title: Extracellular serotonin changes in VLM during muscle contraction: effects of 5-HT1A-receptor activation.
abstract: This study determined whether muscle contraction causes an increase in extracellular levels of serotonin (5-HT) in the rostral (rVLM) or caudal ventrolateral medulla (cVLM) in anesthetized rats. Muscle contraction, evoked by tibial nerve stimulation, increased mean arterial blood pressure (MAP) by 27 +/- 4 mmHg (n = 8). In addition, 5-HT levels in the rVLM were elevated by 65 +/- 9% during the contraction (n = 8). Results were similar over two repeated contractions. In contrast, muscle contraction increased MAP, but not 5-HT, levels in the cVLM (n = 6). Tibial nerve stimulation after muscle paralysis had no effect on either MAP or 5-HT levels in both rVLM and cVLM. Microdialysis of a 5-HT1A agonist, 8-OH-DPAT (10 mM), into the rVLM for 30 min (n = 6) blunted the MAP change and reduced 5-HT release during contraction. Administration of NAN-190, a 5-HT1A antagonist, into the rVLM had no effect on 5-HT release and cardiovascular responses during muscle contraction and blocked the changes in 5-HT, MAP, and heart rate to static contraction after subsequent microdialysis of 8-OH-DPAT. Results demonstrate that 5-HT levels in the rVLM increase during muscle contraction and that 5-HT1A-receptor activation in the rVLM blunts MAP response to muscle contraction via a decrease in the extracellular concentration of 5-HT.
authors.affiliation: Department of Pharmacology, College of Osteopathic Medicine, University of New England, Biddeford, Maine 04005, USA.
authors.forename: G
authors.initials: G
authors.lastname: Asmundsson
authors.forename: D
authors.initials: D
authors.lastname: Caringi
authors.forename: D J
authors.initials: DJ
authors.lastname: Mokler
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Ishide
authors.forename: A
authors.initials: A
authors.lastname: Ally
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D017551:Microdialysis; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D010243:Paralysis; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013979:Tibial Nerve / Q000502:physiology*
chemical_list: D010879:Piperazines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin