Restoration of Estradiol Effects on Learning by Cholinergic Enhancement

描述（由申请人提供）：该项目的目标是提供雌二醇介导的认知功能增强的原理证明，通过使用胆碱酯酶抑制剂治疗，从而增强大脑中的胆碱能活性，可以恢复(a)有胆碱能病变的年轻大鼠，以及(b)长期卵巢功能丧失的老年大鼠。我们假设，绝经后雌二醇对认知能力产生积极影响的关键时期是由基底前脑胆碱能投射的功能决定的（即，当胆碱能系统明显受损时，反应性丧失）。基于此，我们预测从药理学上增强胆碱能系统（例如，通过使用胆碱酯酶抑制剂）将重新打开机会之窗并恢复反应性，即使在卵巢功能长期丧失之后。使用选择性免疫毒素192igg -皂苷（SAP）和我们实验室建立的方法，将在切除卵巢的年轻大鼠中隔和Broca斜带产生选择性的胆碱能神经元病变。这些大鼠将使用特定剂量的多奈哌齐或加兰他明（胆碱酯酶抑制剂，常用于治疗阿尔茨海默病），加或不加雌二醇治疗，然后使用体内微透析和行为训练进行研究。老龄大鼠在3月龄时切除卵巢，然后在12月龄时用多奈哌齐或加兰他明加或不加雌二醇治疗，也将进行评估。所有大鼠将接受两个认知任务的训练，一个是延迟匹配-位置（DMP） t -迷宫任务，一个是配置关联（CA）操作性条件反射任务。体内微透析将用于测量对海马中乙酰胆碱释放的影响。海马和额叶皮层的胆碱乙酰转移酶和乙酰胆碱酯酶活性水平也将作为胆碱能去神经支配程度的指标进行测量。我们的预测是，在有胆碱能损伤的大鼠和老年大鼠中，雌二醇的作用将通过胆碱酯酶抑制剂治疗而恢复，并且这些作用将与乙酰胆碱酯酶抑制和海马中乙酰胆碱释放相关。这将为增强大脑胆碱能活性可以恢复雌二醇增强基底前脑胆碱能功能受损的年轻大鼠和卵巢功能长期丧失的老年大鼠的认知能力提供原理证明。人类和动物的数据都表明，激素治疗的时间相对于更年期是决定治疗是否对大脑衰老和认知有有益影响的关键。我们假设，绝经后雌二醇对认知能力产生积极影响的关键时期是由基底前脑胆碱能投射的功能决定的（即，当胆碱能系统明显受损时，反应性丧失）。基于这一假设，我们预测从药理学上增强胆碱能系统（例如，通过使用胆碱酯酶抑制剂）将重新打开机会之窗，并恢复激素治疗对认知能力的有益影响(a)在胆碱能损伤的年轻大鼠中，(b)在经历了长期卵巢功能丧失的老年大鼠中。这一试点项目将为这一假设提供主要证据。积极的结果将确定一种机制来解释为什么绝经后激素治疗的时间是至关重要的，并将为多年未使用激素治疗的绝经后妇女恢复激素治疗的有效性提供一种可行的策略。

DESCRIPTION (provided by applicant): The goal of this project is to provide proof of principle that estradiol-mediated enhancement of cognitive function can be restored (a) in young rats with cholinergic lesions, and (b) in aged rats that have undergone long-term loss of ovarian function, by treating with a cholinesterase inhibitor and thereby enhancing cholinergic activity in the brain. We hypothesize that the critical period for eliciting positive effects of estradiol on cognitive performance post menopause is defined by the functionality of basal forebrain cholinergic projections (i.e., responsiveness is lost when the cholinergic system becomes significantly impaired). Based on this, we predict that enhancing the cholinergic system pharmacologically (e.g., via the use of cholinesterase inhibitors) will re-open the window of opportunity and restore responsiveness, even after prolonged loss of ovarian function. Selective lesions of cholinergic neurons in the medial septum and diagonal band of Broca will be produced in young ovariectomized rats using the selective immunotoxin 192IgG-saporin (SAP) and methods established in our laboratory. These rats will be treated with specific doses of donepezil or galantamine (cholinesterase inhibitors commonly used in the treatment of Alzheimer's disease), with and without estradiol, and then studied using in vivo microdialysis and behavioral training. Aged rats that are ovariectomized at 3 month of age, and then treated at 12 months of age with donepezil or galantamine with and without estradiol, will also be evaluated. All rats will be trained on two cognitive tasks, a delayed matching-to-position (DMP) T-maze task, and a configural association (CA) operant conditioning task. In vivo microdialysis will be used to measure effects on acetylcholine release in the hippocampus. Levels of choline acetyltransferase and acetylcholinesterase activities in the hippocampus and frontal cortex also will be measured as indices of the degree of cholinergic denervation. Our prediction is that in rats with cholinergic lesions, and in aged rats, effects of estradiol will be restored by treatment with the cholinesterase inhibitors, and that these effects will correlate with AChE inhibition and with acetylcholine release in the hippocampus. This would provide proof of principle that enhancing cholinergic activity in the brain can reinstate the ability of estradiol to enhance cognitive performance both in young rats with impaired basal forebrain cholinergic function, and in aged rats that have undergone long-term loss of ovarian function. PUBLIC HEALTH RELEVANCE Both human and animal data suggest that the timing of hormone therapy relative to menopause is critical for determining whether therapy will have a beneficial effect on brain aging and cognition. We hypothesize that the critical period for eliciting positive effects of estradiol on cognitive performance post menopause is defined by the functionality of basal forebrain cholinergic projections (i.e., responsiveness is lost when the cholinergic system becomes significantly impaired). Based on this hypothesis, we predict that enhancing the cholinergic system pharmacologically (e.g., via the use of a cholinesterase inhibitor) will re-open the window of opportunity and restore beneficial effects of hormone therapy on cognitive performance (a) in young rats with cholinergic lesions, and (b) in aged rats that have undergone long-term loss of ovarian function. This pilot project will provide proof of principal for this hypothesis. Positive results would identify a mechanism to explain why the timing of hormone therapy post menopause is critical, and would provide a viable strategy for restoring the effectiveness of hormone therapy in postmenopausal women who have not used hormone therapy for many years.