Fig. 4.

Segmental differences in the responsiveness of the allantoic artery to adrenergic agonists. Contractile effects of the nonselective adrenergic receptor agonist norepinephrine (NE, a), the α₁-adrenergic agonist phenylephrine (Phe, b), and the β-adrenergic agonist isoproterenol (c) in ischiatic, allantoic intraembryonic (proximal and distal) and allantoic extraembryonic arteries from 19-day chicken embryos. For the isoproterenol experiments, vessels were pre-contracted with KCl (62.5 mM). Data points are presented as mean ± SE. Groups without a common letter have a significantly different E _max