Effect of Pregnancy on Forced Exercise in Mice
During pregnancy and lactation, a wide range of metabolic changes occur, all of which exist to ensure a healthy pregnancy occurs. One of these reductions is exercise with women typically reducing their exercise levels, even early in pregnancy when there are no physical limitations of the fetus present. In mice, there are rapid reductions in voluntary exercise that occur early in pregnancy with these reductions being caused by the lactogenic hormone, prolactin. How exactly prolactin causes rapid reductions in voluntary exercise during early pregnancy remains unclear. To try and elucidate this phenomenon, we used a forced exercise paradigm in order to test whether prolactin affects the motivation to exercise or the capacity to exercise. Similar to rapid reductions in voluntary exercise, unpublished data has shown mice rapidly reduce their forced exercise capacity in early pregnancy. Recent data from our lab has shown a role for prolactin in acting on reward/motivation circuitry and unpublished data has shown a role for prolactin in thermoregulation. Based on this, the aim of this project was to begin to distinguish between these hypotheses using a forced exercise paradigm that eliminated self-motivation as a factor in exercise during pregnancy and caused increases in body temperature that we attempted to measure using thermal imaging. First, our forebrain prolactin receptor knock-out model was validated using RNAscope in-situ hybridisation with a significant reduction seen in prolactin receptor and GABA neuron colocalization in the medial preoptic area in our knock-out (Prlrlox/loxCamK2aCre) vs control (Prlrlox/lox) mice. Forced exercise capacity remained unchanged during early pregnancy with no observable effect of prolactin on this. Use of a novel peripheral thermal imaging protocol was able to detect changes in exercise-induced and environmental heat change induced changes in tail and eye temperatures. This included detecting differences in thermoregulatory responses to environmental heat change between pregnant and virgin as well as lactating and virgin control mice. The findings of the present study indicate that prolactin might cause previously seen reductions in voluntary exercise during pregnancy through a prolactin-mediated change in the reward/motivation circuitry.
Advisor: Grattan, David R; Ladyman, Sharon R
Degree Name: Bachelor of Science (Honours)
Degree Discipline: Neuroscience
Research Type: Dissertation
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