Summary
The hypothalamic arcuate nucleus (ARCN) of female rats at 5, 20, 45 and 90 days of age was examined ultrastructurally. Axodendritic and axosomatic synapses were counted in 18,000 μm2 area of the ARCN in each brain. Axodendritic and axosomatic synapses in the ARCN of day 5 rats were very small in number. Axon terminals contained small spherical vesicles (SSVs, 40–60 nm in diameter). Occasionally large granular vesicles (LGVs, 75–130 nm in diameter) were found to coexist with SSVs in the endings. Pre- and postsynaptic membranes were thin. The ARCN at this age exhibited a large extracellular space which decreased with advancing age. In day 20 rats, axodendritic and axosomatic synapses increased in number up to about one-half of those of day 45 or day 90 animals. Synaptic vesicles increased in number and mitochondria were frequently encountered in the axon terminals. Pre- and postsynaptic membranes became thicker than those of day 5 rats. Further increase in the number of axodendritic and axosomatic synapses in the ARCN of day 45 rats was observed, and there were no significant difference in the morphology and incidence of synapses between day 45 and day 90 rats. Synaptic vesicles were numerous and pre- and postsynaptic membranes were thick. In tissue incubated with 5-hydroxydopamine (5-OH-DA) before fixation, small granular vesicles (SGVs, about 50 nm in diameter) which were labeled with 5-OH-DA were detected in a certain number of endings in all material taken from each age group, but the incidence of synapses containing SGVs was usually low. From these results, it can be proposed that an increase in the number of synapses in the ARCN is correlated with functional maturation of the ARC neurons.
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Adamo, N.J.: Ultrastructural features of the lateral preoptic area, median eminence and arcuate nucleus of the rat. Z. Zellforsch. 127, 483–491 (1972)
Aghajanian, G.K., Bloom, F.E.: The formation of synaptic junctions in developing rat brain: a quantitative electron microscopic study. Brain Res. 6, 716–727 (1967)
Ajika, K., Hökfelt, T.: Ultrastructural identification of catecholamine neurons in the hypothalamic periventricular-arcuate nucleus-median eminence complex with special reference to quantitative aspects. Brain Res. 57, 97–117 (1973)
Arai, Y.: Sexual differentiation and development of the hypothalamus and steroid-induced sterility. In: Neuroendocrine control (Yagi, K. and Yoshida, S., eds.), pp. 27–55. Tokyo: Univ. Tokyo Press 1973
Barraclough, C.A.: Modifications in reproductive function after exposure to hormones during the prenatal and early postnatal period. In: Neuroendocrinology II (Martini, L. and Ganong, W.F., eds.), pp. 61–99. New York: Academic Press 1967
Barry, J., Dubois, M.P.: Carette, B.: Immunofluorescence study of the preoptico-infundibular LRF neurosecretory pathway in the normal, castrated or testosterone-treated male guinea pig. Endocrinology 95, 1416–1423 (1974)
Björklund, A., Falck, B., Hromek, F., Owman, C., West, K.A.: Identification and terminal distribution of the tubero-hypophyseal monoamine fibre systems in the rat by means of stereotaxic and microspectrofluorimetric techniques. Brain Res. 17, 1–23 (1970)
Bondareff, W., Pysh, J.J.: Distribution of the extracellular space during postnatal maturation of rat cerebral cortex. Anat. Rec. 160, 773–780 (1968)
Brawer, J.R.: The role of the arcuate nucleus in the brain-pituitary-gonad axis. J. comp. Neurol. 143, 411–446 (1971)
Caley, D.W., Maxwell, D.S.: An electron microscopic study of neurons during postnatal development of the rat cerebral cortex. J. comp. Neurol. 133, 17–44 (1968)
Clattenburg, R.E.: Ultrastructure of hypothalamic neurons and of the median eminence. Canad. J. Neurol. Sci 1, 40–58 (1974)
Clementi, F., Ceccarelli, B.: Fine structure of rat hypothalamic nuclei. In: The hypothalamus (Martini, L., Motta, M. and Fraschini, F., eds.), pp. 17–44. New York: Academic Press 1970
Crighton, D.B., Schneider, H.P.G., McCann, S.M.: Localization of LH-releasing factor in the hypothalamus and neurohypophysis as determined by in vitro method. Endocrinology 87, 323–329 (1970)
Csernus, V., Lengvári, I., Halász, B.: Further studies of ACTH secretion from pituitary grafts in the hypophysiotropic area. Neuroendocrinology 17, 18–26 (1975)
Flament-Durand, J., Desclin, L.: The hypophysiotropic area. In: The hypothalamus (Martini, L., Motta, M. and Fraschini, F., eds.), pp. 245–257. New York: Academic Press 1970
Fuxe, K., Hökfelt, T.: Further evidence for the existence of tubero-infundibular dopamine neurons. Acta physiol. scand. 66, 245–246 (1966)
Gorski, R.A.: Gonadal hormones and the perinatal development of neuroendocrine function: In: Frontiers in neuroendocrinology, 1971 (Martini, L. and Ganong, W.F., eds), pp. 237–290. New York: Oxford Univ. Press 1971
Halász, B.: The endocrine effects of isolation of the hypothalamus from the rest of the brain. In: Frontiers in neuroendocrinology, 1969 (Ganong, W.F. and Martini, L., eds.), pp. 307–342. New York: Oxford Univ. Press 1969
Hayashi, S., Gorski, R.A.: Critical exposure time for androgenization by intracranial crystals of testosterone propionate in neonatal female rats. Endocrinology 94, 1161–1167 (1974)
Hökfelt, T.: In vitro study on central and peripheral monoamine neurons at the ultrastructural level. Z. Zellforsch. 91, 1–74 (1968)
Hyyppä, M.: A histochemical study of the primary catecholamines in the hypothalamic neurons of the rat in relation to the ontogenetic and sexual differentiation. Z. Zellforsch. 98, 550–560 (1969)
Ibata, Y., Nojyo, Y., Matsuura, T., Yoshikawa, H., Sano, Y.: Electron microscopy of the arcuate nucleus of normal and 5-hydroxydopamine treated cats. Cell Tiss. Res. 160, 139–153 (1975)
Jaim Etcheverry, G., Pellegrino de Iraldi, A.: Ultrastructure of neurons in the arcuate nucleus of the rat. Anat. Rec. 160, 239–254 (1968)
Johnson, R., Armstrong-James, M.: Morphology of superficial postnatal cerebral cortex with special reference to synapses. Z. Zellforsch. 110, 540–558 (1970)
King, J.C., Williams, T.H., Gerall, A.A.: Transformation of hypothalamic arcuate neurons. I. Changes associated with stages of the estrous cycle. Cell Tiss. Res. 153, 497–515 (1974)
Knigge, K.M., Silverman, A.J.: Anatomy of the endocrine hypothalamus. In: Handbook of physiology, Sect. 7: Endocrinology IV, Part 1, (Greep, R.O. and Astwood, E.B., eds.), pp. 1–32. Baltimore: The Williams and Wilkins Co. 1974
Kordon, C., Kerdelhué, B., Pattou, E., Jutisz, M.: Immunocytochemical localization of LHRH in axons and nerve terminals of the rat median eminence. Proc. Soc. exp. Biol. Med. (N.Y.) 147, 122–127 (1974)
Mazzuca, M.: Structure fine des cellules du noyau infundibulaire et de leurs afférences chez le cobaye. J. Microscopie 7, 135–144 (1968)
Mess, B.: Localization of production and mechanism of release of the releasing factors. In: Biological rhythms in neuroendocrine activity (Kawakami, M., ed.), pp. 54–72. Tokyo: Igaku Shoin Ltd. 1974
Nadler, R.D.: Intrahypothalamic locus for induction of androgen sterilization in neonatal female rats. Neuroendocrinology 9, 349–357 (1972)
Naik, D.V.: Immunoreactive LH-RH neurons in the hypothalamus identified by light and fluorescent microscopy. Cell Tiss. Res. 157, 423–436 (1975a)
Naik, D.V.: Immuno-electron microscopic localization of luteinizing hormone-releasing hormone in the arcuate nuclei and median eminence of the rat. Cell Tiss. Res. 157, 437–455 (1975b)
Oksche, A., Oehmke, H.J., Hartwig, H.G.: A concept of neuroendocrine cell complexes. In: Neurosecretion — the final neuroendocrine pathway. VI. International Symposium on neurosecretion, London 1973 (Knowles, F. and Vollrath, L., eds.), pp. 154–164. Berlin-Heidelberg-New York: Springer 1974
Olson, L., Seiger, Å.: Early prenatal ontogeny of central monoamine neurons in the rat: fluorescent histochemical observations. Z. Anat. Entwickl.-Gesch. 137, 301–316 (1972)
Palkovits, M., Arimura, A., Brownstein, M., Schially, A.V., Saavedra, J.M.: Luteinizing hormone-releasing hormone (LH-RH) content of the hypothalamic nuclei in rat. Endocrinology 95, 554–558 (1974)
Raisman, G., Field, P.M.: Anatomical considerations relevant to the interpretation of neuroendocrine experiments. In: Frontiers in neuroendocrinology, 1971 (Martini, L. and Ganong, W.F., eds.), pp. 3–44. New York: Oxford Univ. Press 1971a
Raisman, G., Field, P.M.: Sexual dimorphism in the preoptic area of the rat. Science 173, 731–733 (1971b)
Raisman, G., Field, P.M.: Sexual dimorphism in the neuropil of the preoptic area of the rat and its dependence on neonatal androgen. Brain Res. 54, 1–29 (1973)
Ratner, A., Adamo, N.J.: Arcuate nucleus region in androgen-sterilized female rats: ultrastructural observations. Neuroendocrinology 8, 26–35 (1971)
Reynolds, E.S.: The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J. Cell Biol. 17, 208–212 (1963)
Richards, J.G., Tranzer, J.P.: The ultrastructural localisation of amine storage sites in the central nervous system with the aid of a specific marker, 5-hydroxydopamine. Brain Res. 17, 463–469 (1970)
Sawyer, C.H.: First Geoffrey Harris memorial lecture. Some recent developments in brain-pituitary-ovarian physiology. Neuroendocrinology 17, 97–124 (1975)
Sétáló, G., Vigh, S., Schally, A.V., Arimura, A., Flerkó, B.: LH-RH-containing elements in the rat hypothalamus. Endocrinology 96, 135–142 (1975)
Tranzer, J.P., Thoenen, H.: Electron microscopic localization of 5-hydroxydopamine (3, 4, 5-trihydroxy-phenyl-ethylamine), a new “false” sympathetic transmitter. Experientia (Basel) 23, 743–745 (1967)
Vernadakis, A., Woodbury, D.M.: Cellular and extracellular spaces in developing rat brain. Arch. Neurol. (Chic.) 12, 284–293 (1965)
Voeller, K., Pappas, G.D., Purpura, D.P.: Electron microscopic study of development of cat superficial neocortex. Exp. Neurol. 7, 107–130 (1963)
Watson, M.L.: Staining of tissue sections for electron microscopy with heavy metals. J. biophys. biochem. Cytol. 4, 475–478 (1958)
Woodward, D.J., Hofter, B.J., Siggins, G.R., Bloom, F.E.: The ontogenetic development of synaptic junctions, synaptic activity and responsiveness to neurotransmitter substances in rat cerebellar Purkinje cells. Brain Res. 34, 73–97 (1971)
Zambrano, D.: The arcuate complex of the female rat during the sexual cycle. An electron microscopic study. Z. Zellforsch. 93, 560–570 (1969)
Zambrano, D., De Robertis, E.: The effect of castration upon the ultrastructure of the rat hypothalamus. II. Arcuate nucleus and outer zone of the median eminence. Z. Zellforsch. 87, 409–421 (1968)
Zimmerman, E.A., Hsu, K.C., Ferin, M., Kozlowski, G.P.: Localization of gonadotropin-releasing hormone (Gn-RH) in the hypothalamus of the mouse by immunoperoxidase technique. Endocrinology 95, 1–8 (1974)
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Acknowledgements. The authors wish to thank Prof. T. Kojima, Nihon University, for valuable suggestions during the initial stage of this study. This study was supported by grants from the Ministry of Education of Japan
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Matsumoto, A., Arai, Y. Developmental changes in synaptic formation in the hypothalamic arcuate nucleus of female rats. Cell Tissue Res. 169, 143–156 (1976). https://doi.org/10.1007/BF00214204
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DOI: https://doi.org/10.1007/BF00214204