| Abstract: | ![]()
The bronchodilator effects of vasoactive intestinal peptide (VIP) and adenosine triphosphate (ATP), putative neurotransmitters of nonadrenergic, noncholinergic innervation, were compared with those of isoproterenol (ISP) in guinea pig airways by in vivo and in vitro techniques. In both studies, the test agents produced dose-dependent relaxations. The response of airway smooth muscle to ISP was significantly greater than the responses to the test agents. In the in vivo studies, the test agents produced statistically equieffective responses. However, in the in vitro studies, VIP produced complete relaxation of the precontracted tissues to the baseline, whereas ATP could not, suggesting VIP as a more effective relaxant than ATP. |
