Catecholamines serve as a neuromodulators of many behavioral and endocrine responses in vertebrates including amphibians. However, the neuroanatomical studies on catecholamines, especially in the tadpole brain are limited. In this study, we report the distribution of catecholaminergic neurons in different areas of the brain in the tadpole of Microhyla ornata at metamorphic climax stage. Application of antisera against tyrosine hydroxylase (TH) revealed the presence of catecholaminergic cells and fibres in the olfactory bulb, the telencephalon, the diencephalon, the mesencephalon, the spinal cord and the pituitary gland. Whereas densest aggregations of TH-ir fibres were noticed in the nucleus accumbens and the amygdala pars medialis regions of the telencephalon, highest population of TH-ir cells with dorsolaterally and rostrocaudally oriented fibres was observed in the preoptic area. Larger and distinct TH-ir cell bodies along with few dorsolaterally oriented TH-ir fibres were scattered throughout the suprachiasmatic nucleus. While moderate to intensely stained clusters of TH-ir cells were observed in dorsal and ventral hypothalamic regions, conspicuous TH-ir cells and fibres were seen in the pars distalis of the pituitary gland. In the nucleus tuberculi posterioris, numerous moderate sized TH-ir cells were found along the margin of the third ventricle and the fibres from this region were oriented dorsolaterally towards the torus semicircularis and tectal regions, whereas well organized largest TH-ir cells and fibres were seen in the tegmentum. In the spinal cord, medium sized TH-ir cells along with numerous laterally running fibres were encountered. Overall, widespread distribution of the TH-ir cells and fibres in the brain and the pituitary gland of the tadpole suggest diverse roles for the catecholamines in regulation of locomotion, olfaction, skin pigmentation and endocrine responses during final stages of metamorphosis in M. ornata.

中文翻译：

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窄口蛙蝌蚪脑中酪氨酸羟化酶免疫反应神经元

儿茶酚胺作为脊椎动物（包括两栖动物）的许多行为和内分泌反应的神经调节剂。然而，关于儿茶酚胺，特别是蝌蚪脑中儿茶酚胺的神经解剖学研究是有限的。在这项研究中，我们报告了在变态高潮阶段的小鬣狗​​蝌蚪大脑不同区域中儿茶酚胺能神经元的分布。抗酪氨酸羟化酶 (TH) 抗血清的应用表明，在嗅球、端脑、间脑、中脑、脊髓和垂体中存在儿茶酚胺能细胞和纤维。而在伏核和端脑的杏仁核内侧部区域观察到最密集的 TH-ir 纤维聚集，在视前区观察到具有背外侧和尾尾定向纤维的 TH-ir 细胞数量最多。较大且独特的 TH-ir 细胞体以及少量背外侧定向的 TH-ir 纤维散布在整个视交叉上核。虽然在下丘脑背侧和腹侧区域观察到中度至重度染色的 TH-ir 细胞簇，但在垂体的远端部分可见明显的 TH-ir 细胞和纤维。在后核结核中，沿第三脑室边缘发现了许多中等大小的 TH-ir 细胞，该区域的纤维朝向半圆环和顶盖区域的背外侧定向，而组织良好的最大 TH-ir 细胞和纤维位于见于被盖。在脊髓中，遇到了中等大小的 TH-ir 细胞以及许多横向运行的纤维。总体而言，TH-ir 细胞和纤维在大脑和蝌蚪的脑垂体中的广泛分布表明儿茶酚胺在 M. ornata 变态的最后阶段在调节运动、嗅觉、皮肤色素沉着和内分泌反应方面发挥着不同的作用。