Mapping of functional brain activity in freely behaving rats during voluntary running using manganese-enhanced MRI: implication for longitudinal studies.

Eschenko O, Canals S, Simanova I, Beyerlein M, Murayama Y, Logothetis NK. Neuroimage. 2010 Feb 1;49(3):2544-55 I picked this paper because we’ve been running in to some confusion with our MeMRI studies. Of late, we’ve been taking a step back and trying to answer some basic questions about the technique and how to apply it to our area. This paper is interesting because it answers a question or two we were wondering about and we might be able to work in to our future studies. In this paper the authors wanted to look at different routes of manganese (Mn) administration and see how they affected the physical activity of rats. Why is this important? Because if you’re studying something like exercise, you probably want to do things in a way that won’t stop the animals from exercising. It turns out that both subcutaneous and intraperitoneal injections of Mn, which cause observable lethargy in rats, also cause significant dose-related decreases in spontaneous wheel-running. Since Mn is taken up over the course of hours dependent on physical activity, decreases in physical activity were seen to significantly limit activity-dependent Mn uptake. They looked at an alternative route of administration, slow infusion over days by using an osmotic minipump. They found that this method did not decrease physical activity or food/water intake, but still allowed for enhanced physical activity-dependent contrast after MRI imaging. -DH