Central catecholaminergic neurons are involved in expression of the 10-Hz rhythm in SND.
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, intravenous clonidine, an alpha 2-adrenoceptor agonist, blocked the 10-Hz rhythm without affecting power at lower frequencies. In contrast, power at frequencies < or = 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.
Orer
H S
HS
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
Zhong
S
S
Barman
S M
SM
Gebber
G L
GL
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology; D002415:Cats; D003000:Clonidine / Q000494:pharmacology; D004594:Electrophysiology; D004837:Epinephrine / Q000502:physiology*; D007275:Injections, Intravenous; D008845:Microinjections; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology*; D009991:Oscillometry; D010507:Periodicity; D011224:Prazosin / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D000661:Amphetamine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin; D004837:Epinephrine