Effects of prokinetic agents on contractile responses to electrical field stimulation of isolated guinea pig trachea

We investigated the effects of two prokinetic agents, metoclopramide and ci sapride, on the contractile response of isolated guinea pig tracheal segmen ts exposed to electrical field stimulation (EFS). Tracheal segments were su spended between two platinum electrodes in organ baths. Frequency-response curves were obtained by increasing the frequency of the stimuli on equilibr ated tracheal segments, in a stepwise manner. Metoclopramide potentialed th e EFS-induced contraction of the tracheal; the potentiation was more promin ent at lower stimulation frequencies (less than or equal to 10 Hz). Cisapri de significantly inhibited the electrically stimulated contraction in trach ea strips when the frequency of the stimulus was higher than 10 Hz. In the presence of both metoclopramide and cisapride, there was a potentiation of the contractile response at lower frequencies, and this potentiation was re duced when the frequency was higher than 10 Hz. These results demonstrate t hat metoclopramide enhances and cisapride reduces the airway tonicity elici ted by EFS in isolated guinea pig trachea segments. Further studies are nee ded to verify the effects of these prokinetic agents on EFS-induced contrac tion of isolated guinea pig trachea and to determine the mechanisms involve d.