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Catecholaminergic projections from ventrolateral medulla to A5 pontine region: anatomical and electrophysiological studies and a possible involvement in the chemoreflex

Grant number: 13/04689-3
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): August 01, 2013
Effective date (End): November 30, 2015
Field of knowledge:Biological Sciences - Physiology
Principal Investigator:Thiago dos Santos Moreira
Grantee:Thais Leoni Borella
Home Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The baroreceptors, chemoreceptors and cardiopulmonary receptors are important for the central cardiovascular regulation through its projections to the central nervous system (CNS) by IX and X cranial nerves (glossopharyngeal and vagus nerves, respectively). The information from these peripheral receptors may be distributed to different areas of the CNS, among them stand out the areas located in the ventrolateral medulla which control sympathetic tone in the cardiovascular system, as well as areas responsible for respiratory control. At rest conditions, pre-sympathetic neurons of the ventrolateral bulb are the first efferent sympathetic activity, 70% of these neurons synthesize adrenaline and belong by definition, the C1 C1 catecholamine neurons, which are also capable of releasing glutamate as neurotransmitter and other neuropeptides. These neurons area part of the rostral ventrolateral medulla (RVLM) where there are the sympathetic vasomotor neurons. It is clear that these neurons have an important role in controlling blood pressure in rats. More recently studies demonstrated a participation of C1 neurons in the control of respiratory activity and parasympathetic activity involving neurons in the dorsal motor nucleus of the vagus. It suggests that the neurons located in the region C1 are not only involved in cardiovascular control, but acting as a central integrator of autonomic functions. Another important area for cardiorespiratory control is the noradrenergic A5 region, located in the ventrolateral medulla between the facial nerve and the caudal olivary nucleus. The A5 noradrenergic group sends direct projections to the spinal cord and also other areas involved with the bulbar cardiorespiratory control. This region seems to be involved in the control of respiratory rhythm, and connect reciprocally with the NTS and the rostral ventrolateral medulla (RVLM). The noradrenergic neurons located into the A5 area increase or decrease their activity through the activation of the peripheral chemoreflex or baroreflex activation, respectively. The A5 area is the most important area of noradrenergic excitation (approximately 40%) of the sympathetic preganglionic neurons of the spinal cord. It shows that this area is as important as the RVLM for the central sympathetic activity control.The evidence that the catecholaminergic C1 neurons is not the only one which has sympatho-excitatory neurons, it would be important to figure out if the C1 neurons act as integrative center of cardiorespiratory responses through a connection with the A5 pontine region. (AU)