부산대학교 도서관

Summary 1 Originally, the so-called `adrenaline hypothesis' related the release of noradrenaline (NA) to stimulation of presynaptic β2 -receptors in nerve endings; now it confers a possible role to adrenaline taken up then released by nerves endings. It represents a potentially useful therapeutic pathway. The present study aims to investigate the effects of formoterol, a highly selective β2 -adrenoceptor agonist. 2 It was carried out in freely moving rats, the isotope dilution technique being used to measure the NA spill over rate (NA-SOR) and metabolic clearance rate (MCR). 3 A series of three results are reported. (a) When compared with adrenaline on equimolar basis, formoterol (2.3 μg kg-1 min-1 ) increased NA-SOR while mean arterial blood pressure was decreased and heart rate increased. Thus, it was difficult to separate a direct presynaptic effect from indirect baroreflex-dependent activation of the sympathetic system. (b) When formoterol was infused at 1 ng kg-1 min-1 , a dose empirically defined to induce no haemodynamic effect, NA-SOR was significantly increased, while NA-MCR remained unchanged. (c) The NA-SOR response to formoterol was not amplified by the presynaptic α2 -adrenoceptor blocker, yohimbine, in contrast to the NA-SOR response to adrenaline. 4 In conclusion, formoterol, a β2 -adrenoceptor agonist, is shown to increase the release and plasma concentration of NA while its clearance was not changed. [ABSTRACT FROM AUTHOR]