[Effect of nifedipine on perfusion pressure changes produced by alpha 1 adrenergic agonists and depolarizing solution in rat hindlimbs].
The calcium channels blocker, nifedipine (NIF) inhibited in a partial non competitive manner the changes in perfusion pressure (delta P) caused by noradrenaline (NA) in the rat hindquarters, being the maximum inhibition of 31.0 +/- 8.3% (n = 5) for NIF 1.10(-5) M. The vasoconstrictor response of K+ 80 mM - phentolamine 3.10(-6)M was inhibited with lower concentrations of NIF than the one produced by phenylephrine (F) 1.10(-4)M. When the hindquarters were perfused with Krebs OCa-EGTA 2 mM NA developed contractile response. The administration of Ca 2.5 mM after the intracellular calcium store had been depleted, generated vasoconstriction in the presence of F 1.10(-4)M and K+ 80 mM - phentolamine 3.10(-6)M which were blocked in a 60.4 +/- 5.7 (n = 12) and 91.1 +/- 2.3% (n = 10) respectively by NIF 1.10(-5)M. The results suggest that the activation of the adrenergic receptor by NA in the perfused rat hindquarters, probably releases calcium from intracellular stores and promotes calcium influx through pathway scarcely sensitive to NIF. Both mechanisms would be responsible for the partial blockade found in our results.
Consolini
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A
Area Diseño de Fármacos, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina.
Grand
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C
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007552:Isotonic Solutions; D009126:Muscle Relaxation / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000037:antagonists & inhibitors*; D010477:Perfusion; D010646:Phentolamine / Q000037:antagonists & inhibitors*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014661:Vasoconstriction / Q000187:drug effects
D007552:Isotonic Solutions; C051865:Krebs-Ringer solution; D009543:Nifedipine; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D010646:Phentolamine
Effecto de la nifedipina sobre los cambios en la presión de perfusión producidos por agonistas alpha 1 adrenérgicos y solución despolarizante en el tren posterior de la rata.