Descending Projections from the Paraventricular Hypothalamic Nucleus to the Spinal Cord: Anterograde Tracing Study in the Rat

Abstract

We investigated the direct projections from the paraventricular hypothalamic nucleus (PVH) to the spinal cord. When Phaseolus vulgaris leucoagglutinin (PHA-L) was injected into the PVH, labeled descending fibers were observed running bilaterally through three pathways. The first pathway ran into the dorsal longitudinal fasciculus and projected to the central gray matter, Edinger-Westphal nucleus, pedunculopontine tegmental nucleus, nucleus of the locus ceruleus and parabrachial nucleus. The second and third pathways coursed through the medial forebrain bundle, ventral tegmental area, and ventral part of the medulla oblongata. At the medulla oblongata, the second pathway curved dorsolaterally and joined Rexed's lamina V of C1 after giving many projections to the nucleus ambiguus, nucleus of the solitary tract, dorsal motor nucleus of the vagus, and a few to the area postrema. The fibers descended through lamina V until C5, and coursed through lamina I from C6 to the upper coccygeal segments. They gave collateral projections to lamina I from the cervical through the upper coccygeal segments. The third pathway coursed laterally and descended through the lateral funiculus after giving projections to the lateral reticular nucleus and the marginal layer of the spinal trigeminal nucleus. These fibers gave off many projections to the intermediolateral cell column of the thoracic cord and the sacral parasympathetic nucleus. Lamina X received many projections from the fibers of the lateral funiculus at C5 through the b-segment of sacral spinal cord. These results indicate that the PVH may integrate directly with the medullary and spinal autonomic regulatory nuclei, including the vagus complex, sympathetic intermediolateral cell column, laminae I and X, and sacral parasympathetic nucleus.

Suprachiasmatic nucleus input to autonomic circuits identified by retrograde transsynaptic transport of pseudorabies virus from the eye

“…Once preganglionic nuclei are infected, higher-order CNS neurons that target the infected nuclei and regulate autonomic outflow are in turn transsynaptically infected. For example, the PVN projects bilaterally, although predominately ipsilaterally, to the IML, EW, and SSN (Saper et al, 1976;Swanson, 1977;Luiten et al, 1985;Hosoya et al, 1990;Zheng et al, 1995;Vrang et al, 1997) and bilateral, although predominately ipsilateral, label was noted in the PVN in the present study. Moreover, the results from the lesions suggest that neurons in the PVN may have been retrogradely labeled from all three preganglionic autonomic nuclei in the present study.…”

“…This could represent either a species difference, or it is possible that the EW lesions in the hamster disrupted descending hypothalamic efferent fibers destined to the IML (Morin et al, 1994) and thus eliminated retrograde transport to the hypothalamic SCN. However, the route taken by descending PVN projections to the spinal cord appear similar in the rat and hamster (Youngstrom and Nunez, 1992;Zheng et al, 1995;Toth et al, 1999a), suggesting that the EW lesions would have had a similar effect in both species.…”

Alcohol-Induced c-Fos Expression in the Edinger-Westphal Nucleus: Pharmacological and Signal Transduction Mechanisms

“…Physiological as well as morphological data suggest that EW neurons are influenced by an inhibitory input from the hypothalamus (Saper et al, 1976;Koss, 1986;Zheng et al, 1995). Although the transmitter systems targeted herein do not address this notion, the existence of Neuropeptide Y Y5 receptors in the EW gives credence to this hypothesis (Grove et al, 2000).…”

Autonomic Consequences of Spinal Cord Injury

“…Immunolabeling indicates serotonergic axons from caudal raphe nuclei innervate spinal autonomic regions, as well as catecholaminergic axons derived from the locus coeruleus, subcoeruleus and A5 (41,75,76,246,254). Anterograde neuronal tract tracing reveals PVN neurons extending axons to lumbosacral SPNs and sacral PPNs in the spinal cord (139,284,388). Currently, it is unknown how these nuclei are connected to each other to coordinate urinary activity.…”