Effect of L-arginine on lower oesophageal sphincter motility in man.

OBJECTIVE: Inhibitory responses of the lower oesophageal sphincter (LOS) are mediated via an L-arginine/nitric oxide (NO) pathway. L-arginine is known as the precursor of NO. We have studied the effect of intravenous L-arginine on LOS motility in man. DESIGN: Twelve healthy subjects participated in a double-blind, placebo-controlled randomized study. METHODS: We investigated the effect of continuous infusion of L-arginine (500 mg/kg body weight/120 min) in six subjects under fasting conditions. Six other subjects were studied under postprandial conditions. LOS pressure (LOSP), swallow-induced LOS relaxations and transient lower oesophageal sphincter relaxations (TLOSR) were measured with sleeve manometry combined with pH metry. The meal consisted of a carbohydrate-high fat meal. Blood samples were taken before and after administration of L-arginine or saline to determine plasma levels of amino acids, cholecystokinin and gastrin. RESULTS: Plasma levels of arginine and citrulline significantly (P < 0.05) increased during L-arginine infusion. L-arginine did not affect plasma hormone levels. Under fasting conditions, LOSP and TLOSR were not influenced by L-arginine. Ingestion of the carbohydrate-high fat meal significantly decreased LOSP. L-arginine did not significantly influence TLOSR frequency, either under fasting conditions or postprandially. CONCLUSIONS: These results suggest that in humans under fasting or postprandial conditions intravenous infusion of L-arginine does not influence LOS motility.

Neuropsychological impairment in chronic cocaine abusers.

Twenty chronic cocaine abusers were compared with age and education matched controls using standardized neuropsychological assessment procedures to determine whether the cocaine abusers were impaired. Fifty percent of the cocaine abusers in contrast to 15% of the controls scored in the impaired range on the summary index of the Neuropsychological Screening Exam. The cocaine abusers also performed more poorly on the Halstead Category Test, the Symbol Digit Modalities Test, the WAIS-R Arithmetic Test, and a test of verbal memory (forgetting). In the cocaine abuser sample, neuropsychological performance was related to the amount and recency of cocaine use, suggesting a direct role of cocaine on cognitive functioning.