Kubke Lab:Research/CND/Summary VII

Stage 24

Case nf002

(look at record for staging issues)

Distal end of VII nerve with VIII removed. DiI crystal.

MN labelled unilaterally. There is also a thin lateral fascicle of short afferent axons on the ipsilateral side. Stack does not cover full thickness of hindbrain - I am missing the bundle of axons that are going to the motoneurons in the caudal segment.

The caudal group of motoneurons seem to have extensions on or crossing the floor plate.

Rostral sensory fascicle seems separated into 2 discrete bundles. Caudally it seems to be the case too, but they appear to come back together at a more caudal level (not so for rostral bundles).

Stage 26

Case nf003

Distal VII with VIII removed - DiI crystal

Series 020 (Red, Facial labelling) shows an interesting "loop" of the axons around the nerve entry stump. The caudal branch of the afferent is split in 2. It looks like the more medial of these two is where the axons of the MNs seem to be riding on.The more rostral afferent bundle also seems split in 2 with the more medial half seeming more defasciculated.

Motoneurons: MNs from r5 group seem to hit afferent bundle at more of a right angle and then ride on, rostrally, to get to the exit point, whereas the MNs from r4 segment seem to be going straight towards the brainstem exit point.

case nf005

Distal VII, DiI crystal, bilateral. Colabelling with VIII.

Nerve entry well differentiated from VIII nerve, entering ventromedially to the entry of caudal VIII.

Both rostral and caudal afferent bundles seem to be loosely fasciculated, but do not appear to form separate discrete bundles. There are clear varicosities and "filopodia-like" structures along the axons, but don't see clear collaterals. The rostral bundle seems to be travelling in between the two rostral caudal VIII bundles, and some close apposition between the two types of axons can be seen.

Efferent neurons form a dispersed column. Their axons in r5 course laterally reaching or almost reaching the sensory bundle where they make a sharp turn towards the nerve exit point. Axons from efferents in r4 seem to have their axons coursing directly to the nerve exit point.

There are numerous processes crossing the floor plate.