The alpha(1A)-adrenoceptor subtype mediates contraction in rat femoral resistance arteries

In this study, alpha (1)-adrenoceptor subtypes were characterised in rat fe moral resistance arteries mounted on a small vessel myograph. A-61603 was f ound to be more potent than noradrenaline and phenylephrine in these arteri es. Brimonidine (UK 14304) could not evoke any contractile responses and th e sensitivity to noradrenaline and phenylephrine was not affected by (8aR, 12aS, 13aS)-5,8,8 a,9,10,11,12,12 a,13a-decahydro-3-methoxy-12-(ethylsulpho nyl)-6H-isoquino[2, 1-g][1.6]-naphthyridine (RS 79948). ruling out the pres ence of alpha (2)-adrenoceptors. Prazosin. 2-methyl-urapidil and 2 -([2,6-d imethoxyphenoxyethyl]aminomethyl)-1,4-benzodioxane (WB 4101) produced right ward shifts in the sensitivity to noradrenaline, giving pA(2) values of 9.6 , 9.4 and 10.4, respectively, in agreement with the presence of alpha (1A)- adrenoceptors. (8-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4 ,5]decane-7,9-dione (BMY 7378; 1 muM) produced a small shift in the sensiti vity of noradrenaline giving a pK(B) of 7.2. In the presence of 300 nM 5-me thyl-urapidil, sensitivity to noradrenaline was not further shifted by 1 mu M BMY 7378. Responses to noradrenaline were unaffected by the alpha (1B)-ad renoceptor alkylating agent chloroethylclonidine (1 muM) These results sugg est alpha (1A)-adrenoceptors mediate contractile responses to noradrenaline in rat femoral resistance arteries. (C) 2001 Elsevier Science B.V. All rig hts reserved.