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Effect of mode of application of papaverine on the contractile response of the internal mammary artery

A study was performed to investigate the duration of action of papaverine applied either intraluminally or in a combined intraluminal and extraluminal fashion in vitro, and how the reactivity of the internal mammary artery (IMA) to a range of vasoconstrictors is affected. Segments of IMA exposed to only intraluminal papaverine (10−4 mol/1) for 15 min recovered their contractile response to 90 mmol/1 potassium chloride to pretreatment levels within 2h. In contrast, combined intraluminal and extraluminal administration of papaverine resulted in a significant depression of the contractile response to 90 mmol/1 potassium chloride (P<0–001), which persisted for at least 5 h. Responses to 5‐hydroxytryptamine, noradrenaline, the thromboxane mimetic U46619, histamine and dopamine were not significantly different between control tissues and those that had received intraluminal papaverine. The duration of action of papaverine is affected by its route of delivery and there are no significant short‐term effects on the contractile mechanisms in the arterial wall after intraluminal administration.