Summary
Glutamate decarboxylase (GAD)-positive and Golgi impregnated local circuit neurons of the hippocampal formation of five day old rats were examined in light and electron microscopic preparations. The ultrastructural features of these neurons were similar in both the dentate gyrus and CA1 area of Ammon's horn. Somata displayed a perikaryal cytoplasm rich in organelles but lacked organized Nissl bodies. Most nuclei showed intranuclear infoldings of varying degrees but no intranuclear sheets or rods were found. Somata and dendrites were contacted by relatively immature axon terminals that formed mainly symmetric synapses. The axons of local circuit neurons in both the dentate gyrus and Ammon's horn formed symmetric synapses with somata and dendrites of the principal neurons in these regions. Thus, both GAD-positive and Golgi-impregnated terminals of local circuit neurons were observed to form synapses with pyramidal and granule cells. These terminals were usually small and contained relatively few pleomorphic synaptic vesicles. The results show that a circuitry for inhibition is established in the 5 day old dentate gyrus and Ammon's horn, even though the local circuit neurons lack some of the typical adult ultrastructural features at this age.
Similar content being viewed by others
References
Amaral DG (1978) A Golgi study of cell types in the hilar region of the hippocampus in the rat. J Comp Neurol 182:851–914
Amaral DG, Kurz J (1985) The time of origin of cells demonstrating glutamic acid decarboxylase-like immunoreactivity in the hippocampal formation of the rat. Neurosci Lett 58:33–40
Bayer SA (1980) Development of the hippocampal region in the rat. I. Neurogenesis examined with 3H-thymidine autoradiography. J Comp Neurol 190:87–114
Cragg BG (1972) The development of synapses in cat visual cortex. Inv Ophthal 11:377–385
Crain B, Cotman C, Taylor D, Lynch G (1973) A quantitative electron microscopic study of synaptogenesis in the dentate gyrus of the rat. Brain Res 63:195–204
Dyson SE, Jones DG (1976) The morphological categorization of developing synaptic junctions. Cell Tiss Res 167:363–371
Fairén A, Peters A, Saldanha J (1977) A new procedure for examining Golgi impregnated neurons by light and electron microscopy. J Neurocytol 6:311–337
Frotscher M, Zimmer J (1987) GABAergic non-pyramidal neurons in intracerebral transplants of the rat hippocampus and fascia dentata: a combined light and electron microscopic immunocytochemical study. J Comp Neurol 259:266–276
Janigro D, Schwartzkroin PA (1988) Effects of GABA and baclofen on pyramidal cells in the developing rabbit hippocampus: an “in vitro” study. Dev Brain Res 41:171–184
Jones DG, Revell E (1970) The postnatal development of the synapse: a morphological approach utilizing synaptosomes. I. General features. II. Paramembranous densities. Z Zellforsch 111:179–194, 195–208
Loy R (1980). Development of afferent Iamination in Ammon's horn of the rat. Anat Embryol 159:257–275
Lübbers K, Wolff JR, Frotscher M (1985) Neurogenesis of GABAergic neurons in the rat dentate gyrus: a combined autoradiographic and immunocytochemical study. Neurosci Lett 62:317–322
Lübbers K, Frotscher M (1988) Differentiation of granule cells in relation to GABAergic neurons in the rat fascia dentata. Anat Embryol 178:119–127
Oertel WH, Mugnaini E, Schmechel DE, Tappaz ML, Kopin IJ (1982) The immunocytochemical demonstration of gamma aminobutyric acid-ergic neurons — methods and applications. In: V Chan-Palay, SL Palay (eds) Cytochemical methods of neuroanatomy. Liss, New York, pp 297–329
Ribak CE, Seress L (1983) Five types of basket cell in the hippocampal dentate gyrus: a combined Golgi and electron microscopic study. J Neurocytol 12:577–597
Seress L, Ribak CE (1988a) The development of GABAergic neurons in the rat hippocampal formation: an immunocytochemical study. Dev Brain Res 44:197–211
Seress L, Ribak CE (1988b) Basket cells of the dentate gyrus establish synaptic connections with granule cells in five day old rats. Soc Neurosci Abstr 14:578
Sternberger LA, Hardy PH, Curculis JJ, Meyer HG (1970) The unlabelled antibody-enzyme method of immunocytochemistry: preparation and properties of soluble antigen-antibody complex (horseradish peroxidase) and its use in identification of spirochetes. J Histochem Cytochem 18:315–333
Swann JW, Brady RJ, Martin DL (1989) Postnatal development of GABA-mediated synaptic inhibition in rat hippocampus. Neuroscience 28:551–561
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Seress, L., Frotscher, M. & Ribak, C.E. Local circuit neurons in both the dentate gyrus and Ammon's horn establish synaptic connections with principal neurons in five day old rats: a morphological basis for inhibition in early development. Exp Brain Res 78, 1–9 (1989). https://doi.org/10.1007/BF00230680
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00230680