Figure 4.

Double-labeled neurons showing black c-Fos nuclei and brown tyrosine hydroxylase-expressing (TH) neurons in medullary sections from (a) L-proline-injected rats, and (b) negative control, ACSF-injected rats. Arrows indicate double-stained TH neurons, and arrowheads alone indicate TH neurons without c-Fos expression, as shown in the magnified photographs. The framed regions in the small photographs (A1/C1 group) are shown magnified to the right. AP: area postrema, cc: central canal, Gr: gracile nucleus, py: pyramidal tract, Sol: nucleus solitary tract, sp5: spinal trigeminal tract, and Sp5: spinal trigeminal nucleus.