Continuous infusion of somatostatin evokes escape of gastric acid inhibition in the rat.

In rats with chronic gastric fistula, constant infusion of somatostatin failed to maintain a sustained inhibition of basal and pentagastrin-stimulated gastric acid secretion for greater than 4-6 h. After 8-12 h, the secretion was back to the level observed before infusion of somatostatin. The desensitization seemed specific in that infusion of secretin at this stage inhibited the secretion. After interruption of an 18-h-infusion, the responsiveness to somatostatin returned gradually; it was completely restored at 2 h. In marked contrast, intermittent administration of somatostatin produced a sustained pulsatile response pattern of the pentagastrin-stimulated acid secretion over a period of 18 h, the rhythm selected being 20 min of somatostatin + pentagastrin infusion followed by 40 min of pentagastrin alone. The desensitization to somatostatin is of particular interest in view of the postulated paracrine nature of the somatostatin cells in the stomach.