title: Role of serotonergic neurons in the maintenance of the 10-Hz rhythm in sympathetic nerve discharge.
abstract: 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, which inhibit the firing of serotonergic medullary raphe neurons, decreased the power in the 10-Hz band of SND without affecting the power at frequencies < or = 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. 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 increased peak frequency and power in the 10-Hz band of SND. Microinjection of N-methyl-D-aspartic acid 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.
authors.affiliation: Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
authors.forename: H S
authors.initials: HS
authors.lastname: Orer
authors.forename: M E
authors.initials: ME
authors.lastname: Clement
authors.forename: S M
authors.initials: SM
authors.lastname: Barman
authors.forename: S
authors.initials: S
authors.lastname: Zhong
authors.forename: G L
authors.initials: GL
authors.lastname: Gebber
authors.forename: R B
authors.initials: RB
authors.lastname: McCall
mesh_terms: D000818:Animals; D002415:Cats; D003714:Denervation; D004594:Electrophysiology; D008526:Medulla Oblongata; D009474:Neurons / Q000502:physiology*; D010507:Periodicity; D011311:Pressoreceptors / Q000502:physiology; D011903:Raphe Nuclei / Q000166:cytology / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
chemical_list: D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin