Role of serotonergic input to the ventrolateral medulla in expression of the 10-Hz sympathetic nerve rhythm.
We studied the changes in inferior cardiac sympathetic nerve discharge (SND) produced by unilateral microinjections of 5-hydroxytryptamine (5-HT) receptor agonists and antagonists into the ventrolateral medulla (VLM) of urethane-anesthetized, baroreceptor-denervated cats. Microinjection of the 5-HT2 receptor antagonist LY-53857 (10 mM) into either the rostral or caudal VLM significantly reduced (P < or = 0.05) the 10-Hz rhythmic component of basal SND without affecting its lower-frequency, aperiodic component. The selective depression of 10-Hz power was accompanied by a statistically significant decrease in mean arterial pressure (MAP). Microinjection of LY-53857 into the VLM also attenuated the increase in 10-Hz power that followed tetanic stimulation of depressor sites in the caudal medullary raphé nuclei. Microinjection of the 5-HT2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)2-amino-propane (DOI; 10 microM) into the VLM selectively enhanced 10-Hz SND, and intravenous DOI (1 mg/kg) partially reversed the reduction in 10-Hz SND produced by 5-HT2 receptor blockade in the VLM. Microinjection of the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OHDPAT; 10 mM), into either the rostral or caudal VLM also selectively attenuated 10-Hz SND and significantly reduced MAP. The reduction in 10-Hz SND produced by 8-OHDPAT was partially reversed by intravenous WAY-100635 (1 mg/kg), which selectively blocks 5-HT1A receptors. These results support the view that serotonergic inputs to the VLM play an important role in expression of the 10-Hz rhythm in SND.
Orer
Hakan S
HS
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA.
Gebber
Gerard L
GL
Barman
Susan M
SM
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage / Q000494:pharmacology; D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000502:physiology; D002415:Cats; D003714:Denervation; D004873:Ergolines / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage / Q000494:pharmacology; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology; D044282:Receptor, Serotonin, 5-HT1A / Q000187:drug effects; D012701:Serotonin / Q000502:physiology*; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology*
D000662:Amphetamines; D004873:Ergolines; D018690:Excitatory Amino Acid Agonists; D010879:Piperazines; D011725:Pyridines; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D017366:Serotonin Receptor Agonists; D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin; D016202:N-Methylaspartate; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C032663:LY 53857; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine