title: Growth and refinement of excitatory synapses in the human auditory cortex.
abstract: We had earlier demonstrated a neurofilament-rich plexus of axons in the presumptive human auditory cortex during fetal development which became adult-like during infancy. To elucidate the origin of these axons, we studied the expression of the vesicular glutamate transporters (VGLUT) 1 and 2 in the human auditory cortex at different stages of development. While VGLUT-1 expression predominates in intrinsic and cortico-cortical synapses, VGLUT-2 expression predominates in thalamocortical synapses. Levels of VGLUT-2 mRNA were higher in the auditory cortex before birth compared to postnatal development. In contrast, levels of VGLUT-1 mRNA were low before birth and increased during postnatal development to peak during childhood and then began to decrease in adolescence. Both VGLUT-1 and VGLUT-2 proteins were present in the human auditory cortex as early as 15GW. Further, immunohistochemistry revealed that the supra- and infragranular layers were more immunoreactive for VGLUT-1 compared to that in Layer IV at 34GW and this pattern was maintained until adulthood. As for VGLUT-1 mRNA, VGLUT-1 synapses increased in density between prenatal development and childhood in the human auditory cortex after which they appeared to undergo attrition or pruning. The adult pattern of VGLUT-2 immunoreactivity (a dense band of VGLUT-2-positive terminals in Layer IV) also began to appear in the presumptive Heschl's gyrus at 34GW. The density of VGLUT-2-positive puncta in Layer IV increased between prenatal development and adolescence, followed by a decrease in adulthood, suggesting that thalamic axons which innervate the human auditory cortex undergo pruning comparatively late in development.
authors.affiliation: Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India.
authors.forename: Arvind Singh
authors.initials: AS
authors.lastname: Pundir
authors.affiliation: Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India.
authors.forename: Utkarsha A
authors.initials: UA
authors.lastname: Singh
authors.affiliation: Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Ahuja
authors.affiliation: Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India.
authors.forename: Sonal
authors.initials: S
authors.lastname: Makhija
authors.affiliation: Department of Forensic Medicine, Maulana Azad Medical College, Bahadur Shah Zafar Marg, New Delhi, 110002, India.
authors.forename: P C
authors.initials: PC
authors.lastname: Dikshit
authors.affiliation: Department of Histopathology, Post Graduate Institute of Medical Education and Research, Sector-12, Chandigarh, 160012, India.
authors.forename: Bishan
authors.initials: B
authors.lastname: Radotra
authors.affiliation: Department of Obstetrics and Gynecology, Base Hospital, Delhi Cantonment, Delhi, 110010, India.
authors.forename: Praveen
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Department of Neuropathology, National Institute of Mental Health and Allied Sciences, Hosur Road, Bangalore, 560029, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Shankar
authors.affiliation: Department of Neuropathology, National Institute of Mental Health and Allied Sciences, Hosur Road, Bangalore, 560029, India.
authors.forename: Anita
authors.initials: A
authors.lastname: Mahadevan
authors.affiliation: Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110002, India.
authors.forename: T S
authors.initials: TS
authors.lastname: Roy
authors.affiliation: Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India. soumya@nbrc.ac.in.
authors.forename: Soumya
authors.initials: S
authors.lastname: Iyengar
mesh_terms: D000293:Adolescent; D000328:Adult; D001303:Auditory Cortex / Q000254:growth & development* / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D005260:Female; D047109:Fetal Development; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007382:Intermediate Filaments / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000166:cytology*; D012333:RNA, Messenger / Q000378:metabolism; D013569:Synapses; D050863:Synaptotagmin I / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism*; D055815:Young Adult
chemical_list: D012333:RNA, Messenger; C493476:SLC17A6 protein, human; C493464:SLC17A7 protein, human; D050863:Synaptotagmin I; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2
keywords: Cortico-cortical synapses; Human auditory cortex; Thalamocortical synapses; Vesicular glutamate transporters