Feng H S, Lynn R B, Han J, Brooks F P
School of Medicine, University of Pennsylvania, Philadelphia 19104.
Am J Physiol. 1990 Aug;259(2 Pt 1):G321-6. doi: 10.1152/ajpgi.1990.259.2.G321.
We investigated the gastric acid secretory and motility responses to microinjection into the dorsal motor nucleus of the vagus (DMV) of RX 77368, a stable thyrotropin-releasing hormone (TRH) analogue, and bicuculline, a gamma-aminobutyric acid (GABAA) receptor antagonist in ketamine-chloralose-anesthetized cats. Gastric acid output was collected every 15 min through a gastric cannula after saline flush and titrated to pH 7.0. Antral contractions were continuously recorded by an extraluminal strain gauge force transducer. The chemicals were dissolved in saline and unilaterally microinjected in volumes of 200 nl. RX 77368 or bicuculline microinjected into the DMV induced significant dose-dependent (50-500 ng) increases in gastric acid secretion and significant dose-dependent (50-200 ng) increases in the force of antral contractions. In response to both chemicals the gastric acid output increased in the first 15 min and peaked in the second and third collections. RX 77368 (500 ng) had a second greater peak 90 min after microinjection. The motility responses were rapid in onset and lasted 60 min for RX 77368 and 30 min for bicuculline. The minimal effective dose for eliciting increased motility was consistently lower than inducing acid secretion. Electrical stimulation of the DMV with 100 microA, 50-Hz, and 0.2-ms pulse duration increased the force of antral contractions but had no effect on gastric acid secretion. Our results demonstrate that the DMV exerts important control over both gastric acid secretion and motility in cats. TRH exerts a stimulatory influence, while GABAA receptors mediate an inhibitory influence on this vagal control.
我们研究了在氯胺酮 - 氯醛糖麻醉的猫中，向迷走神经背运动核（DMV）微量注射稳定的促甲状腺激素释放激素（TRH）类似物RX 77368和γ-氨基丁酸（GABAA）受体拮抗剂荷包牡丹碱后，胃酸分泌和运动反应的变化。在生理盐水冲洗后，通过胃插管每15分钟收集一次胃酸分泌量，并滴定至pH 7.0。通过腔外应变片式力传感器连续记录胃窦收缩情况。将化学物质溶解于生理盐水中，以200 nl的体积进行单侧微量注射。向DMV微量注射RX 77368或荷包牡丹碱可引起胃酸分泌显著的剂量依赖性（50 - 500 ng）增加，以及胃窦收缩力显著的剂量依赖性（50 - 200 ng）增加。对这两种化学物质的反应，胃酸分泌量在最初15分钟内增加，并在第二次和第三次收集时达到峰值。RX 77368（500 ng）在微量注射后90分钟出现第二个更大的峰值。运动反应起效迅速，RX 77368持续60分钟，荷包牡丹碱持续30分钟。引起运动增加的最小有效剂量一直低于诱导胃酸分泌的剂量。用100 μA、50 Hz和0.2 ms脉冲持续时间的电刺激DMV可增加胃窦收缩力，但对胃酸分泌无影响。我们的结果表明，DMV对猫的胃酸分泌和运动均发挥重要的控制作用。TRH发挥刺激作用，而GABAA受体介导对这种迷走神经控制的抑制作用。
