The Ventrolateral Medulla and Sympathetic Regulation of Arterial Pressure

Ann M. Schreihofer and Alan F. Sved (pgs. 78-82)

The ventrolateral medulla is a defined region of the brainstem currently thought to be responsible for sympathetic control of cardiovascular function.  Contained within the ventrolateral medulla are neuronal longitudinal columns that are organized into function zones deemed as pressor or depressor regions corresponding to the effect they have on autonomic cardiovascular function. The neurons in these functional zones can expand from the rostral most point at the ponto-medullary junction caudally to the spinal cord. The most studied region in the ventolateral medulla was named the rostral ventrolateral medulla (RVLM), however there are many other important regions such as the caudal ventrolateral medulla (CVLM), the caudal pressor area, and the medullo-cervical pressor area. The pressor regions, particularly the RVLM, cause vasoconstriction of arterial vessels within the body.  Where as depressor regions inhibit pressor regions in response to the baro-reflex, with a final result of a decrease in vasoconstriction.  Glutamate is the main neurotransmitter released within the pressor areas that contain bulbospinal catecholaminergic neurons, non-catecholaminergic neurons, and A1 neurons. Another common neurotransmitter in the ventrolateral medulla is gamma-Aminobutyric acid referred to as GABA.  GABAergic neurons make up the depressor regions of the ventrolateral medulla, primarily the CVLM. It is the active combination of the pressor and depressor neurons in functional zones of the ventrolateral medulla, that regulate sympathetic control of the cardiovascular system.

-JAI