| Abstract No.: | A-D1125 |
| Country: | Canada |
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| Title: | DIFFERENTIAL EFFECT OF EXPOSURE TO SHORT AND LONG TERM ENRICHED ENVIRONMENTS IN THE PLASTICITY OF ZINCERGIC, CORTICAL CIRCUITS |
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| Authors/Affiliations: | 1 Amy Nakashima; 1 Richard Dyck;
1 University of Calgary, AB, Canada
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| Content: | Objectives
Vesicular zinc within the mammalian telencephalon is in a unique position to modulate plasticity as this zinc is contained within a subset of glutamatergic neurons, released in an activity dependent manner, and has a number of effects on postsynaptic receptors. In the somatosensory cortex, staining for vesicular zinc reveals the topographical organization of the barrel cortex. The barrel cortex provides a powerful model to study plasticity, as endogenous plasticity can be easily induced in a non-invasive manner and localization of the effect is simple and precise. Previously, our laboratory has shown that the induction of plasticity in the barrel cortex is accompanied by age- and activity-dependent changes in vesicular zinc levels within the barrel compartments corresponding to the manipulated vibrissae. As enriched environments increase the propensity for plasticity and encourage natural vibrissae stimulation through the exploration of complex surroundings, we examined how placing mice in these environments following whisker plucking affected the regulation of vesicular zinc in the barrel cortex.
Materials and methods
Three groups of male C57BL/6 mice were placed in standard laboratory environments for two months following weaning. Following the bilateral removal of the c-row of vibrissae, each group of animals was placed into one of three environments: home cage, home cage with toy added, or an enrichment cage consisting of a bi-level cage with an assortment of toys as well as conspecifics. In addition, a fourth group was assessed, consisting of mice that were housed in an enriched environment both prior to and post-plucking. After whisker plucking, the mice remained in their assigned housing conditions for 6 hours, 48 hours, 7 days, or 14 days after which brains were processed for staining of vesicular zinc in the barrel cortex.
Results
Our results showed that, with increasing amounts of enrichment, the degree of zincergic plasticity also increased. However, the extent to which enhancement was observed appeared to be dependent on the likelihood of tactile exploration. After 6 hours, the greater zincergic response observed was in the minimally enriched group. At 48 hours, mice that had been reared in an enriched environment had the greatest change in vesicular zinc staining within the barrels corresponding to the removed vibrissae. At 7 days, the enriched animals still had an augmented response; a response mirrored in the mice reared in the deprived to enriched condition. By 14 days, while a significant difference is only observed between the deprived and deprived to enriched groups, a trend exists for the same differences as those at 7 days.
Conclusion
The data clearly indicate that the regulation of vesicular zinc homeostasis within the barrel cortex is dependent on the amount of tactile experience provided. While these results further support the role of vesicular zinc in cortical plasticity as the increases in plasticity that occur with environmental enrichment are matched by enhancements in vesicular zinc responses, it is apparent the duration and extent of enrichment are important factors in the observation of enhanced plasticity.
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