Effects of exercise training on dendritic morphology in the cardiorespiratory and locomotor centers of the mature rat brain

Nelson, Amanda J., et al. "Effects of exercise training on dendritic morphology in the cardiorespiratory and locomotor centers of the mature rat brain." Journal of Applied Physiology 108.6 (2010): 1582-1590. This study was very similar to Nick's structural study in that it examined morphological plasticity of neurons involved with cardiac sympathetic modulation. However, this study looked at respiratory and locomotor brain regions as well. Another distinguishable difference between the two studies was the age at which the animals began exercising. This study was interested in examining neural plasticity in adult rats unrelated to development. To do this they started exercise training the rats only after the animals were 91 days old, and maintained spontaneous free-running for 50 days following initiation. The reason I was interested in this paper particularly was because we are having trouble imaging the smaller rats (~99g), and in order to do a longitudinal study it is imperative we collect reliable data at each time point. I thought this may be helpful because we have not looked at plasticity in rats older than ~18 weeks of age 11-13wks running. These rats were 13 weeks old when the exercise training began and ~20 weeks old when the sholl analysis was done looking at dendritic arborization. Unfortunately, no differences were found between exercising and sedentary animals dendritic branching within the RVLM at 20 weeks of age. Based on these results I would avoid prolonging my longitudinal study looking at neuronal activity plasticity to an older subset of rats if at all possible, which I believe is. They did, however,see structural plasticity in other brain regions at this stage in life, including in the NTS, posterior hypothalamus, periaqueductal gray, and the cuneiform nucleus. In the majority of these brain regions though, they found that the effect size was not as great in older rats as it was in the younger rats. One of the major limitations to this study was that they were not able to differentiate if the decreasing plasticity with age was due to increases in age, or decreases in running because older rats naturally run less than their younger counter parts. I wondered if they looked at a correlation between individual animals running and plasticity because this show evidence for one possible versus the other. ~JI