Preserved Number of Entorhinal Cortex Layer II Neurons in Aged Macaque Monkeys

• Published in: Neurobiology of aging 1997-09, Vol.18 (5), p.549-553
• Main Authors: Gazzaley, A.H, Thakker, M.M, Hof, P.R, Morrison, J.H
• Format: Article
• Language: English
• Subjects: Aging; Aging - pathology; Animals; Biological and medical sciences; Development. Senescence. Regeneration. Transplantation; Entorhinal cortex; Entorhinal Cortex - cytology; Entorhinal Cortex - growth & development; Fundamental and applied biological sciences. Psychology; Image Processing, Computer-Assisted; Life Sciences (General); Macaca mulatta; Macaque monkey; Neurons - physiology; Optical fractionator; Receptors, N-Methyl-D-Aspartate - metabolism; Space life sciences; Stereology; Vertebrates: nervous system and sense organs
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/S0197-4580(97)00112-7

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.