Spinomesencephalic tract: Projections from the lumbosacral spinal cord of the rat, cat, and monkey

Abstract

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase was used to determine the terminal domain of the projection from the lumbosacral spinal cord to the midbrain in the rat, cat, and monkey. Results have shown that several midbrain regions receiving afferent input from this level of the spinal cord are common to the three species examined. Structures innervated by this projection were located throughout the full rostrocaudal extent of the midbrain. The strongest projections were to the intercollicular region and caudal midbrain contralateral to injection sites in the spinal cord. Terminal labeling in the rostral midbrain, except that observed in the nucleus of Darkschewitsch, was substantially less than that observed at more caudal midbrain levels. Structures receiving the strongest input from the spinal cord included the central gray, nucleus cuneiformis, the deep and intermediate layers of the superior colliculus, and the intercollicular nucleus. Other structures receiving afferent input from the lumbosacral spinal cord included the anterior and posterior pretectal nuclei, red nucleus, Edinger-Westphal nucleus, interstitial nucleus of Cajal, and the mesencephalic reticular formation. It is concluded that the spinal projection to the midbrain is a multicomponent projection consisting of several pathways terminating in discrete midbrain regions. Considering the diverse functions associated with midbrain regions receiving spinal input and the response and receptive field properties of cells belonging to this pathway, the results of the present study are discussed in relation to the potential role of the spinomesencephalic tract in somatic, visceral, and motor function.

Isolating the Modulatory Effect of Expectation on Pain Transmission: A Functional Magnetic Resonance Imaging Study

“…The region of the nCF is a possible site of convergence of descending and ascending influences on pain, because, like the dorsal horn, it participates in both ascending transmission and in modulatory control of nociceptive input. nCF receives a massive afferent input from presumed nociceptive lamina I dorsal horn neurons (McMahon and Wall, 1985;Wiberg et al, 1987;Yezierski, 1988). In addition, nCF has cytoarchitecture similar to the PAG and projects directly to the rostral ventral medulla (RVM), which exerts direct bidirectional control of dorsal horn nociceptive neurons (Zambreanu et al, 2005;Fields et al, 2006).…”

On the Role of the Pedunculopontine Nucleus and Mesencephalic Reticular Formation in Locomotion in Nonhuman Primates

“…Passive response of PPN neurons were also reported in decerebrated preparations and were suggested to receive spino-reticular input (Garcia-Rill and Skinner, 1988). Indeed, in primate, the spino-mesencephalic tractus and part of the spinoreticular tractus were found to reach different sites in the brainstem, including the caudal mesencephalon (Wiberg et al, 1987;Yezierski, 1988;Craig, 1995). Another origin of this passive response could be related to the close proximity with the SCP (Hazrati and Parent, 1992), which conveys information from the deep cerebellar nuclei, which is considered to be another locomotor center (Mori et al, 1999).…”

Role of the Midbrain Periaqueductal Gray in Maternal Nurturance and Aggression:c-fosand Electrolytic Lesion Studies in Lactating Rats

“…This information diverges before or within the midbrain, because lesions of the PP nucleus disrupt suckling-induced oxytocin release but not kyphosis (Hansen and Köhler, 1984;DuBoisDauphin et al, 1985b;Hansen and Ferreira, 1986a;Factor et al, 1993). The spinomesencephalic tract transmits impulses from dorsal horn lamina I through the ascending dorsolateral columns of the spinal cord to synapse onto the cPAG l,vl , particularly at intercollicular levels (Swett et al, 1985;Yezierski, 1988), thereby possibly transmitting afferents from suckling as well as other somatosensory stimuli (Yezierski and Schwartz, 1986).…”