Neural circuit regulating drinking behavior in the eel acclimated to sea water

虽然鳗鱼的心室周围器官（CVOs）尚未被鉴定，但我们在鳗鱼中鉴定了3个CVOs，即大细胞视前核（PM）、结节前核（NAT）和后脑区（AP）。PM和AP分别对抗缩素（AVT）抗体和酪氨酸羟化酶（TH）抗体产生免疫反应（Mukuda et al., 2005）。吞咽是由于食道上括约肌（UES）的松弛。在UES内注射Evans蓝后，逆行标记舌咽部-迷走神经运动复合体（GVC），这些神经元对胆碱乙酰转移酶抗体有免疫反应（Mukuda & Ando, 2003）。实际上，UES肌（横条肌）是由胆碱能神经元支配，并由乙酰胆碱能神经元收缩（Kozaka & Ando, 2003）。迷走神经在鳃弧后分为10支（X1-X10）。在这些迷走神经分支中，只有位于颈内静脉的X5神经支配UES，最佳频率为20 Hz （Ogawa & Ando, in preparation）。最佳频率的存在似乎是由于肌浆网上的Ca^<2+>- atp酶（Tamura & Ando, in preparation）。另一方面，通过AVT收缩UES，并通过cAMP用异肽素放松UES （Watanabe & Ando, in preparation）。儿茶酚胺对GVC神经元活性的抑制呈剂量依赖性，育亨宾阻断了这种抑制作用。由于迷走神经叶（LX）、Cajal联合核（NCC）、网状结构（RF）和髓质的AP对th抗体有免疫反应，其中一些核可能支配GVC （Ito, Mukuda & Ando，提交）。事实上，电刺激LX可以抑制GVC活性，但育亨宾并没有阻断这种抑制作用（Ito & Ando, in preparation）。因此，GVC的活动可能受到多种输入的调节，GVC上的神经元回路似乎很复杂。

Although the circumventricular organs(CVOs) in the eel is not identified yet, we identified 3 CVOs in the eel, magnocellular preoptic nucleus (PM), anterior tuberal nucleus (NAT) and area postrema (AP). The PM and the AP were immuno- reactive to vaosotocin (AVT)- and tyrosine hydroxylase (TH)-antibody, respectively (Mukuda et al., 2005).Swallowing is due to relaxation of the upper esophageal sphincter(UES) muscle. After injection of Evans blue into the UES, the glossopharyngeal-vagal motor complex (GVC) was labeled retrogradely, and these neurons were immunoreactive to choline acetyltransfetase-antibody (Mukuda & Ando, 2003). Indeed, the UES muscle (striated muscle) was innervated by a cholinergic neuron and constricted by ACh (Kozaka & Ando, 2003). The vagus nerve was divided to 10 branches (X1-X10) behind the gill arcs. Among these vagal branches, only X5 situated on the internal jugular vain innervated the UES, with optimal frequency of 20 Hz (Ogawa & Ando, in preparation). The existence of optimum frequency seems to be due to Ca^<2+>-ATPase on the sarcoplasmic reticulum (Tamura & Ando, in preparation). On the other hand, the UES was constricted by AVT and relaxed by isotocin via cAMP (Watanabe & Ando, in preparation).Neuronal activity of the GVC was inhibited by catecholamines in a dose-dependent manner, and this inhibitory effects were blocked by yohimbine. Since the vagal lobe (LX), the commissural nucleus of Cajal (NCC), the reticular formation (RF) and the AP in the medulla are immunoreactive to TH-antibody, some of these nuclei may innervate the GVC (Ito, Mukuda & Ando, submitted). Indeed, the GVC activity was inhibited by an electrical stimulation on the LX, but the inhibitory effect was not blocked by yohimbine (Ito & Ando, in preparation). Therefore, it is likely that the GVC activity is regulated by many inputs and the neuronal circuit on the GVC seems to be complicated.