[Comparative vasodilator action of 5 vasodilators: dihydroergotoxine, nicergoline, papaverine, naftidrofuryl and buflomedil on the femoral artery of the dog].

1. Papaverine (PAP), Naftidrofuryl (NAF), Buflomedil (BUF), Nicergoline (NIC) and Dihydroergotoxine (DIT) were injected in the dog iliac artery at increasing doses (25, 100, 400, 1600 micrograms . kg-1) successively at 10 minutes intervals and the femoral blood flow was measured with an electromagnetic flowmeter. The same volume of saline was injected in the contralateral iliac artery. Heart rate and radial artery pressure were measured and the femoral resistances computed. Noradrenaline (2 microgram . kg-1) was injected before and after the highest dose of vasodilators. 2. The three muscular vasodilators (PAP, BUF, NAF) had an immediate, powerful, dose-dependent but short lasting effect since only after 1600 microgram . kg-1 of PAP, there was still a significant vasodilator effect after the tenth minute. Little or no effect was observed on systemic blood pressure except for the higher doses of these compounds which produced a slight decrease accompanied by a simultaneous tachycardia. 3. The two ergot derivatives NIC and DHT caused a moderate but much longer acting decrease of femoral resistance although 100 micrograms . kg-1 DHT also caused an increase of the femoral resistance. This biphasic effect has been already described on other experimental models. The higher doses of these compounds decreased systemic blood pressure and produced a slight bradycardia as already reported (Boismare and Lefrancois, 1978; Huchet et al., 1981; Moore et al., 1981). The pressor effect of noradrenaline was reversed by NIC and DHT, confirming their alpha adrenoceptor blocking properties.