Ikegami Y, Maeda M, Yokota A, Hayashida Y
Department of Systems Physiology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu, Japan.
Brain Res. 1997 May 30;758(1-2):33-8. doi: 10.1016/s0006-8993(96)01428-x.
The extracellular lactate concentration and blood flow in the cerebral cortex of urethane-anesthetized, paralyzed and artificially ventilated rats were monitored continuously and simultaneously using an enzyme electrode and a laser Doppler flowmeter (LDF), respectively, during chemical stimulation of the nucleus tractus solitarii (NTS) by microinjection of L-glutamate (1.7 nmol 50 nl). Chemical stimulation of the NTS significantly decreased the arterial blood pressure (ABP) from 85 +/- 17 to 68 +/- 14 mmHg, heart rate from 418 +/- 13 to 402 +/- 19 beats x min(-1) and cerebral blood flow (CBF) by 17.9 +/- 6.2% (P < 0.001). However, chemical stimulation of the NTS significantly increased the lactate concentration by 58.9 +/- 17.3 microM (P < 0.001). Barostat maneuver, which held systemic ABP constant during chemical stimulation of the NTS attenuated the responses in CBF and lactate concentration by 30 and 27%, respectively. The onset of the increase in lactate concentration was delayed about 19 s after that of the CBF decrease. Circulatory lactate produced no significant change in the cerebral extracellular lactate concentration. These results indicate that chemical stimulation of the NTS induces an increase in extracellular lactate concentration in the cerebral cortex through a decrease in CBF via cerebral vasoconstriction.
在对氨基甲酸乙酯麻醉、瘫痪并人工通气的大鼠进行孤束核（NTS）化学刺激期间，分别使用酶电极和激光多普勒血流仪（LDF），连续同步监测大脑皮质的细胞外乳酸浓度和血流量。通过微量注射L-谷氨酸（1.7 nmol 50 nl）对NTS进行化学刺激。NTS的化学刺激使动脉血压（ABP）从85±17 mmHg显著降至68±14 mmHg，心率从418±13次/分钟降至402±19次/分钟，脑血流量（CBF）降低17.9±6.2%（P<0.001）。然而，NTS的化学刺激使乳酸浓度显著升高58.9±17.3 μM（P<0.001）。在对NTS进行化学刺激期间保持全身ABP恒定的压力调节操作分别使CBF和乳酸浓度的反应减弱30%和27%。乳酸浓度升高的起始时间比CBF降低的起始时间延迟约19秒。循环中的乳酸对大脑细胞外乳酸浓度没有显著影响。这些结果表明，NTS的化学刺激通过脑血管收缩导致CBF降低，从而引起大脑皮质细胞外乳酸浓度升高。
