Current Project - Labeling of Hypoglossal Motor Nuclei Using Retrograde Dyes
As of October 2012, the Bailey Lab resumed the hypoglossal MN labeling project. The experiment currently entails the injection a fluorescent dye into the genioglossus (an extrinsic protrusor muscle of the tongue), where the dye is able to travel retrogradely through the axons of the innervating motor neurons - in this case those of the hypoglossal nerve (XII cranial nerve). The soma, or bodies of these neurons lie in the hypoglossal motor nucleus (HMN) of the caudal medulla. These soma will give off a bright fluorescent "glow" when labeled correctly and observed using a fluorescent microscope (see image to the right). This procedure has been shown to be useful in studying the anatomical organization of the HMN and as to which muscles different parts of the nucleus innervate.
Future plans for this project involve the use an additional dye to be injected into an intrinsic muscle of the tongue (most likely the superior longitudinalis) and comparison of the anatomical position of the innervating neurons to those that innervate the genioglossus. A further element to be added is the use of the patch-clamp technique on labeled neuron cells. As these cells can be confidently associated with the genioglossus (or any other muscle which has received the injection), a patch-clamp recording of their specific firing properties may provide insight into how the muscle is controlled.
Labeling observed in the caudal slice of the HMN in a P3 rat (Dye: Rhodamine Dextran)
Diagram of slice obtained from rat medulla (red box is area viewed by pictures)