Cooperative mediation byserotonin S2and thromboxane A2/prostaglandin H2receptor activation ofcyclic flowvariations indogswith severe coronary artery stenoses
Wehavereported previously that thromboxane A2/prostaglandin (PG)H2 andserotonin independently mediate theoccurrence ofcyclic flowvariations (CFVs) inacanine preparation ofsevere coronary artery narrowing. Thismaybeduetoaneffect ofthese substances onplatelets and/or the vascular wall. Wetested thehypothesis that there isacooperative effect between thromboxane A2/PGH2 andserotonin receptor stimulation inthedevelopment ofCFVsinthis animal preparation. After placement ofahardplastic cylindrical constrictor around theleft anterior descending coronary artery, CFVsdevelop andarecharacterized byrepetitive cycles ofdeclines incoronary blood flowandabrupt increases inflow. Inacontrol group ofdogs, CFVfrequency (cycles/hour) andseverity (lowest coronary blood flow just before its restoration) didnotchange significantly overa3hrinterval. Inasecond group ofdogs, CFVswereestablished after constrictor placement, abolished withtheserotonin (5HT2) receptor antagonist ketanserin, andreestablished bythecontinuous infusion ofserotonin into theleft atrium. Serotonin induced