Figure 5.
Nerve-injury-triggered expression of the transneuronal tracer WGA in myelinated sensory neurons of the mouse results in transneuronal labeling of spinal PKCγ interneurons.
A
, Before injury, WGA (red) is expressed at very low levels in DRG neurons of the ZW2 transgenic mouse.
B
, Axotomy induces expression of WGA in large number of sensory neurons, ipsilateral to the injury.
C
, Most of the WGA-immunoreactive neurons are myelinated (i.e., are N52 positive; yellow).
D
, Consistent with the central projection of myelinated DRG neurons, the WGA-positive terminals (red) are concentrated in the medial regions of the deep laminae of the dorsal horn. However, the WGA immunostaining also overlapped extensively with the band of PKCγ interneurons (green) in lamina IIi.
E
,
F
, Higher magnification of the white boxes in
D
shows that some of these PKCγ interneurons contain the WGA tracer (arrows), indicating that they are directly postsynaptic to myelinated primary afferent fibers. Note that some of the scattered PKCγ interneurons in both laminae I (arrow in
D
) and IIi also receive inputs from myelinated sensory neurons. Scale bar: (in
F
)
A–D
, 100 μm;
E
,
F
, 6.25 μm.