The role of serotonergic neurons in the maintenance of the 10-hz
rhythm in sympathetic nerve discharge.
Orer, Hakan S., Mark E. Clement, Susan M. Barman, Sheng Zhong, Gerard
L. Gebber, and Robert B. McCall.
Department of Pharmacology and Toxicology, Michigan State
University, East Lansing, Michigan 48824 and Cardiovascular
Pharmacology, The Upjohn Company, Kalamazoo, Michigan 49001
APStracts 2:0223R, 1995.
We studied the effects of serotonin (5-HT) receptor agonists and
antagonists on the naturally occurring 10-Hz rhythm in sympathetic
nerve discharge (SND) of urethan-anesthetized, baroreceptor
-denervated cats. Intravenous doses of the 5-HT1A receptor agonists 8
-hydroxy-2-(di-n-propylamino)tetralin (8-OH DPAT) and U-93385E that
inhibit the firing of serotonergic medullary raphe neurons, decreased
the power in the 10-Hz band of SND without affecting the power at
frequencies <6 Hz. The inhibitory effects of 8-OH DPAT and U
-93385E were reversed by the 5-HT1A receptor antagonists spiperone and
WAY 100135. Microinjection of 8-OH DPAT into medullary raphe nuclei
also selectively eliminated the 10-Hz rhythm in SND. The intravenous
administration of the 5-HT2 receptor antagonist methysergide blocked
the 10-Hz rhythm in SND, whereas the 5-HT2 receptor agonist 1-(2,5
-dimethoxy-4-iodophenyl)-2-amino-propane (DOI) increased peak
frequency and power in the 10-Hz band of SND. Microinjection of N
-methyl -D-aspartic acid (NMDA) into the medullary raphe also enhanced
the 10-Hz rhythm in SND. These data support the view that the
naturally occurring discharges of serotonergic medullary raphe
neurons preferentially enhance the 10-Hz rhythm in SND.
Received 15 March 1995; accepted in final form 27 July 1995.
APS Manuscript Number R169-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.