Pharmacological characterization of α-adrenoceptors in the bovine median caudal artery

Pharmacological characterization of α1‐adrenoceptor subtypes in the bovine tail artery

“…The tissue was transported to the laboratory on ice where the median caudal artery was dissected from the tail. Tissue preparation protocol was similar to that described by Hill and Dyer (1997). Dissected artery was placed in a modified Krebs' solution of the following composition (m M ): NaCl, 115.21; KCl 4.70; CaCl 2 , 1.80; MgSO 4 , 1.16; KH 2 PO 4 , 1.18; NaHCO 3 , 22.14; dextrose, 7.88; and 0.03 m M EDTA.…”

“…The artery rings were then washed with fresh Krebs' solution every 10 min for 30 min until the basal tension of 2 g was re‐established. Artery rings were treated with 10 μ M tropolone, 1 μ M cocaine and 10 μ M corticosterone for 15 min, prior to obtaining concentration–response relationships to an α‐adrenoceptor agonist, in order to block catecholamine‐ O ‐methyltransferase, neuronal (uptake 1 ) and tissue (uptake 2 ) uptake, respectively (Furchgott & Garcia, 1968; Levin & Furchgott, 1970; Hill & Dyer, 1997). All concentrations of agonists [norepinephrine (10 n M –0.1 m M ), phenylephrine (10 n M –0.1 m M ) and A61603 (1 n M –0.1 m M )] were added to the bath cumulatively in half‐log increments.…”

“…Shifts in agonist EC 30 values by antagonists were used to calculate antagonist potencies (Schild, 1949). For every experiment a tissue not exposed to an antagonist was carried through the procedure to permit corrections for time‐dependent changes in the response of the tissues to the agonist and not because of the antagonist, as recommended by Furchgott (1972) and as used in our laboratory (Zhang & Dyer, 1990; Hill & Dyer, 1997).…”

“…The role of α 1 ‐adrenoceptors has been extensively studied (reviewed in Piascik & Perez, 2001) and their presence in vasculature has been reported in a variety of species such as rat (Lachnit et al ., 1996; Villalobos‐Molina & Ibarra, 1996; Zhu et al ., 1997; Stassen et al ., 1998; Faber et al ., 2001), rabbit (Fagura et al ., 1997), cattle (Hill & Dyer, 1997), sheep (Hu & Dyer, 1997) and human (Jarajapu et al ., 2001).…”

“…Adrenergic agonists induced contractile responses in the isolated bovine tail artery were investigated by Hill and Dyer (1997). They reported that norepinephrine and phenylephrine caused contractions of the isolated bovine tail artery which were significantly inhibited by prazosin, an α 1 ‐adrenoceptor antagonist.…”