Baptista V, Zheng Z L, Coleman F H, Rogers R C, Travagli R A
Department of Neuroscience, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, 70808, USA.
J Neurophysiol. 2005 Oct;94(4):2763-71. doi: 10.1152/jn.00351.2005. Epub 2005 Aug 10.
Cholecystokinin (CCK) is released from enteroendocrine cells after ingestion of nutrients and induces multiple effects along the gastrointestinal tract, including gastric relaxation and short-term satiety. We used whole cell patch-clamp and immunohistochemical techniques in rat brain stem slices to characterize the effects of CCK. In 45% of the neurons of nucleus tractus solitarius subnucleus centralis (cNTS), perfusion with the sulfated form of CCK (CCK-8s) increased the frequency of spontaneous excitatory currents (sEPSCs) in a concentration-dependent manner (1-300 nM). The threshold for the CCK-8s excitatory effect was 1 nM, the EC(50) was 20 nM, and E(max) was 100 nM. The excitatory effects of CCK-8s were still present when the slices were preincubated with tetrodotoxin or bicuculline or when the recordings were conducted with Cs(+) electrodes. Pretreatment with the CCK-A receptor antagonist, lorglumide (1 microM), antagonized the effects of CCK-8s, whereas perfusion with the CCK-B preferring agonist CCK-8 nonsulfated (CCK-ns, 1 microM) did not affect the frequency of sEPSCs. Similarly, pretreatment with the CCK-B receptor antagonist, triglumide (1 microM), did not prevent the actions of CCK-8s. Although the majority (i.e., 76%) of CCK-8s unresponsive cNTS neurons had a bipolar somata shape and were TH-IR negative, no differences were found in either the morphological or the neurochemical phenotype of cNTS neurons responsive to CCK-8s. Our results suggest that the excitatory effects of CCK-8s on terminals impinging on a subpopulation of cNTS neurons are mediated by CCK-A receptors; these responsive neurons, however, do not have morphological or neurochemical characteristics that automatically distinguish them from nonresponsive neurons.
摄入营养物质后，肠内分泌细胞会释放胆囊收缩素（CCK），它会在胃肠道产生多种作用，包括胃舒张和短期饱腹感。我们运用全细胞膜片钳和免疫组化技术，在大鼠脑干切片中研究CCK的作用。在孤束核中央亚核（cNTS）45%的神经元中，灌注硫酸化形式的CCK（CCK-8s）会以浓度依赖方式（1-300 nM）增加自发兴奋性电流（sEPSCs）的频率。CCK-8s兴奋作用的阈值为1 nM，半数有效浓度（EC50）为20 nM，最大效应（E max）为100 nM。当切片用河豚毒素或荷包牡丹碱预孵育，或用Cs(+)电极进行记录时，CCK-8s的兴奋作用依然存在。用CCK-A受体拮抗剂洛谷胺（1 microM）预处理可拮抗CCK-8s的作用，而灌注CCK-B优先激动剂非硫酸化CCK-8（CCK-ns，1 microM）则不影响sEPSCs的频率。同样，用CCK-B受体拮抗剂曲谷胺（1 microM）预处理也不能阻止CCK-8s的作用。尽管大多数（即76%）对CCK-8s无反应的cNTS神经元具有双极胞体形态且酪氨酸羟化酶免疫反应阴性，但对CCK-8s有反应的cNTS神经元在形态或神经化学表型上均未发现差异。我们的结果表明，CCK-8s对投射到cNTS神经元亚群终末的兴奋作用是由CCK-A受体介导的；然而，这些有反应的神经元在形态或神经化学特征上并不能自动将它们与无反应的神经元区分开来。
