expression. Co-infusion of CARTp in LH-MFB rescued the waning effects of CBP siRNA on self-stimulation. We suggest that CBP-mediated histone acetylation may play a causal role in CART expression in LH, which in turn may drive the positive reinforcement of lever press activity.
摘要：
已知神经肽可卡因和苯丙胺调节的转录肽（CARTp）在奖励处理中起重要作用。适应颅内自我刺激（ICSS）的大鼠在植入的电极附近显示CART蛋白和mRNA的大量上调，以直接在下丘脑外侧（LH）-内侧前脑束（MFB）区域传递电流。然而,导致ICSS动物CART上调的潜在机制仍然难以捉摸。我们测试了CREB结合蛋白(CBP)的推定作用，具有内在组蛋白乙酰转移酶（HAT）活性的表观遗传学酶，在ICSS期间调节CART表达。将电极植入LH-MFB中，并使大鼠在手术室中适应自我刺激。CBPsiRNA在LH-MFB中同侧递送以击倒CBP，并监测对杠杆按压活动的影响。虽然ICSS条件大鼠显示CART明显增加，CBP和pCREB水平,在染色质免疫沉淀分析中，在CART启动子上发现了增强的CBP结合和组蛋白乙酰化（H3K9ac）。在LH-MFB中直接输注CBPsiRNA降低了杠杆按压活动，CBP水平,CART启动子处的组蛋白乙酰化，和CARTmRNA和肽表达。在LH-MFB中共同输注CARTp挽救了CBPsiRNA对自我刺激的减弱作用。我们建议CBP介导的组蛋白乙酰化可能在LH的CART表达中起因果作用。这反过来可能会推动杠杆压力机活动的积极强化。
