Control of drinking behavior in eels neuronal circuit for swallowing reflex

颅内给药血管紧张素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提高了饮酒率。心房利钠肽、血管催产素（AVT）、缓动素、胃促生长素和苯肾上腺素对饮酒率的抑制呈剂量依赖性（Kozaka, Fujii & Ando, 2003）。静脉注射这些配体也观察到这些致病性或抗致病性作用（Ando等，2002年）。不同给药方式的相似效果表明这些配体对大脑起作用。然而，一般来说，大多数肽不能通过血脑屏障（BBB）。因此需要一些缺乏血脑屏障的特殊部位来解释上述结果。这种特殊的部位被称为哺乳动物的心室周围器官（CVOs）。通过腹腔注射Evans蓝（EB），荧光显微镜下检测EB阳性细胞核，寻找鳗鲡体内的CVOs。众所周知，EB与血清白蛋白结合，EB-白蛋白复合物不能通过血脑屏障。EB染色大细胞视前核（PM）、结节前核（ANT）和后脑区（AP）。PM对ANG II和AVT抗体有免疫反应，AP用抗酪氨酸羟化酶（TH）抗体染色（Mukuda, Matunaga & Ando，提交）。吞咽是由于食道上括约肌（UES）的松弛。当将EB注射到UES肌时，延髓内的舌咽部迷走神经运动复合体（GVC）被逆行标记，GVC对胆碱乙酰转移酶抗体产生免疫反应（Mukuda & Ando, 2003）。确实，UES肌是由胆碱能神经元支配的（Kozaka and Ando, 2003）。儿茶酚胺抑制GVC的神经元活性，AP的th免疫反应纤维投射到GVC （Mukuda & Ando, in preparation）。还构建了鳗鱼的脑图谱（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)