Noradrenergic neurons with divergent projections to the motor trigeminal nucleus and the spinal cord: a double retrograde neuronal labeling study.

Double retrograde axonal tracing was combined with the indirect immunofluorescence antibody method to determine whether noradrenergic neurons have divergent projections to the motor nucleus of the trigeminal nerve and the spinal cord. Rhodamine-labeled microspheres were injected into the motor trigeminal nucleus and True Blue was deposited into lumbar segments of the spinal cord. After a 10-18-day survival period, brainstem sections were processed for immunofluorescence staining of noradrenergic neurons using antibodies to rat dopamine-beta-hydroxylase. Rhodamine-labeled noradrenergic neurons were observed ipsilaterally throughout the A5 and A7 groups; the contralateral A5 and A7 groups contained few rhodamine-labeled cells. A few rhodamine-labeled noradrenergic neurons were observed in the locus coeruleus and subcoeruleus. True Blue-labeled noradrenergic neurons were identified in the A5 and A7 groups, in the ventral part of the locus coeruleus and in the subcoeruleus. Double retrogradely labeled noradrenergic neurons were observed in the A5 and A7 groups but not in the locus coeruleus and subcoeruleus. Of the total number of rhodamine-labeled noradrenergic cells, a large percentage also contained True Blue: 54% in the caudal A5 group, 59% in the rostral A5 group, and 72% in the A7 group. Of the total number of True Blue-labeled noradrenergic neurons, the percentage of double retrogradely labeled cells was 33% in the caudal A5 group, 46% in the rostral A5 group, and 56% in the A7 group. The findings of this study provide the first anatomic evidence for the existence of a prominent population of noradrenergic cells in the A5 and A7 groups with divergent projections to the motor trigeminal nucleus and the spinal cord. We propose that this subpopulation of noradrenergic neurons in the A5 and A7 groups influences motoneurons at multiple levels of the neuraxis.

Localization of serotonin- and substance P-like immunofluorescence in the caudal spinal trigeminal nucleus of the rat.

A double immunofluorescence labeling method was used to study the localization of serotonin (5-HT)- and substance P (SP)-like immunoreactivities within neuronal fibers in the caudal spinal trigeminal nucleus of the rat. The 5-HT- and SP-immunoreactive fibers share extensive topographical overlap within the superficial laminae of the caudal trigeminal nucleus; however, the majority of stained fibers are immunoreactive for either 5-HT or SP, but not both simultaneously. A small population of fibers in which 5-HT and SP are co-localized is present and restricted to the marginal zone as well as the inner and outer layers of the substantia gelatinosa. The results of the present study suggest that fibers containing coexistent 5-HT and SP may be involved in the processing of nociceptive somatic sensation in the medullary dorsal horn of rat.

Presence of chromatographically identified oxytocin in human sensory ganglia.

Oxytocin-like immunoreactivity (IR-OXT) was detected in extracts of human spinal L5 and Gasserian ganglia by a radioimmunoassay (RIA) specific to oxytocin (OXT) and was identified by high-performance liquid chromatography (HPLC). One of the two immunoreactive peaks obtained on HPLC was found to elute at the same position as the OXT standard. The results reveal the presence of chromatographically identified OXT immunoreactivity in human sensory ganglia.

Immunocytochemistry of enkephalin and serotonin distribution in restricted zones of the rostral trigeminal spinal subnuclei: comparisons with subnucleus caudalis.

The spinal trigeminal subnucleus caudalis processes nociceptive input from the head. However, physiological and behavioral studies in monkeys and humans indicate that painful stimuli from the central face and oral cavity also project through trigeminal nuclei rostral to the spinal subnucleus caudalis. Both enkephalin (ENK) and serotonin (5-HT) are present in rostral trigeminal nuclei and these regions receive inputs from the raphe complex. Thus, it appears that elements of pain-modulating circuitry proposed by Basbaum and Fields (Annu. Rev. Neurosci., 7:309-338, 1984) for the spinal and medullary dorsal horn may also exist in this region. In order to begin an exploration of this circuitry, the present study combines the techniques of retrograde transport of HRP from the ventral posteromedial thalamic nucleus (VPM) of the cat's thalamus to label trigeminothalamic relay cells. Secondarily, immunocytochemical techniques are employed to define the distribution patterns of ENK and 5-HT cells and terminals in relationship to both labeled and nonlabeled neurons in each of the subnuclei of the spinal trigeminal nucleus. Trigeminothalamic relay cells were observed in laminae I and II, the magnocellular region, and the interstitial nucleus (IN) of subnucleus caudalis (Vc). ENK was found in axodendritic and axosomatic terminals, together with a population of small fusiform neurons in all these same areas except the magnocellular region. ENK axosomatic contacts innervated approximately 30% of labeled relay cells, chiefly in lamina I and the IN, or small unlabeled neurons in the same area. Serotonin activity occurred principally in lamina I and the IN and was confined almost exclusively to axodendritic terminals. Examination of subnucleus interpolaris (Vi) revealed relay cells distributed throughout the length of the nucleus and increasing in numbers at rostral levels. A rostral extension of the IN was found just ventrolateral to the main body of Vi and contained numerous labeled cells. The distribution of ENK activity was restricted to the ventral part of Vi and the IN and occurred in axodendritic and axosomatic terminals. These latter elements innervated 30-40% of labeled relay cells in Vi, particularly those located in the IN. Cells containing ENK generally resembled the fusiform cells found in Vc and were distributed in ventral Vi and the IN. Some ENK cells were larger, displayed several dendrites, and occurred only in the ventral Vi. Serotonin within Vi and Vc was confined principally to axodendritic terminals.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of neuropeptide Y immunoreactivity in hypothalamic and brainstem nuclei of young and mature spontaneously hypertensive and normotensive Wistar-Kyoto rats.

The concentration of neuropeptide Y immunoreactivity (NPY-ir) was measured in 8 hypothalamic and 5 brainstem nuclei of 6- and 14-week-old spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats. Strain differences were observed in 3 hypothalamic nuclei and age-dependent changes occurred in 3 hypothalamic and 2 brainstem nuclei. In both the ventromedial hypothalamic nucleus and locus coeruleus the observed change in NPY-ir with age in SH rats was significantly different to the change observed in the WKY. These strain- and age-related differences in NPY-ir may be of relevance in the development of hypertension in the SH rat.

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.

Localization of 5-hydroxytryptamine to neurons and endoneurial mast cells in rat sensory ganglia.

5-Hydroxytryptamine (5-HT) localization has been studied in the spinal and trigeminal ganglia of adult rats using immunofluorescence, peroxidase-antiperoxidase immunocytochemistry and [3H] 5-HT uptake radioautography, the latter two at the ultrastructural level. Endoneurial mast cells, identified by alcian blue staining, formed 8 and 14% of all mast cells and neurons in spinal and trigeminal ganglia respectively and had a median diameter of 7.6 microns. Light and electron microscopic immunocytochemistry showed that these mast cells contained 5-HT-like immunoreactivity. Some 75% of them accumulated exogenous [3H]5-HT in vitro. A population of small-diameter neurons, which did not stain with alcian blue, was also labelled with anti-5-HT serum and accumulated [3H]5-HT. The possible roles of 5-HT in sensory ganglia are discussed.