Effects of brain stem lesions on 10-Hz and 2- to 6-Hz rhythms in sympathetic nerve discharge.
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 Kölliker-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.
Zhong
S
S
Department of Pharmacology, Michigan State University, East Lansing 48824-1317.
Barman
S M
SM
Gebber
G L
GL
D000818:Animals; D001794:Blood Pressure; D001933:Brain Stem / Q000502:physiology*; D002415:Cats; D003714:Denervation; D004594:Electrophysiology; D008526:Medulla Oblongata / Q000502:physiology; D010507:Periodicity; D011149:Pons / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*