The effect of a developing neo-intima on serotonergic and adrenergic contractions.

In the present study we used a new model, in which the positioning of a non-occlusive collar around the rabbit carotid artery results, within 7 days, in the generation of a neo-intima, a precursor lesion of atherosclerosis. We investigated the effects of this intimal proliferation on the responsiveness to serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline (NOR) after 1, 2 and 7 days. Already after 1 day the collar-treated arteries were more sensitive to 5-HT, but not to NOR. This sensitivity persisted over a period of 7 days. However, the development of a neo-intima diminished the maximum contractile force to NOR after 2 and 7 days, but not to 5-HT. These results demonstrate that there is a relatively selective increase in sensitivity to 5-HT during neo-intima formation, even without hyper-cholesterolaemia.