McCord Jennifer L, Pellinger Thomas K, Lynn Brenna M, Halliwill John R
Department of Human Physiology, University of Oregon, Eugene, OR 97403, USA.
Med Sci Sports Exerc. 2008 Nov;40(11):1953-61. doi: 10.1249/MSS.0b013e31817f1970.
H1-receptors mediate the early portion (i.e., first 30 min after exercise) of postexercise hypotension. Immediately after exercise, syncope can occur due to an exaggerated form of postexercise hypotension. Therefore, we hypothesized that orthostatic hypotension occurring immediately after exercise would be attenuated with an H1-receptor antagonist.
We studied 15 endurance exercise-trained men and women in an environmental chamber set at 35 degrees C and 30.0% humidity. Subjects were studied in the supine position before a 45-min bout of treadmill running at 50% of VO2max. Immediately after exercise, measurements were taken in the supine position before the subjects were moved from a supine to a 60 degrees head-up tilt. Measurements included arterial pressure, heart rate, and brachial and cutaneous blood flow on a control and an H1-receptor antagonist (blockade) day.
Mean arterial pressure was reduced 1 min into the tilt compared with preexercise values on the control day (76.2 +/- 0.5 vs 74.2 +/- 0.5 mm Hg; P < 0.05). This reduction was not seen on the blockade day (75.2 +/- 0.3 vs 75.0 +/- 0.5 mm Hg; P > 0.41). There were no differences in brachial vascular conductance (calculated as flow/pressure) in response to the head-up tilt between the study days (P > 0.23). The length of the head-up tilt was compared between study days for each subject. When contrasting this difference, the blockade lengthened the mean tilt time by 94 s (P = 0.098).
These data suggest that an H1-receptor antagonist could potentially benefit postexercise syncope in a hot environment.
H1受体介导运动后低血压的早期阶段（即运动后最初30分钟）。运动后立即发生的晕厥可能是由于运动后低血压的一种夸张形式。因此，我们假设运动后立即出现的直立性低血压会因H1受体拮抗剂而减轻。
我们在温度设定为35摄氏度、湿度为30.0%的环境舱中研究了15名经过耐力运动训练的男性和女性。在以最大摄氧量的50%进行45分钟跑步机跑步之前，让受试者处于仰卧位进行研究。运动后立即在仰卧位进行测量，然后将受试者从仰卧位转为头向上倾斜60度。测量包括在对照日和H1受体拮抗剂（阻断）日的动脉压、心率以及肱动脉和皮肤血流量。
与对照日运动前的值相比，在倾斜1分钟时平均动脉压降低（76.2±0.5 vs 74.2±0.5毫米汞柱；P<0.05）。在阻断日未观察到这种降低（75.2±0.3 vs 75.0±0.5毫米汞柱；P>0.41）。在各研究日之间，对抬头倾斜的反应中肱血管传导率（计算为血流量/压力）没有差异（P>0.23）。比较了各研究日每个受试者的抬头倾斜时间。对比这种差异时，阻断使平均倾斜时间延长了94秒（P=0.098）。
这些数据表明，H1受体拮抗剂可能对热环境中的运动后晕厥有益。
