Influence of Bay k 8644 on pressor effects of B-HT 920 and cirazoline in pithed cats.
We studied interactions between the putative calcium entry promotor Bay k 8644 and alpha 1-adrenoceptor-mediated increases in diastolic pressure elicited by cirazoline as well as alpha 2-adrenoceptor-mediated pressor responses induced by B-HT 920 in pithed cats. Bay k 8644 (0.01-1 mg/kg, i.a.) did not affect the log dose-pressor response curve of cirazoline, but slightly potentiated the increase in diastolic pressure elicited by B-HT 920. After attenuation of the B-HT 920-induced pressor effects by the calcium entry blocker nifedipine (0.1 mg/kg, i.a.), Bay k 8644 (0.1 mg/kg, i.a.) strongly enhanced the pressor response. The increase in diastolic pressure elicited by cirazoline was not affected by nifedipine (0.1 mg/kg, i.a.), and the addition of Bay k 8644 (0.1 mg/kg, i.a.) had no effect. We conclude that in contrast to the increase in diastolic pressure elicited by B-HT 920, calcium channels are not involved in the cirazoline-induced pressor responses in the pithed cat. The activation of the calcium channels by B-HT 920 is already so efficient that it cannot be further enhanced by Bay k 8644.
Wilffert
B
B
Mathy
M J
MJ
de Jonge
A
A
Thoolen
M J
MJ
Timmermans
P B
PB
van Zwieten
P A
PA
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002415:Cats; D003655:Decerebrate State; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D001381:Azepines; D007093:Imidazoles; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C024763:talipexole; D009543:Nifedipine; C014282:cirazoline; D002118:Calcium