Summary
Previous studies with the Nauta technique have established that fibres which originate in two important areas — the hippocampus and the hypothalamus — converge upon the cells of the septal nuclear complex. The purpose of this study was to investigate the anatomical basis of how the septal cells could differentiate between fibres from the two sources. Differences in the mode of termination of these two systems have been studied quantitatively at the electron microscope level by using the orthograde degeneration of terminals after lesions of the fimbria and the medial forebrain bundle. In the medial septal nucleus, the hippocampal fibres account for 35% of the terminals, and in the lateral septal nucleus, 43% of the terminals on the same side and a further 13% on the opposite side. These terminals are at least 98% axodendritic and 91% of them contain predominantly clear synaptic vesicles of 500 Å diameter. The hypothalamic fibres are the source of up to 19% of the axodendritic terminals in the medial septal nucleus, but considerably fewer in the lateral septal nucleus. In contrast to the hippocampal afferents, the hypothalamo-septal system has two characteristic features: firstly, the fibres give rise to up to 24% of the axosomatic terminals in the medial septal nucleus, and secondly, 63% of the terminals contain a population of vesicles with significantly higher proportions of dense centred vesicles of 800–1000 Å diameter.
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References
Alksne, J.F., T.W. Blackstad, F. Walberg and L.E. White jr.: Electron microscopy of axon degeneration: a valuable tool in experimental neuroanatomy. Ergebn. Anat. Entwickl.-Gesch. 39, 3–31 (1966).
Andén, N.-E., A. Dahlström, K. Fuxe, K. Larsson, L. Olson and U. Ungerstedt: Ascending monoamine neurons to the telencephalon and diencephalon. Acta physiol. scand. 67, 313–326 (1966).
Andersen, P., and J.C. Eccles: Locating and identifying postsynaptic inhibitory synapses by the correlation of physiological and histological data. Symp. Biol. Hung. 5, 219–242 (1965).
Bondareff, W., and B. Gordon: Submicroscopic localization of norepinephrine in sympathetic nerves of rat pineal. J. Pharmacol. exp. Ther. 153, 42–47 (1966).
Cajal, S. Ramón Y: Histologie du système nerveux de l'homme et des vertébrés. Paris: Maloine 1911.
Coupland, R.E.: Electron microscopic observations on the structure of the rat adrenal medulla. II. Normal innervation. J. Anat. (Lond.) 99, 255–272 (1965).
Cowan, W.M., R.W. Guillery and T.P.S. Powell: The origin of the mamillary peduncle and other hypothalamic connexions from the midbrain. J. Anat. (Lond.) 98, 345–363 (1964).
De Groot, J.: The rat forebrain in stereotaxic coordinates. Trans. Royal Neth. Acad. Sci. 52, 1–40 (1959).
Fuxe, K., T. Hökfelt and O. Nilsson: A fluorescence and electronmicroscopic study on certain brain regions rieh in monoamine terminals. Amer. J. Anat. 117, 33–46 (1965).
— and S. Reinius: A fluorescence and electron microscopic study on central monoamine nerve cells. Anat. Rec. 155, 33–40 (1966).
Grant, G., and J. Westman: Degenerative changes in dendrites central to axonal transection. Experientia (Basel) 24, 169–170 (1968).
Gray, E.G.: Axo-somatic and axo-dendritic synapses of the cerebral cortex: an electron microscope study. J. Anat. (Lond.) 93, 420–433 (1959).
—, and R.W. Guillery: Synaptic morphology in the normal and degenerating nervous system. Int. Rev. Cytol. 19, 111–182 (1965).
Grillo, M.A., and S.L. Palay: Granule-containing vesicles in the autonomic nervous system. In: Fifth International Congress for Electron Microscopy. Ed. by S.S. Breese. Vol. 2, Ul. New York: Academic Press 1962.
Guillery, R.W.: Degeneration in the hypothalamic connexions of the albino rat. J. Anat. (Lond.) 91, 91–115 (1957).
Hökfelt, T.: The effect of reserpine on the intraneuronal vesicles of rat vas deferens. Experientia (Basel) 22, 56 (1966a).
—: Electron microscopic observations on nerve terminals in the intrinsic muscles of the albino rat iris. Acta physiol. scand. 67, 255–256 (1966b).
—: On the ultrastructural localization of noradrenaline in the central nervous system of the rat. Z. Zellforsch. 79, 110–117 (1967a).
—: Electron microscopic studies on brain slices from regions rich in catecholamine nerve terminals. Acta physiol. scand. 69, 119–120 (1967b).
Karnovsky, M.J.: A formaldehyde-glutaraldehyde fixative of high osmolatily for use in electron microscopy. J. Cell. Biol. 27, 137 A (Abstr.) (1965).
McMahan, U.J.: Fine structure of synapses in the dorsal nucleus of the lateral geniculate body of normal and blinded rats. Z. Zellforsch. 76, 116–146 (1967).
Mugnaini, E., and F. Walberg: An experimental electron microscopical study on the mode of termination of oerebellar corticovestibular fibres in the cat lateral vestibular nucleus (Deiters' nucleus). Exp. Brain Res. 4, 212–236 (1967).
— and A. Brodal: Mode of termination of primary vestibular fibres in the lateral vestibular nucleus. Exp. Brain Res. 4, 187–211 (1967).
— and E. Haughlie-Hanssen: Observations on the fine structure of the lateral vestibular nucleus (Deiters' nucleus) in the cat. Exp. Brain Res. 4. 146–186 (1967).
Palay, S.L., S.M. McGeeRussell, S. Gordon and M.A. Grillo: Fixation of neural tissues for electron microscopy by perfusion with solutions of osmium tetroxide. J. Cell. Biol. 12 385–410 (1962).
Pellegrino de Iraldi, A., H. Farini Duggan and E. De Robertis: Adrenergic synaptic vesicles in the anterior hypothalamus of the rat. Anat. Rec. 145, 521–531 (1963).
Pfeifer, A.K., D.Szabó, M. Palkovits and I. Ökrös: Correlation between noradrenaline content of the brain and the number of granular vesicles in rat hypothalamus during Nialamid administration. Exp. Brain Res. 5, 79–86 (1968).
Raisman, G.: The connexions of the septum. Brain 89, 317–348 (1966).
Raisman, G. Neuronal plasticity in the septal nuclei of the adult rat. Brain Res. (1969) [in press].
Ramón-Moliner, E., and W.J.H. Nauta: The isodendritic core of the brain stem. J. comp. Neurol. 126, 311–336 (1966).
Richardson, K. C.: The fine structure of the albino rabbit iris with special reference to the identification of adrenergic and cholinergic nerves and nerve endings in its intrinsic muscles. Amer. J. Anat. 114, 173–205 (1964).
—, L. Jarett and E.H. Finke: Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain Technol. 35, 313–323 (1960).
Shute, C.C.D., and P.R. Lewis: The ascending cholinergic reticular system: neocortical, olfactory and subcortical projections. Brain 90, 497–520 (1967).
Taxi, J.: Contribution a l'étude des connexions des neurones moteurs du système nerveux autonome. Ann. Sci. nat. Zool. (Paris) 7, 413–674 (1965).
Uchizono, K: Characteristics of excitatory and inhibitory synapses in the central nervous system of the cat. Nature (Lond.) 207, 642–643 (1965).
Walberg, F.: An electron microscopic study of terminal degeneration in the inferior olive of the cat. J. comp. Neurol. 125, 205–221 (1965).
—: The fine structure of the cuneate nucleus in normal cats and following interruption of afferent fibres. Exp. Brain Res. 2, 107–128 (1966).
Wolfe, D.E., L.T. Potter, K.C. Richardson and J. Axelrod: Localizing tritiated norepinephrine in sympathetic axons by electron microscopic autoradiography. Science 138, 440–442 (1962).
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Raisman, G. A comparison of the mode of termination of the hippocampal and hypothalamic afferents to the septal nuclei as revealed by electron microscopy of degeneration. Exp Brain Res 7, 317–343 (1969). https://doi.org/10.1007/BF00237319
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DOI: https://doi.org/10.1007/BF00237319