Morphology and distribution of primary afferent fibres expressing alpha-galactose extended oligosaccharides in the spinal cord and brainstem of the rat. Light microscopy.

The light microscopic morphology and distribution of non-substance P-containing small primary afferent fibres were studied. These fibres were labelled using LD2 and LA4 monoclonal antibodies which recognize alpha-galactose extended oligosaccharides expressed by primary afferent neurons. The LD2 and LA4 antibodies immunostained small primary afferent fibres ending mainly in lamina II of the spinal cord dorsal horn and trigeminal subnucleus caudalis of the rat. The lamination pattern of both types of primary afferents was assessed using an image analysis system. The highest density of LD2-immunoreactive fibres was located in a patchy band located in lamina II outer, while LA4-immunoreactive fibres were distributed mainly through lamina II inner. In lateral regions of cervical and lumbar dorsal horn the LA4-immunoreactive band is broader and comprises almost all lamina II. In contrast to substance P-containing primary afferents, a low density of LD2- or LA4-immunoreactive fibres was found in lamina I, and no terminal fields were found in lamina V or lamina X of the spinal cord or in levels of the trigeminal system outside the subnucleus caudalis. Both antibodies also labelled the parent fibres in the white matter fasciles. LD2-immunoreactive fibres were located in the dorsal roots, medial regions of the Lissauer tract, dorsal columns of the spinal cord, outer regions of the spinal trigeminal tract and dorsal to the cuneatus and gracilis nuclei. In contrast, LA4-immunoreactive fibres were restricted to the dorsal roots, medial and lateral regions of the Lissauer tract and the outer regions of the trigeminal tract. Immunostained fibres in the rootlets of the X and IX nerves and immunoreactive terminal arborizations in various subnuclei of the nucleus tractus solitarius were seen using both antibodies. These results show that subpopulations of small primary afferents stained by LD2 and LA4 antibodies have distinct patterns of central distribution and are consistent with a subdivision of small primary afferents into peptide- and non-peptide-containing groups.

Sources of the catecholaminergic innervation of the trigeminal nucleus caudalis in cat.

Injections of the retrogradely transported fluorescent dye, Evans blue, into the trigeminal nucleus caudalis were combined with the glyoxylic acid histofluorescence technique to determine the sources of catecholamine-containing varicosities innervating nucleus caudalis. Results indicate that the sources of this catecholamine innervation are widespread, originating from cell bodies throughout the brain stem including the medullary catecholamine cell groups as well as the noradrenergic nuclei of the dorsolateral pons, including locus ceruleus, subceruleus, Kölliker-Fuse, and the parabrachial nuclei. A small projection from the presumably dopaminergic neurons of the hypothalamus was also noted. The catecholamine innervation of n. caudalis in the cat is from widespread brain stem sources, a pattern different from the catecholamine innervation of the spinal cord, which receives its major catecholamine input from the Kölliker-Fuse nucleus.