Abstract：
Cholinergic disruptions underlie attentional deficits following traumatic brain injury (TBI). Yet, drugs specifically targeting acetylcholinesterase (AChE) inhibition have yielded mixed outcomes. Therefore, we hypothesized that galantamine (GAL), a dual-action competitive AChE inhibitor and α7 nicotinic acetylcholine receptor (nAChR) positive allosteric modulator, provided chronically after injury, will attenuate TBI-induced deficits of sustained attention and enhance ACh efflux in the medial prefrontal cortex (mPFC), as assessed by in vivo microdialysis. In Experiment 1, adult male rats (n = 10-15/group) trained in the 3-choice serial reaction time (3-CSRT) test were randomly assigned to controlled cortical impact (CCI) or sham surgery and administered GAL (0.5, 2.0, or 5.0 mg/kg; i.p.) or saline vehicle (VEH; 1 mL/kg; i.p) beginning 24-h post-surgery and once daily thereafter for 27 days. Measures of sustained attention and distractibility were assessed on post-operative days 21-25 in the 3-CSRT, following which cortical lesion volume and basal forebrain cholinergic cells were quantified on day 27. In Experiment 2, adult male rats (n = 3-4/group) received a CCI and 24 h later administered (i.p.) one of the three doses of GAL or VEH for 21 days to quantify the dose-dependent effect of GAL on in vivo ACh efflux in the mPFC. Two weeks after the CCI, a guide cannula was implanted in the right mPFC. On post-surgery day 21, baseline and post-injection dialysate samples were collected in a temporally matched manner with the cohort undergoing behavior. ACh levels were analyzed using reverse phase high-performance liquid chromatography (HPLC) coupled to an electrochemical detector. Cortical lesion volume was quantified on day 22. The data were subjected to ANOVA, with repeated measures where appropriate, followed by Newman-Keuls post hoc analyses. All TBI groups displayed impaired sustained attention versus the pooled SHAM controls (p\'s < 0.05). Moreover, the highest dose of GAL (5.0 mg/kg) exacerbated attentional deficits relative to VEH and the two lower doses of GAL (p\'s < 0.05). TBI significantly reduced cholinergic cells in the right basal forebrain, regardless of treatment condition, versus SHAM (p < 0.05). In vivo microdialysis revealed no differences in basal ACh in the mPFC; however, GAL (5.0 mg/kg) significantly increased ACh efflux 30 min following injection compared to the VEH and the other GAL (0.5 and 2.0 mg/kg) treated groups (p\'s < 0.05). In both experiments, there were no differences in cortical lesion volume across treatment groups (p\'s > 0.05). In summary, albeit the higher dose of GAL increased ACh release, it did not improve measures of sustained attention or histopathological markers, thereby partially supporting the hypothesis and providing the impetus for further investigations into alternative cholinergic pharmacotherapies such as nAChR positive allosteric modulators.
摘要：
胆碱能破坏是创伤性脑损伤（TBI）后注意力缺陷的基础。然而，特异性靶向乙酰胆碱酯酶(AChE)抑制的药物产生了混合的结果.因此,我们假设加兰他敏(GAL)，一种双作用竞争性AChE抑制剂和α7烟碱乙酰胆碱受体（nAChR）正变构调节剂，在受伤后长期提供，将减轻TBI引起的持续注意力缺陷，并增强内侧前额叶皮层（mPFC）的ACh外排，通过体内微透析评估。在实验1中，将接受3选择系列反应时间（3-CSRT）测试训练的成年雄性大鼠（n=10-15/组）随机分配到受控皮质冲击（CCI）或假手术中，并在手术后24小时开始给予GAL（0.5、2.0或5.0mg/kg；i.p.）或盐水媒介物（VEH；1mL/kg；i.p），每天一次，持续27天。在3-CSRT中，在术后第21-25天评估了持续注意力和注意力分散的措施，随后在第27天对皮质病变体积和基底前脑胆碱能细胞进行定量。在实验2中，成年雄性大鼠（n=3-4/组）接受CCI，并在24小时后给予（i.p.）三种剂量的GAL或VEH之一，持续21天，以量化GAL对mPFC中体内ACh外排的剂量依赖性作用。CCI两周后,在右mPFC中植入引导套管。在手术后第21天,以与经历行为的组群时间匹配的方式收集基线和注射后透析液样品。使用与电化学检测器偶联的反相高效液相色谱(HPLC)分析ACh水平。在第22天定量皮质病变体积。数据进行了方差分析，在适当的情况下反复采取措施，其次是纽曼-基尔斯的事后分析。与合并SHAM对照相比，所有TBI组表现出持续注意力受损(p<0.05)。此外，相对于VEH和两种较低剂量的GAL,最高剂量的GAL(5.0mg/kg)加重了注意力缺陷(p<0.05)。TBI显著减少右基底前脑的胆碱能细胞，无论治疗条件如何，与SHAM（p<0.05）。体内微透析显示mPFC中基础ACh没有差异；然而，与VEH和其他GAL(0.5和2.0mg/kg)治疗组相比,GAL(5.0mg/kg)在注射后30分钟显著增加ACh外排(p<0.05)。在这两个实验中,各治疗组的皮质病变体积无差异(p>0.05)。总之,尽管较高剂量的GAL增加了ACh释放，它没有改善持续关注或组织病理学标志物的措施，从而部分支持该假设，并为进一步研究胆碱能药物治疗如nAChR正变构调节剂提供动力。
