Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania 17033-0850, USA.
Am J Physiol Regul Integr Comp Physiol. 2011 Aug;301(2):R394-401. doi: 10.1152/ajpregu.00054.2011. Epub 2011 May 4.
Baroreceptor inputs to nucleus of the tractus solitarius medialis (mNTS) neurons can be differentiated, among other features, by their response to vanilloid or purinergic agonists, active only on C- or A-fibers, respectively. A major aim of this study was to examine whether neurons of NTS centralis (cNTS), a subnucleus dominated by esophageal inputs, exhibit a similar dichotomy. Since it has been suggested that cholecystokinin (CCK), exerts its gastrointestinal (GI)-related effects via paracrine activation of vagal afferent C-fibers, we tested whether CCK-sensitive fibers impinging upon cNTS neurons are responsive to vanilloid but not purinergic agonists. Using whole cell patch-clamp recordings from cNTS, we recorded miniature excitatory postsynaptic currents (mEPSCs) to test the effects of the vanilloid agonist capsaicin, the purinergic agonist α,β-methylene-ATP (α,β-Met-ATP), and/or CCK-octapeptide (CCK-8s). α,β-Met-ATP, capsaicin; and CCK-8s increased EPSC frequency in 37, 71, and 46% of cNTS neurons, respectively. Approximately 30% of cNTS neurons were responsive to both CCK-8s and α,β-Met-ATP, to CCK-8s and capsaicin, or to α,β-Met-ATP and capsaicin, while 32% of neurons were responsive to all three agonists. All neurons responding to either α,β-Met-ATP or CCK-8s were also responsive to capsaicin. Perivagal capsaicin, which is supposed to induce a selective degeneration of C-fibers, decreased the number of cNTS neurons responding to capsaicin or CCK-8s but not those responding to α,β-Met-ATP. In summary, GI inputs to cNTS neurons cannot be distinguished on the basis of their selective responses to α,β-Met-ATP or capsaicin. Our data also indicate that CCK-8s increases glutamate release from purinergic and vanilloid responsive fibers impinging on cNTS neurons.
压力感受器传入到内侧孤束核神经元（mNTS）的信号可以通过其对香草酸或嘌呤能激动剂的反应来区分，这两种激动剂分别仅作用于 C 纤维或 A 纤维。本研究的主要目的是检验食管传入为主的神经中枢（cNTS）神经元是否也存在类似的二分法。由于胆囊收缩素（CCK）被认为通过迷走传入 C 纤维的旁分泌激活来发挥其胃肠道（GI）相关作用，我们测试了作用于 cNTS 神经元的 CCK 敏感纤维是否对香草酸激动剂有反应，但对嘌呤能激动剂无反应。通过对 cNTS 的全细胞膜片钳记录，我们记录了微小兴奋性突触后电流（mEPSC）以测试香草酸激动剂辣椒素、嘌呤能激动剂α,β-亚甲基-ATP（α,β-Met-ATP）和/或 CCK-八肽（CCK-8s）的作用。α,β-Met-ATP、辣椒素和 CCK-8s 分别使 cNTS 神经元的 EPSC 频率增加了 37%、71%和 46%。大约 30%的 cNTS 神经元对 CCK-8s 和 α,β-Met-ATP、CCK-8s 和辣椒素或 α,β-Met-ATP 和辣椒素有反应，而 32%的神经元对所有三种激动剂都有反应。对 α,β-Met-ATP 或 CCK-8s 中的任何一种有反应的神经元也对辣椒素有反应。颈旁注射辣椒素会导致 C 纤维选择性退化，这会减少对辣椒素或 CCK-8s 有反应的 cNTS 神经元的数量，但对 α,β-Met-ATP 有反应的神经元数量不变。总之，不能根据 cNTS 神经元对 α,β-Met-ATP 或辣椒素的选择性反应来区分它们的 GI 输入。我们的数据还表明，CCK-8s 增加了作用于 cNTS 神经元的嘌呤能和香草酸反应纤维的谷氨酸释放。
