AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 6 1015-R1024, Copyright © 1992 by American Physiological Society
Effects of brain stem lesions on 10-Hz and 2- to 6-Hz rhythms in sympathetic nerve discharge
S. Zhong, S. M. Barman and G. L. Gebber
Department of Pharmacology, Michigan State University, East Lansing 48824-1317.
We studied the effects of brain stem lesions or transection on the 10-Hz
and 2- to 6-Hz rhythms in sympathetic nerve discharge (SND) in
baroreceptor-denervated unanesthetized decerebrate cats. The results
indicate that these two rhythms depend in part on different brain stem
regions. The 10-Hz rhythm was eliminated by ablation of the rostral
ventrolateral medulla (RVLM), medullary raphe complex, or pontine
parabrachial and Kolliker-Fuse complex (PB/KF) or by pontomedullary border
transection. Except for RVLM lesions, these procedures did not disrupt the
2- to 6-Hz rhythm in SND. In fact the power in SND at frequencies less than
6 Hz was increased by raphe or PB/KF lesions. Total power in SND was not
significantly affected by raphe or PB/KF lesions, but mean arterial
pressure was significantly reduced. Field potentials recorded from the RVLM
(11 of 26 sites) and raphe (10 of 20 sites) were correlated to the 10-Hz
rhythm in SND, further supporting a role of these areas in either
generating or relaying this rhythm to sympathetic nerves. In contrast,
field potentials recorded from the PB/KF were not correlated to the 10-Hz
rhythm in SND. Thus this region may provide a tonic drive to the 10-Hz
generator located elsewhere in the brain stem.
