Fig. 5.

Cannula placements and local effects of intramedullary microinjection of PGE2. Top, Bright-field photomicrographs of Nissl-stained sections showing cannula placements in the rostral ventrolateral medulla. Magnification, 15×.Bottom, Fluorescence photomicrographs of a single field near a cannula tip in the ventrolateral medulla stained concurrently for GFAP-ir and Fos-ir. Surrounding the area of tissue damage (*) is a region of intense GFAP labeling of reactive astrocytes. At the margin of this zone lies a band of Fos-ir neurons, which we take to be nonspecifically induced as a consequence of microinjection. Beyond this, GFAP labeling tapers precipitously to levels indistinguishable from those seen at a comparable locus on the contralateral side, and Fos-ir is seen in the C1 region of the rostral ventrolateral medulla in rats injected with suprathreshold doses of PGE2. XII, Hypoglossal nucleus; stv, spinal trigeminal tract;SpV, spinal trigeminal nucleus; py, pyramidal tract; IO, inferior olivary complex. Magnification, 150×.