Foley C M, McAllister R M, Hasser E M
Department of Veterinary Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri at Columbia, Columbia, Missouri 65211, USA.
Am J Physiol Heart Circ Physiol. 2001 May;280(5):H2061-8. doi: 10.1152/ajpheart.2001.280.5.H2061.
The effect of thyroid status on arterial baroreflex function and autonomic contributions to resting blood pressure and heart rate (HR) were evaluated in conscious rats. Rats were rendered hyperthyroid (Hyper) or hypothyroid (Hypo) with triiodothyronine and propylthiouracil treatments, respectively. Euthyroid (Eut), Hyper, and Hypo rats were chronically instrumented to measure mean arterial pressure (MAP), HR, and lumbar sympathetic nerve activity (LSNA). Baroreflex function was evaluated with the use of a logistic function that relates LSNA or HR to MAP during infusion of phenylephrine and sodium nitroprusside. Contributions of the autonomic nervous system to resting MAP and HR were assessed by blocking autonomic outflow with trimethaphan. In Hypo rats, the arterial baroreflex curve for both LSNA and HR was shifted downward. Hypo animals exhibited blunted sympathoexcitatory and tachycardic responses to decreases in MAP. Furthermore, the data suggest that in Hypo rats, the sympathetic influence on HR was predominant and the autonomic contribution to resting MAP was greater than in Eut rats. In Hyper rats, arterial baroreflex function generally was similar to that in Eut rats. The autonomic contribution to resting MAP was not different between Hyper and Eut rats, but predominant parasympathetic influence on HR was exhibited in Hyper rats. The results demonstrate baroreflex control of LSNA and HR is attenuated in Hypo but not Hyper rats. Thyroid status alters the balance of sympathetic to parasympathetic tone in the heart, and the Hypo state increases the autonomic contributions to resting blood pressure.
在清醒大鼠中评估甲状腺状态对动脉压力反射功能以及自主神经系统对静息血压和心率（HR）的影响。分别用三碘甲状腺原氨酸和丙硫氧嘧啶处理使大鼠变为甲状腺功能亢进（Hyper）或甲状腺功能减退（Hypo）。对甲状腺功能正常（Eut）、Hyper和Hypo大鼠进行长期仪器植入以测量平均动脉压（MAP）、HR和腰交感神经活动（LSNA）。在静脉注射去氧肾上腺素和硝普钠期间，使用将LSNA或HR与MAP相关联的逻辑函数评估压力反射功能。通过用三甲噻芬阻断自主神经传出通路来评估自主神经系统对静息MAP和HR的作用。在Hypo大鼠中，LSNA和HR的动脉压力反射曲线均向下移位。Hypo动物对MAP降低表现出减弱的交感兴奋和心动过速反应。此外，数据表明，在Hypo大鼠中，交感神经对HR的影响占主导，并且自主神经系统对静息MAP的作用大于Eut大鼠。在Hyper大鼠中，动脉压力反射功能通常与Eut大鼠相似。Hyper大鼠和Eut大鼠之间自主神经系统对静息MAP的作用没有差异，但Hyper大鼠表现出对HR的主要副交感神经影响。结果表明，Hypo大鼠中LSNA和HR的压力反射控制减弱，而Hyper大鼠中未减弱。甲状腺状态改变了心脏中交感神经与副交感神经张力的平衡，并且Hypo状态增加了自主神经系统对静息血压的作用。
