Postnatal Development of GABAergic Neurons in the Rat Cerebellum
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Postnatal Development of GABAergic Neurons in the Rat Cerebellum S. M. Zimatkin and O. A. Karniushko
UDC 612.827:547.466.34:612.65]-092.9
Translated from Morfologiya, 157, No. 1, pp. 13–17, January–February, 2020. Original article submitted July 31, 2017. Revised version received November 29, 2019. Objective. To evaluate the dynamics of the formation of GABAergic neurons in the cortex and nuclei of the developing cerebellum of white rats during postnatal ontogeny using immunohistochemical detection of glutamate decarboxylase (GDC). Materials and methods. Studies were carried out on 16 mongrel white rats on days 2, 7, and 15 (the early postnatal period) and on day 45 (the pubertal period) after birth. GABAergic neurons were detected immunohistochemically using GAD67 primary mouse monoclonal antibodies to GDC, this being the enzyme synthesizing γ-aminobutyric acid. GDC immunoreactivity was studied on paraffin sections of the paravermal zone of the cerebellum. Results. GDC was detected in the cytoplasm of the bodies of all types of GABAergic neurons in the cerebellar cortex on postnatal day 2. The cytoplasm of the bodies of piriform (Purkinje) cells (PC) showed a maximum level on day 7, while their dendrites showed a maximum on day 15, and there was a subsequent reduction in large stellate cells (Golgi cells, GC) on day 45. GDC immunoreactivity in the axons of stellate and basket neurons was significantly elevated by day 45 and these formed plexuses (baskets) around PC bodies. GABAergic synapses were detected in the cerebellar cortex on day 7 and reached maximal development on day 45. The cytoplasm of the bodies of some neurons in the globose and emboliform nuclei of the cerebellum showed moderate GDC immunoreactivity in two-day-old rats. On day 7, GDC-immunopositive fibers and axodendritic synapses were seen between neurons, with axosomatic synapses on neuron bodies, the number of these structures increasing by day 45. Conclusions. Immunohistochemical studies of GDC clearly identified the dynamics of postnatal structural transformations of the bodies, processes, and synaptic terminals of GABAergic neurons in the rat cerebellum. Keywords: rat cerebellum, postnatal development, GABAergic neurons, glutamate decarboxylase.
Introduction. The main inhibitory neurotransmitter in the cerebellum is γ-aminobutyric acid (GABA). Of the seven major types of neuron in the cerebellar cortex, five are GABAergic. All GABAergic neurons in the cerebellar cortex and nuclei are formed from the neuroepithelium of the fourth ventricle and then migrate to take up their definitive positions and differentiate [14, 15]. Basket cell precursors in rats form on days 2–17, while stellate neurons develop on days 4–19 of postnatal development. They reach their final positions in the molecular layer on days 7–21 after birth [14, 15], differentiate, and establish GABAergic
synaptic contacts with piriform (Purkinje) neurons (PC). PC precursors in rats form on days 13–16 of embryogenesis [4]. Postmigration PC undergo dendrite remodeling in the cereb
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