Characterization of α2-Adrenergic Receptors Mediated Vasoconstriction in ex vivo model

Introductionrat tail serves as a thermoregulatory organ by dilating or constricting tail blood vessels and rat tail lateral veins play a role in cutaneous circulation. However, this cutaneous vessel has never been examined and evaluated as a potential candidate ex vivo model to study peripheral vascular diseases. This study aims to investigate vascular tone mediated through α2-adenergic receptor on rat tail vein under different temperatures.MethodsVasoconstriction stimulated by α2-adrenergic receptor selective agonists UK14304, guanabenz was thoroughly examined in isolated rat tail lateral vein. Susceptibility of cutaneous vessel to temperature changes was investigated under 37 °C and 28 °C. Differentiated vascular reactivity exhibited at different temperature was further explored with different α2-adrenergic receptor selective agonists and validated with antagonism by α1-adrenergic receptor and α2-adrenergic receptor selective antagonist prazosin and RX821002, respectively.ResultsVascular tone of freshly isolated vein remained same compared with that of stored in pre-gassed physiologic buffer at 4 °C overnight. Presence of endothelium and repeated administration of UK14304 did not alter contractile property. Vessels away from torso (distal) showed significantly different contractile character compared with portion close to torso (proximal) at 28 °C but kept uniform at 37 °C. Enhanced vasoconstriction along with increased potency of α2-adrenergic receptor agonists UK14304 and guanabenz was consistently present at 28 °C, independent of temperature change orders. Potentiated vasoconstriction present at 28 °C was later proved via α2-adrenergic receptor alone.DiscussionHarvest and preparation of rat tail lateral vein was described in details. Contractile property of venous preparations stimulated by α2-adrenergic receptor selective agonists was first time examined. Differentiated vasoconstriction at moderate cooling temperature was described and confirmed to through α2-adrenergic receptor activation. Rat tail lateral vein is found valuable for studies of cutaneous circulation altered by temperature changes.