Mediation by 5-HT2 receptors of 5-hydroxytryptamine-induced contractions of human placental vein.
1. In isolated human placental chorionic vein segments, 5-hydroxytryptamine (5-HT; 10(-8) to 5 x 10(-5) M) elicited concentration-dependent contractions with EC50 = 5.5 (5.2-5.7) x 10(-8) M) and Emax = 93.1 +/- 7.3% of 75 mM KCl-induced contraction. 2. The agonist of 5-HT2 receptors, alpha-methyl-5-hydroxytryptamine, and the selective agonist of 5-HT1 receptors, N,N-dipropyl-5-carboxamidotryptamine and 5-carboxamidotryptamine, induced pronounced concentration-related contractions, which reached 71.1 +/- 6.0%, 53.0 +/- 5.0% and 75.0 +/- 7.8% at the highest dose tested, respectively. The agonist of 5-HT3 receptor, 2-methyl-5-hydroxytryptamine, reached a maximum averaging 36.7 +/- 5.1% of the maximal response to KCl. 3. The 5-HT1 and 5-HT3 receptor antagonists, methiothepin and metoclopramide (10(-7) to 10(-6) M) did not alter the response to 5-HT. However, ketanserin (10(-7) to 10(-6) M), a 5-HT2 receptor antagonist, induced significant inhibition of the concentration-response curve to 5-HT. 4. Contractile responses to 5-carboxamidotryptamine and 2-methyl-5-hydroxytryptamine were not affected by methiothepin and metoclopramide, respectively, whereas ketanserin significantly attenuated the contractile response to these agonists. 5. In conclusions, our study shows that 5-HT2 receptors mediate contraction of the human placental vein with no obvious role for 5-HT1-like, or 5-HT3 receptors.
Cruz
M A
MA
Departamento de Fisiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Chile.
Gallardo
V
V
Miguel
P
P
Carrasco
G
G
González
C
C
D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D010920:Placenta / Q000098:blood supply*; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D014471:Umbilical Veins / Q000187:drug effects* / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects*
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C045918:2-methyl-5-HT; C047087:5-carboxamidotryptamine