“…For instance, in the fetus, the acid response to gastrin appears to precede that of histamine, 5 unlike in the adult where histamine seems to be the final common mediator 1 . Pentagastrin has been shown to stimulate acid and somatostatin secretion in the stomach directly 26 and also indirectly via histamine 27–28 . The effect of pentagastrin, however, decreases with extended treatment, suggesting that either the receptors become saturated or desensitized or, alternatively, receptor expression may change to accommodate the prolonged stimulation 26 …”