AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 4 804-R809, Copyright © 1989 by American Physiological Society
Role of the ventral surface of medulla in the generation of Mayer waves
M. A. Haxhiu, E. van Lunteren, E. C. Deal and N. S. Cherniack
Department of Medicine, Case Western Reserve University, Cleveland, Ohio.
The regions adjacent to the ventrolateral medullary surface (VMS) play
critical roles in the regulation of respiratory and cardiovascular
function. Furthermore, these areas seem to be important sites for the
integration of afferent inputs from certain sensory organs and the source
of excitatory inputs to preganglionic sympathetic and parasympathetic
neurons. To determine whether the VMS contributes to the generation of
nonrespiratory-related periodic oscillations of arterial blood pressure
(Mayer waves), excitatory substances, such as N-methyl-D-aspartate (NMDA),
cholinergic agonists, and neuropeptides (substance P, neurokinin A,
neurotensin), were applied topically to the intermediate area of VMS in
anesthetized cats. In addition, the effects of application of lidocaine and
inhibitory substances (benzodiazepines) on Mayer waves were studied. After
application of excitatory substances to the VMS, we observed oscillations
of arterial blood pressure, recurring with a period of 17.8 +/- 10 (SE) s,
which had similar characteristics as the Mayer waves recorded during
hypercapnia or hypoxia. In addition, cyclic changes in phrenic nerve
activity and tracheal tone occurred with the same periodicity as arterial
blood pressure oscillation. Application of lidocaine or benzodiazepines on
the intermediate area of the VMS abolished Mayer waves observed during
hypercapnia, hypoxia, or application of excitatory substances. These
findings show for the first time that the VMS can be considered as one of
several synaptic relays involved in the generation of arterial blood
pressure oscillation, as well as the cyclic changes in phrenic nerve
activity and tracheal smooth muscle tone that occur simultaneously.
