title: Maintenance of inhibitory interneurons and boutons in sensorimotor cortex between middle and old age in Fischer 344 X Brown Norway rats.
abstract: Ultrastructurally identified inhibitory synapses in layer II of rat sensorimotor cortex decline between middle and old age [Poe, B.H., Linville, C., Brunso-Bechtold, J., 2001. Age-related decline of presumptive inhibitory synapses in the sensorimotor cortex as revealed by the physical disector. J. Comp. Neurol. 439, 65-72]. The current study investigated whether a loss or shrinkage of gamma-aminobutyric acid (GABA)ergic interneurons contribute to that decline. Coronal sections from middle-aged (15-17 months) and old (25-29 months) Fischer 344 X Brown Norway male rats were immunoreacted with antibodies to the GABA synthesizing enzyme glutamic acid decarboxylase (GAD); the calcium-binding protein parvalbumin (PV), or the neuronal marker NeuN. The number of GAD-immunoreactive (IR), PV-IR, and NeuN-IR cells were determined stereologically using the optical disector technique and the cross-sectional areas of GAD-IR cells were measured in layers II/III, IV, V and VI of sensorimotor cortex. Neither the number of GAD-IR or NeuN-IR cells, nor the size of GAD-IR cells, declined significantly between middle and old age. A modest decline in the PV-IR subset of inhibitory interneurons was observed, predominantly due to changes in layers V and VI. Stereological analysis of layer II/III GAD-IR boutons revealed a stability of immunocytochemically identified inhibitory terminals. Taken together, these results indicate a general maintenance of overall GABAergic neurons in sensorimotor cortex between middle and old age and the loss of ultrastructurally identified inhibitory synapses may be due to the decline of a subset of GABAergic terminals.
authors.affiliation: Department of Neurobiology & Anatomy, Wake Forest University Health Sciences, Winston-Salem, NC 27157-1010, USA. lshi@wfubmc.edu
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Hui
authors.initials: H
authors.lastname: Pang
authors.forename: Martha Constance
authors.initials: MC
authors.lastname: Linville
authors.forename: Angela Nicole
authors.initials: AN
authors.lastname: Bartley
authors.forename: Anne Elizabeth
authors.initials: AE
authors.lastname: Argenta
authors.forename: Judy Karen
authors.initials: JK
authors.lastname: Brunso-Bechtold
mesh_terms: D000375:Aging; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology* / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007395:Interneurons / Q000166:cytology* / Q000378:metabolism; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010320:Parvalbumins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010320:Parvalbumins; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase