The effect of a neurotoxin (benzalkonium chloride) on the lower esophagus

Achalasia of the esophagus may be associated with abnormalities of the myenteric plexus (hypo- and anganglionosis). This report evaluates this relationship by studying the effect of benzalkonium chloride (BK, a topical neurotoxin) on the lower esophagus. Following midline laparotomy, topical BK (0.5%) was applied to the muscularis of the lower 1.0 cm of the esophagus for 30 min in 38 Sprague-Dawley rats (200 g). Thirty-eight additional rats acted as controls (unoperated, n = 19; sham laparotomy, n = 19). At 1 and 3 months animals were evaluated for weight gain, daily food intake (g/100 gm body wt), lower esophageal sphincter (LES) manometry, and contrast esophagram. At 3 months, the esophagus was evaluated for histologic study and acetylcholinesterase staining. Esophagram showed distal narrowing with proximal dilatation in BK rats (inner diameter 4.71 +/- 0.61 vs 6.17 +/- 0.58 in controls, P less than 0.001). Daily food intake was significantly less in BK rats (5.57 +/- 0.41 g vs controls 7.69 +/- 0.33 g P less than 0.001). Daily weight gain was also less in BK rats (1.13 +/- 0.34 vs controls 1.83 +/- 0.25, P less than 0.001). An increased LES pressure was noted in BK rats (5.45 +/- 0.89 mmHg vs controls 4.04 +/- 1.04 mmHg; P less than 0.1). A histologic study showed aganglionosis in BK rats with positive cholinesterase staining fibers compared to controls. Topical BK results in distal esophageal aganglionosis characterized by distal narrowing, proximal dilatation, decreased food intake, and limited weight gain when compared to controls. These findings are similar to those observed in achalasia and support a primary neurogenic cause for its etiology.