Purity >95%. [Leu13]-Motilin (Human; Porcine) has been shown to produce an excitory response in the chicken gastrointestinal tract with a different sensitivity from region to region. The mechanisms of action were different between the proventriculus and the intestinal segments. The motilin analog contracted the intestinal segments by direct action on the smooth muscle cells whereas in the proventriculus it caused contraction and enhancement of electrical field stimulation-induced response through an action on the intramural cholinergic neurons.