Neurotransmission evoked by 5HT-dependent luminal factor

描述（申请人提供）：以往的研究表明迷走反射在介导餐后胰酶分泌中起关键作用。在上一个资助期内，我们证明了腔内刺激诱导粘膜EC细胞释放5-HT，这反过来激活粘膜迷走神经传入末端的5-HT3受体，以刺激迷走神经初级感觉神经元；通过这种方式，5-羟色胺作为旁分泌物质通过迷走神经胆碱能途径刺激胰腺分泌。本研究旨在描述结节神经节神经元到NTS神经元的迷走神经传入通路和DMN神经节前神经元到胰腺内神经元的迷走神经传出通路中的神经化学传递，这些神经化学传递介导管腔5- ht依赖因子刺激胰腺分泌。我们假设谷氨酸和P物质是迷走神经初级传入神经元向NTS传递传入信息的主要神经递质。多种神经递质在DMN激发的活动整合在调节迷走神经输出信号到胰腺中起关键作用：NPY和SP刺激DMN神经元，而生长抑素抑制DMN神经元。特定的DMN神经元群可以支配含有不同神经递质的特定胰腺内神经元。为了验证这一假设，我们计划进行胰腺逆行示踪、c-Fos和神经递质免疫细胞化学来表征迷走神经初级传入通路，以及被管径刺激激活的NTS和DMN神经元。电生理记录以及结节神经节和NTS神经元的标记将进一步确认神经递质和受体参与传入输入到NTS的传递。我们将记录迷走胰腺神经的放电，并确定DMN刺激激活的胰腺内神经节神经元的化学编码。最后，我们将在有意识大鼠模型中研究DMN中各种神经递质在介导由管腔5ht依赖因子刺激的胰腺分泌中的作用。

DESCRIPTION (provided by applicant): Previous studies demonstrated that vago-vagal reflex plays a crucial role in the mediation of postprandial pancreatic enzyme secretion. During the last funding period, we demonstrated that luminal stimuli induced the release of 5-HT from mucosal EC cells, which in turn activated 5-HT3 receptors on mucosal vagal afferent terminals to stimulate vagal primary sensory neurons; in this manner, 5-HT acts as a paracrine substance to stimulate pancreatic secretion via a vagal cholinergic pathway. The current proposal is designed to characterize the neurochemical transmission in the vagal afferent pathway of nodose ganglia neurons to NTS neurons, and the vagal efferent pathway of DMN preganglionic neurons to intrapancreatic neurons, which mediate pancreatic secretion stimulated by luminal 5-HT-dependent factors. We hypothesize that glutamate and substance P are the major neurotransmitters responsible for transmitting afferent information from vagal primary afferent neurons to the NTS. The integration of activities excited by multiple neurotransmitters at the DMN plays a critical role in modulating the vagal efferent signaling to the pancreas: NPY and SP stimulate, while somatostatin inhibits DMN neurons. Specific groups of DMN neurons may innervate specific intrapancreatic neurons, which contain different neurotransmitters. To test this hypothesis we plan to perform pancreatic retrograde tracing, c-Fos, and neurotransmitters immunocytochemistry to characterize the vagal primary afferent pathway, as well as the NTS and DMN neurons, which are activated by luminal stimulation. Electrophysiological recording followed by labeling of nodose ganglia and NTS neurons will further confirm the neurotransmitters and receptors involved in the transmission of afferent inputs to the NTS. We will record the firing of the vagal pancreatic nerves and identify the chemical codings of the intrapancreatic ganglia neurons activated by DMN stimulation. Finally, we will examine the roles of various neurotransmitters in the DMN in the mediation of pancreatic secretion stimulated by luminal 5HT-dependent factors using a conscious rat model.