Regarding the ENS, The descending interneurons release (1) to initiate relaxation of the circular muscle so that the bolus of food can move down the duodenum towards the anus. The descending interneurons release (2) to initiate contraction of the longitudinal muscle so that the bolus of food can move down the duodenum towards the anus. 1) NO and VIP 2) NO 1) NO and ACh 2) ACh and VIP 1) VIP 2) NO 1) NO and VIP 2) ACh and SP.