Neurotransmission evoked by 5HT-dependent luminal factor

描述(申请人提供)：先前的研究表明，迷走神经反射在调节餐后胰酶分泌中起着关键作用。在上一个资助阶段，我们证明了鲁米诺刺激诱导粘膜EC细胞释放5-羟色胺，进而激活迷走神经传入末梢上的5-羟色胺受体，刺激迷走神经初级感觉神经元；在这种方式下，5-羟色胺起旁分泌物质的作用，通过迷走神经胆碱能途径刺激胰腺分泌。本研究旨在研究结状神经节细胞至NTS神经元迷走神经传入通路的神经化学传递，以及DMN节前神经元至胰腺内神经元的迷走神经传出通路，从而介导腔内5-羟色胺依赖因子刺激的胰腺分泌。我们推测谷氨酸和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。多种神经递质在调节迷走神经向胰腺的传出信号中起关键作用：NPY和SP兴奋，生长抑素抑制DMN神经元。特定的DMN神经元群可能支配特定的胰腺内神经元，这些神经元含有不同的神经递质。为了验证这一假设，我们计划进行胰腺逆行追踪、c-Fos和神经递质免疫细胞化学，以表征迷走神经初级传入通路，以及由腔刺激激活的NTS和DMN神经元。电生理记录后标记结状神经节和NTS神经元将进一步证实参与传入NTS的神经递质和受体的传递。我们将记录迷走神经的放电，并确定刺激DMN激活的胰腺内神经节神经元的化学编码。最后，我们将使用清醒的大鼠模型来研究DMN中的各种神经递质在5-羟色胺依赖因子刺激的胰腺分泌中的中介作用。

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.