Since the histochemical procedure for the demonstration of biogenic monoamines was developed by Falck and his coworkers,1)2) many investigators have revealed the catecholamine containing nerve fivers in the median eminence of amphibians,3) birds4)5) and mammals.6-10) These catecholamines have been assumed to be released into the hypophysial portal vessel system and participate in the control of the adenohypophysial function.11)12) In addition, several reports intimated that the releasing factors of ade nohypophysial hormones extracted from the mammalian hypothalamus seem to be the polypeptides.13-15) It was reported that in the teleosts the distribution of the catecholamine containing cells in the hypothalamus seem to be different from that of the higher ver tebrates.16) Among the bony fishes examined, the catecholamine containing neurons of the goldfish were found in the nucleus recessus lateralis hypothalami and nucleus recessus posterioris hypothalami.17)From the phylogenetic and ontogenetic points of view, little information is available in this field of researches. Hence, it was thought to be of value to examine the distribu tion of monoaminergic neurons in the hypothalamus of the lamprey and its ammocoete larva, as one of the most primitive vertebrates supposed to be lacking in the true median eminence and the hypophysial portal vessel system, and so forth.18) The central or neural control of adenohypophysial function of the lamprey, therefore, would be extremely weak.19)To make comparison with the bony fishes, the ice-goby was chosen and localization of monoamines was carried out, because this species has a peculiar pattern of the hypo thalamo-hypophysial complex.20)
Materials and MethodsSeveral adult specimens of both river lamprey, Entosphenus japonicus, and brook lamprey, Entosphenus reissneri, were used for the present histochemical and pharmacolo gical experiments (reserpinization). The mature adults of river lamprey were obtained from the estuaries of Shinano and Agano Rivers of Niigata Prefecture at the period of ascending the river in winter season or in May for spawning. The adults and ammocoete
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