Abstract：
Swallowing is induced by a central pattern generator in the nucleus tractus solitarius (NTS). We aimed to create a medullary slice preparation to elucidate the neural architecture of the central pattern generator of swallowing (Sw-CPG) and record its neural activities. Experiments were conducted on 2-day-old Sprague-Dawley rats (n = 46). The brainstem-spinal cord was transected at the pontomedullary and cervicothoracic junctions; the medulla was sliced transversely at thicknesses of 600, 700, or 800 μm. The rostral end of the slice was 100 μm rostral to the vagus nerve. We recorded hypoglossal nerve activity and electrically stimulated the vagus nerve or microinjected bicuculline methiodide (BIC) into the NTS. The 800-μm slices generated both rhythmic respiratory activity and electrically elicited neural activity. The 700-μm slices generated only respiratory activity, while the 600-μm slices did not generate any neural activity. BIC microinjection into the NTS in 800-μm slices resulted in the typical activity that closely resembled the swallowing activity reported in other experiments. This swallowing-like activity consistently lengthened the respiratory interval. Despite complete inhibition of respiratory activity, weak swallowing-like activity was observed under bath application of a non-NMDA receptor antagonist. Contrastingly, bath application of NMDA receptor antagonists resulted in a complete loss of swallowing-like activity and no change in respiratory activity. These results suggest that the 800-μm medullary slice preparation contains both afferent and efferent neural circuits and pattern generators of swallowing activity. Additionally, NMDA receptors may be necessary for generating swallowing activity. This medullary slice preparation can therefore elucidate Sw-CPG neural networks.
摘要：
吞咽是由孤核（NTS）中的中央模式发生器引起的。我们旨在创建髓切片制剂，以阐明吞咽中央模式发生器（Sw-CPG）的神经结构并记录其神经活动。在2天大的Sprague-Dawley大鼠(n=46)上进行实验。在延髓和颈胸交界处横切脑干脊髓；将髓质横向切成600、700或800μm的厚度。切片的前端与迷走神经的前端为100μm。我们记录了舌下神经的活动，并电刺激了迷走神经或向NTS中微量注射了双瓜碱甲基碘（BIC）。800μm切片产生了有节奏的呼吸活动和电激发的神经活动。700μm切片仅产生呼吸活动，而600μm的切片没有产生任何神经活动。BIC显微注射到800μm切片的NTS中产生的典型活性与其他实验中报道的吞咽活性非常相似。这种类似吞咽的活动持续延长了呼吸间隔。尽管完全抑制了呼吸活动，在非NMDA受体拮抗剂浴中观察到弱的吞咽样活性。相反，NMDA受体拮抗剂的浴应用导致吞咽样活性的完全丧失和呼吸活性的变化。这些结果表明，800μm的髓质切片制剂包含传入和传出神经回路以及吞咽活动的模式发生器。此外,NMDA受体可能是产生吞咽活性所必需的。因此，这种髓质切片制备可以阐明Sw-CPG神经网络。
