Mapping of the habenulo-interpeduncular pathway in living mice using manganese-enhanced 3D MRI.

Magn Reson Imaging. 2006 Apr;24(3):209-15. Epub 2006 Jan 6. Watanabe T, Radulovic J, Boretius S, Frahm J, Michaelis T. I chose this paper because I've been wondering about intercerebroventricular (ICV) injections for MEMRI studies. In this paper, the authors wanted to use memri to map the habenula (Hb) , so they injected MnCl2 in to left ventricle. They were able to trace fibers from Hb (near ventricle) to the interpeduncular nucleus (IP), however the reproducability was variable. They proposed that contact with the choroid plexus may have removed much of the Mn and introduced the variability in CSF manganese concentration. They then went on to scan the Hb and the IP at 2, 6, and 24 hours after a subcutaneous injection and found that 6hr gave the best signal to noise ratio. They note that the Hb showed the increase before its projections and say that this is evidence of anterograde Mn transport, but I don't entirely agree with making that jump in reasoning since I'm pretty sure a few groups mention that areas closer to CSF/blood tend to light up earlier, regardless of projections. Anyway, this paper introduces the issue of the choroid plexus interfering with ICV injections, something I hadn't accounted for and, apparently, neither did the authors. Things are always more complicated than we want them to be. -DH