Cardiovascular responses produced by microinjection of serotonin-receptor agonists into the paraventricular nucleus in conscious rats.
Activation of serotonin (5-hydroxytryptamine, 5-HT) receptors in the brain produces cardiovascular responses by altering autonomic outflow. The paraventricular nucleus (PVN) contains a modest density of 5-HT receptors and has connections to autonomic centers. Experiments were designed to determine whether cardiovascular responses were produced by the administration of 5-HT2- and 5-HT1A-receptor agonists into the PVN of conscious rats. The microinjection of the 5-HT2-receptor agonist DOI [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl] into the PVN produced dose-dependent (1-10 nmol) increases in heart rate and blood pressure; the peak responses were +39 +/- 10 beats/min and +6 +/- 2 mm Hg, respectively. Both responses were blocked by the concomitant administration of the selective 5-HT2-receptor antagonist LY53857 into the PVN. By contrast, the microinjection of the selective 5-HT1A-receptor agonist R(+)-8-OH-DPAT [R(+)8-hydroxy-2-(di-n-propylamino) tetralin HBr; 1-10 nmol] into the PVN did not affect blood pressure or heart rate. These data suggest that 5-HT neurons projecting from the raphe nuclei to or near the PVN can participate in the central control of the cardiovascular system by way of 5-HT2 receptors. Apparently 5-HT neurons terminating in the PVN can increase blood pressure and heart rate and produce sympathoadrenal activation, metabolic and hormonal responses consistent with those observed in several different stress paradigms.
Bell
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AA
Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City 66160-7417, USA.
Butz
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BL
Alper
R H
RH
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004873:Ergolines / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects*; D007215:Indophenol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
D004873:Ergolines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C113896:dimethoxy-4-indophenyl-2-aminopropane; D007215:Indophenol; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C032663:LY 53857