Chloroethylclonidine is a partial alpha1-adrenoceptor agonist in aorta and caudal arteries of the Wistar Kyoto rat.
The interaction between chloroethylclonidine (N-beta-chloroethyl-N-methylamino-methyl-clonidine) and alpha1-adrenoceptors mediating contraction in Wistar Kyoto rat arteries was examined. In caudal (alpha1A-adrenoceptors) and aorta (alpha1D-adrenoceptors) arteries, chloroethylclonidine (10(-4) M) elicited contraction with different time frames (maximal effect within 4 min in the caudal artery and at 30-45 min in aorta). Phentolamine (10(-6) M) completely prevented chloroethylclonidine-induced contraction in aorta, but partially did so in the caudal artery. Rauwolscine (10(-7) M) partially prevented the chloroethylclonidine contractile effect in both arteries. Chloroethylclonidine attenuated the contractile effect of low concentrations of norepinephrine, however, maximal contraction was observed at catecholamine concentrations above 10(-7) M in the caudal artery and 10(-6) M in the aorta. It is concluded that chloroethylclonidine interacts with caudal alpha1A-adrenoceptors as an irreversible partial agonist, inducing vascular contraction probably due to Ca2+ mobilisation, and with aorta alpha1D-adrenoceptors as a partial agonist, inducing slow-onset muscular contraction.
Departamento de Farmacología y Toxicología, CINVESTAV-IPN, México, DF, Mexico.
R
R
Villalobos-Molina
J J
JJ
López-Guerrero
M
M
Ibarra
D058646:Adrenergic alpha-1 Receptor Agonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000378:metabolism; D003000:Clonidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D018340:Receptors, Adrenergic, alpha-1; D014661:Vasoconstriction / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
C547715:Adra1a protein, rat; C547721:Adra1d protein, rat; D058646:Adrenergic alpha-1 Receptor Agonists; D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D015016:Yohimbine; C051731:chlorethylclonidine; D003000:Clonidine; D010646:Phentolamine