Involvement of the vagus nerve, substance P and cholecystokinin in the regulation of intestinal blood flow.

Intestinal blood flow was recorded in anesthetized rats and cats using laser-Doppler flowmetry (LDF). This new technique provides continuous and accurate measurements of the intestinal blood flow, without affecting the blood circulation. Electrical stimulation (1 ms, 5–30 V, 5–50 Hz) applied either afferent or efferent vagal fibres elicited changes in the intestinal blood flow consisting mainly of increases. Similar results were obtained upon applying chemical stimulation to intestinal sensory endings using cholecystokinin (CCK) or substance P (SP; 10–20 μg/kg intravenously given). Bilateral vagotomy and atropine treatment markedly reduced or suppressed these vascular effects. In addition, experiments in which the activation of gastrointestinal afferents were activated by applying electrical stimulation to the abdominal vagal nerves yielded similar results. Finally, these effects were reduced after selectively severing vagal afferents. It is concluded that intestinal blood changes may be triggered by activation of the sensory endings from the digestive organs through the vagal nerves.