results - obtained under urethane anesthesia
Regions that show activation during CMG peak include the Pontine Micturition Center (PMC), the Periaqueductal Gray (PAG) and the Hypothalamus. The PMC is a small center in the hindbrain that we now know activates bladder contractions, whereas the PAG receives neural inputs from the bladder and other brain regions, integrates these signals and activates the PMC. The lateral Hypothalamus (LHA) also project to the PMC and our neuro-urology colleagues have shown optogenetic activation of glutamatergic LHA neurons can cause voiding.
See also the work underway in our Neuro-Urology section, where our colleagues are making tremendous progress in defining the neural pathways that control micturition. See too, their recent publication.
Figure 1 The PMC
Figure 2 The Periaqueductal Gray
Figure 3 The Hypothalamus
Figure 4 Negative activation in the Hippocampus
Figure 5 The same as Figure 4 but showing the data in the form of the echo planar image scans - the actual fMRI data
awake studies
Another component to this project is to conduct these studies in mice that are awake throughout the procedures. Maintaining an awake mouse within an MRI instrument without head motion for sufficient time to provide 4-6 cystometry cycles is very challenging. We have been experimenting with alterations to the Bruker bed in which the mouse is placed to reduce head motion. We require the animal to be in place for about 45 minutes to obtain both anatomical an fMRI scans. Figure 6 shows motion changes in 6 directions for a mouse in place for a full 40 minutes of an EPI scan (This mouse was not undergoing cystometry at the time).
Figure 6. The six possible axes of motion that can be made while in a MRI machine. Less is best with ideally lower than 1mm translation and 1 degree of rotation.
