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Direct projection from the hypothalamic paraventricular nucleus to the sympathetic preganglionic neurons in the rat, revealed by a combination of anterograde and retrograde labeling techniques
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DIRECT PROJECTION FROM THE HYPOTHALAMIC PARAVENTRICLJLAR NUCLEUS TO THE SYMPATHETIC PREGANGLIONIC NEURONS IN THE RAT, REVEALED BY A COMBINATION OF ANTEROGRADE AND RETROGRADE LABELING TECHNIQUES. YASUHIKO HOSOYA, Department of Anatomy, Institute of Basic Medical Sciences, University of Tsukuha, Tsukuha, Iharaki-305, Japan The descending projections from the hypothalamic paraventricular nucleus (PVN) to the sympathetic preganglionic neurons (SPN) were studied by the tract-tracing methods in the thoracic cord of the rat. PHA-L was injected iontophoretically to the PVNs of both sides and a small amount of aqueous solution of 1% cholera toxin subunit B (CTh) or 25% HRP was injected bilaterally into the superior cervical ganglia in the same animal. Using different chromogens, two kinds of tracers (PHA-L and CTb) were discriminated immunohistochemically. Although many PVN fibers were ohservcd in the intermediolateral nucleus, only a few labeled fibers were in apposition to the dendrites of the SPNs. On the other hand, the dendrites of some SPNs in the intercalated and central autonomic nuclei were studded with varicosities of PVN fibers. The electron microscopic examination showed that varicosities of PVN fibers make synaptic contacts with the dendrites of SPNs. The results of the present study indicate that the PVN exerts directly on the activities of the SPNs through its descending path.
5-28
DIRECT PROJECTION FROM THE HYPOTHALAMIC PARAVENTRICLJLAR NUCLEUS TO THE SYMPATHETIC PREGANGLIONIC NEURONS IN THE RAT, REVEALED BY A COMBINATION OF ANTEROGRADE AND RETROGRADE LABELING TECHNIQUES. YASUHIKO HOSOYA, Department of Anatomy, Institute of Basic Medical Sciences, University of Tsukuha, Tsukuha, Iharaki-305, Japan The descending projections from the hypothalamic paraventricular nucleus (PVN) to the sympathetic preganglionic neurons (SPN) were studied by the tract-tracing methods in the thoracic cord of the rat. PHA-L was injected iontophoretically to the PVNs of both sides and a small amount of aqueous solution of 1% cholera toxin subunit B (CTh) or 25% HRP was injected bilaterally into the superior cervical ganglia in the same animal. Using different chromogens, two kinds of tracers (PHA-L and CTb) were discriminated immunohistochemically. Although many PVN fibers were ohservcd in the intermediolateral nucleus, only a few labeled fibers were in apposition to the dendrites of the SPNs. On the other hand, the dendrites of some SPNs in the intercalated and central autonomic nuclei were studded with varicosities of PVN fibers. The electron microscopic examination showed that varicosities of PVN fibers make synaptic contacts with the dendrites of SPNs. The results of the present study indicate that the PVN exerts directly on the activities of the SPNs through its descending path.