Almitrine bismesylate modulates the susceptibility of guinea pig pulmonary artery to catecholamines, PGF2 alpha and adenosine.

The action of almitrine bismesylate, a potent ventilatory stimulant drug, was studied on the contractile responses to some putative transmitters of carotid body (dopamine, noradrenaline, PGF2 alpha, adenosine) in segments of guinea pig pulmonary arteries. Almitrine (10 mumol/l) was capable of mitigating the contractions evoked by dopamine (0.3 mmol/l), noradrenaline (1 mumol/l) and PGF2 alpha (10 mumol/l) as well. In vessels precontracted with noradrenaline, almitrine (added to the nutrient solution of vessels before applying noradrenaline) potentiated the adenosine-induced initial contractile response without influencing the methylxanthine-sensitive relaxing effect of this purine nucleoside. In contrast, almitrine antagonized the adenosine-induced contraction when applied under precontracted state of arteries. It is supposed that the results presented here could provide some explanation for the variable action of almitrine on pulmonary circulation. On the other hand, these results could serve as a pharmacological basis for further studies of the almitrine action on isolated carotid bodies.