Ventrolateral medullary control of cardiovascular activity during muscle contraction

An overview of the role of ventrolateral medulla (VLM) in regulation of car diovascular activity is presented. A summary of VLM anatomy and its functio nal relation to other areas in the central nervous system is described. Ove r the past few years, various studies have investigated the VLM and its inv olvement in cardiovascular regulation during static muscle contraction, a t ype of static exercise as seen, for example, during knee extension or hand- grip exercise. Understanding the neural mechanisms that are responsible for regulation of cardiovascular activity during static muscle contraction is of particular interest since it helps understand circulatory adjustments in response to an increase in physical activity. This review surveys the role of several receptors and neurotransmitters in the VLM that are associated with changes in mean arterial pressure and heart rate during static muscle contraction in anesthetized animals. Possible mechanisms in the VLM that mo dulate cardiovascular changes during static muscle contraction are summariz ed and discussed. Localized administration of an excitatory amino-acid anta gonist into the rostral portion of the VLM (RVLM) attenuates increases in b lood pressure and heart rate during static muscle contraction, whereas its administration into the caudal part of the VLM (CVLM) augments these respon ses. Opioid or 5-HT1A receptor stimulation in the RVLM, but not in the CVLM , attenuates cardiovascular responses to muscle contraction. Furthermore, i ntravenous, intracerebroventricular or intracisternal injection of an alpha (2)-adrenoceptor agonist or a cholinesterase inhibitor attenuates increases in blood pressure and heart rate during static muscle contraction. Finally , the possible involvement of endogenous neurotransmitters in the RVLM and the CVLM associated with cardiovascular responses during static muscle cont raction is discussed. An overview of the role of the VLM in the overall car diovascular control network in the brain is presented and critically review ed. (C) 1998 Elsevier Science Ltd. All rights reserved.