The effects of stimulating vasoconstrictor fibres and infusing noradrenaline and vasopressin on intestinal vascular resistance were studied in cats, using either constant flow or constant pressure. The responses to stimulating constrictor fibres and to infusing noradrenaline were essentially the same whether pressure or blood flow was kept constant, and the earlier described autoregulatory escape was of about the same magnitude during both these conditions. The results further support the hypothesis that a redistribution of blood flow takes place within the intestinal wall, and the combined evidence suggests an increased submucosal flow at the expense of the mucosa. The similarities between infusing noradrenaline and stimulating constrictor fibres suggest that the vasoconstrictor fibre endings and the α‐receptors may have a differentiated distribution in the intestinal bed. This view is supported by the fact that another vasoconstrictor agent, vasopressin, produces a well sustained vasoconstrictor response without secondary adjustments. Some similarities between ‘autoregulatory escape’ during nerve stimulation and autoregulation of blood flow at different pressures are pointed out. It is further emphasized that both these phenomena are very often diminished, distorted or even totally suppressed by the introduction of an artificial pump system.
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Dresel et al. (1966) studied this question.