Central catecholaminergic neurons are involved in expression of the
10-hz rhythm in sympathetic nerve discharge.
Orer, Hakan S., Sheng Zhong, Susan M. Barman, and Gerard L. Gebber.
Departments of Pharmacology & Toxicology and Physiology,
Michigan State University, East Lansing, MI, 48824
APStracts 2:0254R, 1995.
We studied the effects of adrenoceptor agonists and antagonists on
sympathetic nerve discharge (SND) of urethan-anesthetized,
baroreceptor-denervated cats. In cats in which a 10-Hz rhythm
coexisted with irregular 2- to 6-Hz oscillations in SND, intra venous
clonidine, an [alpha]2-adrenoceptor agonist, blocked the 10-Hz rhythm
without affecting power at lower frequencies. In contrast, power at
frequencies <6 Hz was depressed by clonidine in cats in which
the 10-Hz rhythm was absent. These effects were reversed by
intravenous administration of [alpha]2-adrenoceptor antagonists,
idazoxan and rauwolscine. Rauwolscine is devoid of affinity for
imidazoline receptors. Furthermore, in cats untreated with clonidine,
idazoxan and rauwolscine enhanced or induced the 10-Hz rhythm without
affecting power at lower frequencies. Prazosin, an [alpha]1
-adrenoceptor antagonist, selectively blocked the 10-Hz rhythm in SND.
Finally, the 10-Hz rhythm in SND was blocked by microinjection of
clonidine into the rostral or caudal ventrolateral medulla. The
results support the view that central catecholaminergic neurons play
a role in expression of the 10-Hz rhythm in SND.
Received 27 February 1995; accepted in final form 22 August 1995.
APS Manuscript Number R139-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.