title: Preserved number of entorhinal cortex layer II neurons in aged macaque monkeys.
abstract: The perforant path, which consists of the projection from the layer II neurons of the entorhinal cortex to the outer molecular layer of the dentate gyrus, is a critical circuit involved in learning and memory formation. Accordingly, disturbances in this circuit may contribute to age-related cognitive deficits. In a previous study, we demonstrated a decrease in N-methyl-D-aspartate receptor subunit 1 immunofluorescence intensity in the outer molecular layer of aged macaque monkeys. In this study, we used the optical fractionator, a stereological method, to determine if a loss of layer II neurons occurred in the same animals in which the N-methyl-D-aspartate receptor subunit 1 alteration was observed. Our results revealed no significant differences in the number of layer II neurons between juvenile, young adult, and aged macaque monkeys. These results suggest that the circuit-specific decrease in N-methyl-D-aspartate receptor subunit 1 reported previously occurs in the absence of structural compromise of the perforant path, and thus may be linked to an age-related change in the physiological properties of this circuit.
authors.affiliation: Neurobiology of Aging Laboratories, Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Gazzaley
authors.forename: M M
authors.initials: MM
authors.lastname: Thakker
authors.forename: P R
authors.initials: PR
authors.lastname: Hof
authors.forename: J H
authors.initials: JH
authors.lastname: Morrison
mesh_terms: D000375:Aging / Q000473:pathology*; D000818:Animals; D018728:Entorhinal Cortex / Q000166:cytology* / Q000254:growth & development*; D007091:Image Processing, Computer-Assisted; D008253:Macaca mulatta; D009474:Neurons / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate