Insights into the functional roles of alpha(1)-adrenoceptor subtypes in mouse carotid arteries using knockout mice.
1. alpha(1)-Adrenoceptor (AR) subtypes in mouse carotid arteries were characterised using a combination of agonist/antagonist pharmacology and knockout (KO) mice. 2. Phenylephrine (PE) was most potent in the alpha(1B)-KO (pEC(50)=6.9+/-0.2) followed by control (pEC(50)=6.3+/-0.06) and alpha(1D)-KO (pEC(50)=5.5+/-0.07). Both N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl] methanesulphonamide hydrobromide (A-61603) and 5-hydroxytryptamine (5-HT) were more potent in the alpha(1D)-KO (pEC(50)=7.4+/-0.27 and 7.4+/-0.05, respectively) than the control (pEC(50)=6.9+/-0.09 and 6.9+/-0.08, respectively) and equipotent with the control in the alpha(1B)-KO (pEC(50)=6.7+/-0.07 and 6.8+/-0.04). Maximum responses to PE and A-61603 were reduced in the alpha(1D)-KO compared to control; there was no difference in maximum responses to 5-HT. 3. In control arteries, prazosin and 5-methylurapidil acted competitively with pA(2) of 9.6 and 7.5, respectively. BMY7378 produced antagonism only at the highest concentration used (100 nM; pK(B) 8.3). 4. Prazosin, 5-methylurapidil and BMY7378 acted competitively in alpha(1B)-KO carotid arteries with pA(2) of 10.3, 7.6 and 9.6, respectively. 5. In the alpha(1D)-KO, against PE, 5-methylurapidil produced a pA(2) of 8.1. pK(B) values were calculated for prazosin (10.6) and BMY7378 (7.0). Against A-61603, 5-methylurapidil had a pA(2) of 8.5, prazosin 8.6, while BMY7378 had no effect. 6. In conclusion, the alpha(1B)-KO mediates contraction solely through alpha(1D)-ARs and the alpha(1D)-KO through alpha(1A)-ARs. Extrapolating back to the control from the knockout data suggests that all three subtypes could be involved in the responses, but we propose that the alpha(1D)-AR causes the contractile response and that the role of the alpha(1B)-AR is mainly regulatory.
Deighan
Clare
C
Autonomic Physiology Unit, Division of Neuroscience and Biomedical Systems, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow.
Methven
Laura
L
Naghadeh
Mustafa M
MM
Wokoma
Alexis
A
Macmillan
Joyce
J
Daly
Craig J
CJ
Tanoue
Akito
A
Tsujimoto
Gozoh
G
McGrath
John C
JC
D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D017536:Carotid Artery, Common / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics
D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1