Control of drinking behavior in eels neuronal circuit for swallowing reflex

颅内注射血管紧张素II(Ang II)、乙酰胆碱(Ach)、异丙肾上腺素和P物质以剂量依赖的方式增加饮酒率。心钠素、血管催产素(AVT)、缓激肽、Ghrelin和苯肾上腺素可剂量依赖性地抑制饮酒率(Kozaka，Fujii&Ando，2003)。静脉注射这些配体也观察到了这些生糖尿病或抗糖尿病的作用(Ando等人，2002年)。不同给药方法的相似效果表明，这些配体对大脑起作用。然而，一般情况下，大多数多肽都不能通过血脑屏障。因此，需要一些缺乏血脑屏障的特殊站点来解释上述结果。这种特殊的部位在哺乳动物中被称为脑室周围器官(CVO)。为了寻找鳗鱼体内的CVO，将伊文思蓝(EB)注射到鳗鱼体内，在荧光显微镜下观察EB阳性细胞核。众所周知，EB能与血清白蛋白结合，而EB-白蛋白复合体不能通过血脑屏障。用EB标记大细胞视前核(PM)、结节前核(ANT)和最后区(AP)。PM对抗Ang II和AVT的抗体呈免疫反应，AP用抗酪氨酸羟解酶(TH)抗体(Mukuda，Matunaga&Ando，提交)染色。吞咽是由于上食道括约肌(UES)肌肉松弛。当EB注入UES肌肉时，延髓中的舌咽迷走神经运动复合体(GVC)被逆行标记，并且GVC对胆碱乙酰转移酶抗体呈免疫反应(Mukuda&Ando，2003)。事实上，UES肌肉由胆碱能神经元支配(Kozaka和Ando，2003)。儿茶酚胺抑制GVC的神经元活动，AP的TH免疫反应纤维投射到GVC(Mukuda&Ando，准备中)。还建立了鳗鱼的脑图谱(Mukuda&Ando，2003)。

Intracranial administration of angiotensin II (ANG II), acetylcholine (Ach), isoproterenol, and substance P enhanced the drinking rate in a dose-dependent manner. Atrial natriuretic peptide, vasotocin (AVT), bradykinin, ghrelin, and phenylephrine inhibited the drinking rate dose-dependently (Kozaka, Fujii & Ando, 2003). These dipsogenic or antidipsogenic effects were also observed intravenous administration of these ligands (Ando et al., 2002). Similar effects by different administrations suggests that these ligands act on the brain. However, in general, most peptides can not pass through the blood-brain barrier (BBB). So some special sites which lack BBB are required to explain the above results. Such special sites are known as the circumventricular organs (CVOs) in mammals. To search for the CVOs in the eel, Evans blue (EB) was injected intraperitoneally and EB-positive nucleus was detected with fluorescent microscope. EB is well-known to bind serum albumin and the EB-albumin complex does not pass the BBB. The magnocellular preoptic nucleus (PM), anterior tuberal nucleus (ANT) and area postrema (AP) were stained with the EB. The PM was immunoreactive to the antibodies raised against ANG II and AVT, and the AP was stained with anti-tyrosine hydroxlase (TH) antibody (Mukuda, Matunaga & Ando, submitted). Swallowing is due to relaxation of the upper esophageal sphincter (UES) muscle. When EB was injected to the UES muscle, the glossopharyngeal vagal motor complex (GVC) in the medulla oblongate was labeled retrogradely and the GVC was immunoreactive to the antibody raised against choline acetyltransferase (Mukuda & Ando, 2003). Indeed, the UES muscle is innervated by cholinergic neurons (Kozaka and Ando, 2003). The neuronal activity of the GVC was inhibited by catecholamines, and the TH-immunoreactive fibers from the AP projected to the GVC (Mukuda & Ando, in preparation). Brain atlas of the eel was also constructed (Mukuda & Ando, 2003)