Action of neurotransmitters: acetylcholine, adrenaline and serotonin on arterial thrombosis induced by a laser beam.

The releasing of catecholamines is increased in stress situation which promotes the formation of circulating platelet aggregates, and could participate in the arterial thrombosis formation in coronary diseases. The purpose of this study is to evaluate the thrombogenic action of some neurotransmitters, and their participation through the vessel's vasomotoricity, in the growth of an arteriolar thrombosis. Endothelial cells destruction, induced by a laser beam in mesenteric arteriole of the rat were observed to determine changes in thrombus growth, through the embolization and variation of vessel diameter. It is desirable to get insight into the interrelation of thrombus formation and local vasomotoricity in the presence of acetylcholine, adrenaline and serotonin. The administration of acetylcholine (5mg/kg) increases the number of emboli which detached from thrombus, and decreases the thrombus area. Therefore, acetylcholine induces a variation of the vessel's diameter, a vasodilation in the intact vessel and a vasoconstriction when the endothelium is removed. Two vasoconstrictor agents are used: adrenaline and serotonin which increase the number of laser injuries required to induce thrombus formation, decrease the number of emboli and the duration of embolization (p < 0.05). They cause a potent vasoconstriction. These neurotransmitters seem to be involved in the arterial thrombosis induced by laser beam, promoting or not the platelet aggregation, and modulating the vascular tone by the endothelium.

Importance of photo activation of rose bengal for platelet activation in experimental models of photochemically induced thrombosis.

Generation of oxygen free radicals in the lumen of a vessel leads to NO inactivation, modification of lipid components of platelets and endothelial cell membranes, and platelet activation. On this basis, many experimental models of thrombosis have been developed, where the formation of a platelet rich thrombus follows the illumination of a vessel with an appropriately filtered light after intravenous administration of Rose Bengal or another sensitizing dye. However the detailed mechanism of thrombus formation remains poorly known. This work appreciates the contribution of platelet activation directly induced by oxygen free radicals in formation of the platelet rich thrombus, from a study of human platelet aggregation in presence of photo-activated Rose Bengal. The results demonstrate that direct activation of platelets by free radicals generated by Rose Bengal is of low or no importance in formation of the thrombus. Therefore, the main trigger of platelet aggregation and thrombosis in these models is primary endothelial cells injury.

Effect of monoclonal and polyclonal antibodies against conjugated neurotransmitter on experimental venous thrombosis.

Vasomotoricity in veins is largely controlled by the sympathetic nervous system. Norepinephrine and acetylcholine modulate the vasoconstrictor effect mediated by alpha-adrenergic receptors. Our objective was to study the role of local vasomotoricity in venous thrombosis, and particularly to determine some of the factors regulating it. Although no attempt has been described until now, polyclonal and monoclonal antibodies against L-dihydroxyphenylalanine, acetylcholine, and dopamine were administered in an experimental model of venous thrombosis. In view of the rather high specific antibody recognition for each compound, the presence of endogenous epitopes of L-dopa-like molecules and acetylcholine-like molecules in the circulation can be postulated. The results of this study may open an important new approach in the treatment of vascular diseases.