Evidence for prejunctionally located β2-adrenoceptors in the cat spleen

The number of β-adrenoceptors in myocardium and spleen from 6-hydroxydopamine (6-OH-DA) treated cats was determined by radioligand binding with [125I]-iodohydroxybenzylpindolol (IHYP). The effectiveness of 6-OH-DA pretreatment was assessed by analyses of the tissue content of catecholamines and the contractile response of isolated splenic strips to electrical stimulation. Since no effect on the splenic strip was produced by the β-agonist isoprenaline, whereas noradrenaline caused contraction, it is concluded that the smooth muscle of the splenic capsule is controlled by postjunctional α-adrenoceptors.