Xia Luxi, Damon Tracey, Niblock Mary M, Bartlett Donald, Leiter J C
Dept. of Physiology, Dartmouth Medical School, Lebanon, NH 03756, USA.
J Appl Physiol (1985). 2007 Nov;103(5):1864-72. doi: 10.1152/japplphysiol.00524.2007. Epub 2007 Sep 6.
The laryngeal chemoreflex (LCR) is elicited by water in the larynx and leads to apnea and respiratory disruption in immature animals. The LCR is exaggerated by the elevation of brain temperature within or near the nucleus of the solitary tract (NTS) in decerebrate piglets. Thermal prolongation of reflex apnea elicited by superior laryngeal nerve stimulation is reduced by systemic administration of GABA(A) receptor antagonists. Therefore, we tested the hypothesis that microdialysis within or near the NTS of gabazine, a GABA(A) receptor antagonist, would reverse thermal prolongation of the LCR. We examined this hypothesis in 21 decerebrate piglets (age 3-13 days). We elicited the LCR by injecting 0.1 ml of water into the larynx before and after each piglet's body temperature was elevated by approximately 2.5 degrees C and before and after 2-5 mM gabazine was dialyzed unilaterally and focally in the medulla. Elevated body temperature failed to prolong the LCR in one piglet, which was excluded from analysis. Elevated body temperature prolonged the LCR in all the remaining animals, and dialysis of gabazine into the region near the NTS (n = 10) reversed the thermal prolongation of the LCR even though body temperature remained elevated. Dialysis of gabazine in other medullary sites (n = 10) did not reverse thermal prolongation of the LCR. Gabazine had no consistent effect on baseline respiratory activity during hyperthermia. These findings are consistent with the hypothesis that hyperthermia activates GABAergic mechanisms in or near the NTS that are necessary for the thermal prolongation of the LCR.
喉化学反射（LCR）由喉部的水引发，会导致未成熟动物出现呼吸暂停和呼吸紊乱。在去大脑的仔猪中，孤束核（NTS）内或其附近的脑温升高会使LCR增强。全身给予GABA(A)受体拮抗剂可减少由喉上神经刺激引起的反射性呼吸暂停的热延长。因此，我们检验了这样一个假设，即在NTS内或其附近微量透析GABA(A)受体拮抗剂加巴喷丁会逆转LCR的热延长。我们在21只去大脑的仔猪（年龄3 - 13天）中检验了这一假设。在每只仔猪体温大约升高2.5摄氏度前后，以及在延髓单侧局部透析2 - 5 mM加巴喷丁前后，我们通过向喉部注射0.1 ml水来引发LCR。有一只仔猪体温升高未能延长LCR，该仔猪被排除在分析之外。其余所有动物体温升高均延长了LCR，向NTS附近区域透析加巴喷丁（n = 10）可逆转LCR的热延长，尽管体温仍处于升高状态。在延髓其他部位透析加巴喷丁（n = 10）并未逆转LCR的热延长。加巴喷丁对热疗期间的基线呼吸活动没有一致影响。这些发现与以下假设一致，即热疗激活了NTS内或其附近对LCR热延长必需的GABA能机制。
