Splanchnic nerve response to A5 area stimulation in rats.
Microinjection of the excitatory amino acid N-methyl-D-aspartate (NMDA, 0.5 nmol) into ventrolateral pons (the A5 area) of halothane-anesthetized, paralyzed rats increased splanchnic (sSND) and renal sympathetic nerve discharges (approximately 45%) and usually decreased lumbar SND. These effects were accompanied by 1) regionally specific changes in vascular resistances, 2) an increase in the gain of the sympathetic baroreflex, and 3) modest reductions in blood pressure and heart rate. sSND activation was greatest when NMDA injections were made in the vicinity of A5 noradrenergic (NE) cells. Injection of 6-hydroxydopamine (6-OH-DA) into A5 area (after 15 days) destroyed 83% of NE neurons and reduced NMDA activation of sSND by 76%. Stimulation of sSND by NMDA in A5 area was reduced 1) 1-2 h after bilateral intraspinal injection of 6-OHDA, but not vehicle or 5,7-dihydroxytryptamine, and 2) by administration of prazosin [alpha 1-NE receptor antagonist, 1 mg/kg iv or 10-20 micrograms intrathecal (it)], but not by idazoxan (alpha 2-NE receptor antagonist, 10-20 micrograms it) or propranolol (0.2 mg/kg iv). We conclude that A5 NE cells have a visceral vasomotor sympathoexcitatory function mediated in large part by their spinal projection.
Huangfu
D
D
Department of Pharmacology, University of Virginia Health Sciences Center, Charlottesville 22908.
Hwang
L J
LJ
Riley
T A
TA
Guyenet
P G
PG
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D007267:Injections; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D011149:Pons / Q000166:cytology / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000502:physiology; D013153:Splanchnic Nerves / Q000502:physiology*; D013268:Stimulation, Chemical; D013564:Sympathetic Nervous System / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology
D016202:N-Methylaspartate; D009638:Norepinephrine