Region specific neuron loss in the aged canine hippocampus is reduced by enrichment

Siwak-Tapp, Christina T.; Head, Elizabeth; Muggenburg, Bruce A.; Milgram, Norton W.; Cotman, Carl W.

doi:10.1016/j.neurobiolaging.2006.09.018

« Previous Next »Neurobiology of Aging
Volume 29, Issue 1 , Pages 39-50, January 2008

Region specific neuron loss in the aged canine hippocampus is reduced by enrichment

Christina T. Siwak-Tapp
- Institute for Brain Aging and Dementia, University of California, 1226 Gillespie Neuroscience Research Facility, Irvine, CA 92697-4540, USA
- Corresponding author. Tel.: +1 949 824 6071; fax: +1 949 824 2071.
Elizabeth Head
- Institute for Brain Aging and Dementia, University of California, 1226 Gillespie Neuroscience Research Facility, Irvine, CA 92697-4540, USA
- Department of Neurology, University of California, 1226 Gillespie Neuroscience Research Facility, Irvine, CA 92697-4540, USA
Bruce A. Muggenburg
- Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr. SE., Albuquerque, NM 87108, USA
Norton W. Milgram
- University of Toronto, 1265 Military Trail, Scarborough, Ontario, Canada M1C 1A4
Carl W. Cotman
- Institute for Brain Aging and Dementia, University of California, 1226 Gillespie Neuroscience Research Facility, Irvine, CA 92697-4540, USA

Received 12 May 2006; received in revised form 20 September 2006; accepted 30 September 2006. published online 10 November 2006.

Abstract

Neuron loss within the hippocampus and entorhinal cortex occurs as a function of age in humans. We first tested the hypothesis that neuron loss occurs in the aged dog. The total unilateral number of neurons in the canine entorhinal cortex and subdivisions of the hippocampus from the left hemisphere were estimated using the optical fractionator. The brains from 5 old (13.0–15.0 years old) and 5 young (3.4–4.5 years old) beagle dogs were analyzed. The hilus of the hippocampus showed a significant loss of neurons (∼30%) in the aged dog brain compared to young. Differences were not detected in the remaining hippocampal subfields and entorhinal cortex. We further tested the hypothesis that an antioxidant fortified food or behavioral enrichment would reduce the age-related loss of hilar neurons. Behaviorally enriched aged dogs had more neurons in the hilus (∼18%) compared to aged controls. These results suggest that the aged canine hippocampus in the left hemisphere shows selective neuron loss and that behavioral enrichment may reduce this loss.

Keywords: Dog, Brain, Aging, Hippocampus, Neuron loss, Antioxidants, Enrichment