The defect in achalasia cardia is present in

Achalasia is characterized by impaired esophageal body peristalsis and incomplete lower esophageal sphincter relaxation. It is a rare disease caused by loss of ganglion cells within the esophageal myenteric plexus usually presenting between age 25 and 60. With longstanding disease, aganglionosis is noted. The disease involves both excitatory (cholinergic) and inhibitory (nitric oxide) ganglionic neurons. Functionally, inhibitory neurons mediate deglutitive lower esophageal sphincter (LES) relaxation and the sequential propagation of peristalsisRef: Harrison&;s Principles of Internal Medicine; 19th edition; Chapter 347 Diseases of the Esophagus; Page no: 1904