Projections of the caudal ventrolateral medulla to the thoracic spinal cord in the rat

Abstract

Background: The caudal ventrolateral medulla (CVLM), an area having cardiovascular and respiratory functions, contains neurons that project to the thoracic spinal cord. It has been presumed, although never demonstrated, that the CVLM thoracic projections terminate on intercostal and sympathetic motor neurons. Using a combination of tracers, the purpose of the present study was to describe a route through which the CVLM may directly influence sympathetic and intercostal motor neurons. Methods: To label the medullospinal projections orthogradely, either biotinylated dextran amine or lectin conjugated horseradish peroxidase was injected into the CVLM. To label the intercostal and sympathetic motor neurons retrogradely, cholera toxin subunit B-horseradish peroxi-dase was injected into the intercostal muscles and superior cervical ganglion. Subsequently, projections from the CVLM were observed to terminate on, or in close proximity to, sympathetic and intercostal motor neurons. Results: Projections to sympathetic neurons were largely ipsilateral, whereas projections to intercostal neurons were primarily contralateral. In retrograde labeling experiments, it was observed that many of the CVLM-thoracic projections originated from the nucleus retroambiguus. Conclusions: The finding that the CVLM projects to sympathetic and intercostal motor neurons supports its role in cardiovascular and respiratory functions. The authors suggest that CVLM influences upon sympathetic motor neurons may be inhibitory. Anat. Rec. 250:95-102, 1998.

Projections from the brain to the spinal cord in the mouse

“…Cells of the contralateral RAmb are labeled but the density of labeled cells is much less than that of Amb. This is consistent with reports of studies in cat, rat, and mouse (Hardy et al 1998;Gerrits et al 2000;VanderHorst 2005;Boers et al 2006). …”

Acute systemic hypoxia activates hypothalamic paraventricular nucleus-projecting catecholaminergic neurons in the caudal ventrolateral medulla

“…Pontine groups that play a role in respiratory rhythmogenesis also receive projections from cells in the CVLM (23,25). The CVLM has projections to the thoracic spinal cord that terminate on intercostal, sympathetic preganglionic, and phrenic motor neurons (17,26,73), supporting their involvement in respiratory control. Taken together, these data suggest that CVLM neurons are a heterogeneous population with the ability to influence a variety of other brain regions and physiological responses to hypoxia.…”

Origin and neurochemical properties of bulbospinal neurons projecting to the rat lumbar spinal cord via the medial longitudinal fasciculus and caudal ventrolateral medulla

“…Bulbospinal pathways are known to have monosynaptic actions on motoneurons and premotor interneurons (Grillner and Lund, 1968; Floeter et al, 1993; Gossard et al, 1996; Bannatyne et al, 2003; Jankowska et al, 2003; Riddle et al, 2009; Galea et al, 2010) and they also have profound influences on sensory systems (especially nociceptive pathways), respiration and autonomic activity (Basbaum and Fields, 1979; Hardy et al, 1998; Tavares and Lima, 2002). These pathways form extensive termination patterns within the spinal gray matter.…”

“…They influence a variety of spinal networks including those concerned with motor control, sensory input (including pain) and autonomic function. It is likely that one of the functions of BS systems is to coordinate the activity of spinal networks involved in these various processes (Holstege, 1996; Hardy et al, 1998; Tavares and Lima, 2002). The neurons that give rise to BS pathways project to the spinal cord via fiber tracts in the medulla (Mitani et al, 1988).…”