| Popis: |
The presence of a network of perivascular nerve fibres has been demonstrated in the adventitia and at the adventitial-medial border of human coronary arteries and veins, and immunocytochemical studies have provided evidence of the co-existence of several neuropeptides in subpopulations of afferent and efferent nerve fibres, supplying the coronary vasculature. The vasoconstrictors neuropeptide Y and noradrenaline see to co-exist in adrenergic perivascular nerve fibres, as distinct from parasympathetic perivascular nerve fibres, and also as distinct from sensory nerves containing immunoreactivity to the vasodilators substance P and calcitonin gene-related peptide. On the other hand, immunoreactivity to the vasoconstrictor, endothelin, has been demonstrated throughout the endothelial cell layer of human coronary arteries and veins. Although the physiological function of these substances is still uncertain, both their rich supply in and around coronary arteries and veins and their capacity to induce significant changes in vascular tone suggest them to be involved in the regulation of coronary blood flow. |
