VENTROLATERAL MEDULLA AND THE CARDIOVASCULAR CONTROL: NEW EVIDENCE NEW DOUBTS

Abstract

More than 30 years ago a model was proposed trying to explain how the central nervous system controls the cardiovascular adjustments. According to this model the medullary vasomotor nuclei are the main structures involved in the cardiovascular reflex control. It also shows the nucleus tractus solitarius (NTS) as being the first integrative center for the baroceptors afferents and the descending pathways from supramedullary nuclei of hypothalamus, which contribute at defense and alert reactions. The NTS exhibits excitatory projections to the caudal ventral lateral medulla (CVL) which inhibits the rostral ventral lateral medulla (RVL). The RVL is the main source of excitatory inputs to the sympathetic preganglionic neurons, being responsible for the sympathetic tonus to heart and blood vessels. Important projections from CVL to diencephalon structures (Median preoptic nucleus, Hypothalamic paraventricular nucleus, Supraoptic nucleus) also play an important role in the control of the extracellular compartment composition and volume. The gigantocellular depressor area (GiDA) is likely to be another vasomotor center involved in blood flow adjustments through direct projections to Preganglionic Sympathetic Neurons (SPN). How GiDA mediates its vasodepressor effects is unknown. In the last 10 years we have been studying the pathways and neural mechanisms related to muscle and visceral blood flow regulation. Obtained data are not compatible with the proposed model.