Electrophysiological and neuroanatomical evidence of sexual dimorphism in aortic baroreceptor and vagal afferents in rat
Electrophysiological and neuroanatomical evidence of sexual dimorphism in aortic baroreceptor and vagal afferents in rat
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DOI：
10.1152/ajpregu.90401.2008
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发表时间：
2008-10-01
影响因子：
2.8
通讯作者：
Schild, John H.
中科院分区：
文献类型：
--
作者：
Li, Bai-Yan;Qiao, Guo-Fen;Schild, John H.
心血管功能自主控制中性别二态性的证据既令人信服又令人困惑。在健康和疾病人群中，神经循环血流动力学中与性别相关的差异过于复杂，不可能完全与性激素相关。作为确定其他生理机制的第一步，我们研究了大鼠中低阈值有髓鞘和高阈值无髓鞘主动脉压力感受器传入的相对表达是否存在性别偏差。这两种类型的传入纤维对心率和血压具有明显不同的反射作用，因此对压力反射动力学的潜在影响可能很大。我们的结果结合了荧光识别的主动脉压力感受器神经元 (ABN) 的膜片钳研究和主动脉压力感受器神经纤维的形态分析，表明女性表现出更大比例的有髓压力感受器纤维（占压力感受器纤维总数的 24.8% 与 18.7%，P < 0.01），并表达在年龄匹配的男性中很少发现的有髓 ABN 功能亚型（11% 与 2.3%，n = 107，P < 0.01）。有趣的是，这种神经元表型在女性迷走神经传入神经元的一般群体中更为普遍（17.7% vs. 3.8%，n = 169，P < 0.01），并且卵巢切除术不会改变其表达，但会降低神经元兴奋性。这些数据表明雌性和雄性大鼠的主动脉压力感受器传入之间存在基本的神经解剖学和电生理学差异。与男性相比，低阈值有髓鞘传入神经的如此广泛存在如何成为女性压力反射敏感性和迷走神经张力改变的一个促成因素，提出了可能的解释。
Evidence for sexual dimorphism in autonomic control of cardiovascular function is both compelling and confounding. Across healthy and disease populations sex-associated differences in neurocirculatory hemodynamics are far too complex to be entirely related to sex hormones. As an initial step toward identifying additional physiological mechanisms, we investigated whether there is a sex bias in the relative expression of low-threshold-myelinated and high-threshold-unmyelinated aortic baroreceptor afferents in rats. These two types of afferent fibers have markedly different reflexogenic effects upon heart rate and blood pressure and thus the potential impact upon baroreflex dynamics could be substantial. Our results, using a combination of a patch-clamp study of fluorescently identified aortic baroreceptor neurons (ABN) and morphometric analysis of aortic baroreceptor nerve fibers, demonstrate that females exhibit a greater percentage of myelinated baroreceptor fibers (24.8% vs. 18.7% of total baroreceptor fiber population, P < 0.01) and express a functional subtype of myelinated ABN rarely found in age-matched males (11% vs. 2.3%, n = 107, P < 0.01). Interestingly, this neuronal phenotype is more prevalent in the general population of female vagal afferent neurons (17.7% vs. 3.8%, n = 169, P < 0.01), and ovariectomy does not alter its expression but does lessen neuronal excitability. These data suggest there are fundamental neuroanatomical and electrophysiological differences between aortic baroreceptor afferents of female and male rats. Possible explanations are presented as to how such a greater prevalence of low-threshold myelinated afferents could be a contributing factor to the altered baroreflex sensitivity and vagal tone of females compared with males.