Cardiovascular effects of the 5-HT1A receptor ligand, MDL 73005EF, in conscious spontaneously hypertensive rats.
The effects of pretreatment with the potent and selective 5-HT1A receptor ligand, MDL 73005EF, on the cardiovascular responses to administration of the 5-HT1A receptor agonists, 8-hydroxy-2-(di-n- propylamino)tetralin (8-OH-DPAT), flesinoxan and 5-methylurapidil were studied in conscious spontaneously hypertensive rats (SHR) and compared with those of putative 5-HT1A receptor antagonists. MDL 7300EF (0.1-3 mg/kg) induced a dose-dependent but transient decrease in mean arterial pressure (MAP). Pretreatment with doses of 1 or 3 mg/kg MDL 73005EF significantly inhibited the hypotensive and bradycardiac effects of 8-OH-DPAT (0.03-1 mg/kg). Pretreatment with 1 mg/kg MDL 73005EF similarly reduced the hypotensive actions of flesinoxan (0.3-1 mg/kg) and 5-methylurapidil (0.1 mg/kg). In contrast, MDL 73005EF did not significantly affect the decrease in blood pressure induced by administration of 0.01 mg/kg clonidine, 0.3 mg/kg hydralazine or 0.2 mg/kg nifedipine. The effect of 8-OH-DPAT (0.1 mg/kg) on MAP was also reduced by pretreatment with 1 mg/kg BMY 7378, buspirone or pindolol, but not NAN 190 or spiperone. BMY 7378, NAN 190, pindolol and spiperone induced a significant decrease in blood pressure. To rule out the possibility that the reduced baseline may have influenced responses to 8-OH-DPAT, we showed that pretreatment with the vasodilator, hydralazine (0.3 mg/kg), had no effect on the MAP response to 8-OH-DPAT although it significantly reduced MAP. We conclude that MDL 73005EF acts as a mixed agonist/antagonist at 5-HT1A receptors since it caused a decrease in blood pressure, but also reduced the cardiovascular responses to the 5-HT1A receptor agonists, 8-OH-DPAT, flesinoxan and 5-methylurapidil.
Buisson-Defferier
S
S
Marion Merrell Dow Research Institute, Strasbourg, France.
Van den Buuse
M
M
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D002065:Buspirone / Q000494:pharmacology; D004147:Dioxins / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D010869:Pindolol / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013141:Spiro Compounds / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000959:Antihypertensive Agents; D004147:Dioxins; D010879:Piperazines; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D013141:Spiro Compounds; D014665:Vasodilator Agents; C063249:binospirone mesylate; C057446:5-methylurapidil; C056895:flesinoxan; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D010869:Pindolol; C053428:BMY 7378; D002065:Buspirone