New Rodent Study Shows CR Benefits Synapses in the Hippocampus

[Dean Pomerleau]

CR is known to improve spatial learning and memory in rodents on tasks like the Morris water maze. But it is a matter of some controversy as to whether this improvement is due to beneficial effects of CR on memory/cognition, or whether the lean CR rodents can just swim better [2][3].

 

James Cain posted this new study [1] which speaks to this issue a bit. Researchers found that short-term CR in young rats resulted in beneficial changes in the microstructure of synapses in their hippocampus, part of the brain known to be important for spatial learning. 

 

So that is nice to see!

 

--Dean

 

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[1] Hippocampus. 2015 Sep 19. doi: 10.1002/hipo.22533. [Epub ahead of print]

 

Food restriction modifies ultrastructure of hippocampal synapses.

 

Babits R1, Szőke B, Sótonyi P1, Rácz B1.

 

Abstract

Consumption of high-energy diets may compromise health and may also impair cognition; these impairments have been linked to tasks that require hippocampal function. Conversely, food restriction has been shown to improve certain aspects of hippocampal function, including spatial memory and memory persistence. These diet-dependent functional changes raise the possibility that the synaptic structure underlying hippocampal function is also affected. To examine how short-term food restriction (FR) alters the synaptic structure of the hippocampus, we used quantitative electron microscopy to analyze the organization of neuropil in the CA1 stratum radiatum of the hippocampus in young rats, consequent to reduced food. While four weeks of FR did not modify the density, size, or shape of postsynaptic spines, the synapses established by these spines were altered, displaying increased mean length, and more frequent perforations of postsynaptic densities. That the number of perforated synapses (believed to be an indicator of synaptic enhancement) increased, and that the CA1 spine population had on average significantly longer PSDs suggests that synaptic efficacy of axospinous synapses also increased in the CA1. Taken together, our ultrastructural data reveal previously unrecognized structural changes at hippocampal synapses as a function of food restriction, supporting a link between metabolic balance and synaptic plasticity. This article is protected by copyright. All rights reserved.

© 2015 Wiley Periodicals, Inc.

KEYWORDS:

CA1; dietary restriction; electron microscopy; memory; synaptic plasticity

PMID: 26386363

 

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[2] Physiol Behav. 2008 Feb 27;93(3):560-9. Epub 2007 Oct 30.

Effects of chronic adult dietary restriction on spatial learning in the aged F344
x BN hybrid F1 rat.

Fitting S(1), Booze RM, Gilbert CA, Mactutus CF.

Author information:
(1)Program in Behavioral Neuroscience, Department of Psychology, University of
South Carolina, Columbia, SC 29208, USA. fitting@sc.edu <fitting@sc.edu>

Dietary restriction (DR) has been shown to increase life span and reduce disease
incidence across a variety of species. Recent research suggests that chronic
adult DR may also alter age-related cognitive decline. The purpose of this study
was twofold: (1) to examine the potential deficits in spatial learning ability in
the aged F344 x BN hybrid F1 rat with specific attention to the contributory
effects of motoric impairments and (2) to determine the influence of chronic
adult DR on any such impairments. The Morris water maze (MWM) task was employed
with a 1.8 m diameter tank, 10 cm2 escape platform, 28 degrees C water, and an
automated collapsing central starting platform. Spatial learning impairments in
the aged rats were evident on all dependent measures during training and the
probe test. Motoric function, as reflected in measures of strength and locomotion
demonstrated profound age-related performance impairments that were attenuated by
chronic adult DR. The present data also replicate previous reports, indicating
that DR attenuates the age-related impairments of performance in the MWM as
indexed by the latency measure in acquisition, but critically was dissociated
from any DR effect on measures of preference and, more critically, accuracy in
the probe test. Collectively, the most parsimonious interpretation of DR effects
on MWM performance would appear to be the preservation of motoric, and not
cognitive, function.

PMCID: PMC4041982
PMID: 18035382

 

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[3] J Gerontol A Biol Sci Med Sci. 2009 Aug; 64A(8): 850–859.

Published online 2009 May 6. doi:  10.1093/gerona/glp060

 

Influence of Calorie Restriction on Measures of Age-Related Cognitive Decline: Role of Increased Physical Activity

 

Christy S. Carter,corresponding author1,2,3 Christiaan Leeuwenburgh,1 Michael Daniels,4 and Thomas C. Foster3

 

Abstract

Controversy exists as to whether lifelong 40% calorie restriction (CR) enhances, has no effect on, or disrupts cognitive function during aging. Here, we report the effects of CR versus ad-lib feeding on cognitive function in male Brown Norway × Fisher344 rats across a range of ages (8–38 months), using two tasks that are differentially sensitive to age-related cognitive decline: object recognition and Morris water maze (MWM). All ages performed equally in object recognition, whereas, as a group, CR rats were impaired. In contrast, there was an age-related impairment in the MWM that was attenuated by CR as measured by time in proximity with and latency to reach the platform. Distance to the platform, a more sensitive measure, was not affected by CR. Finally, CR resulted in an overall increase in physical activity, one of several behavioral confounders to consider in the interpretation of cognitive outcomes in both tasks.

 

PMCID: PMC2709546