A Possible Role for λ-Aminobutyric Acid in the Control of the Endocrine Pancreas

This study examines the effect of baclofen, a specific y-aminobutyric acid analog which crosses the blood-brain barrier freely, upon insulin, glucagon, and GH responses to i v glucose in normal man. Normal subjects received two consecutive iv glucose tolerance tests (0.33 g⁄kg) before and after the acute oral administration of 5, or 10 or 20 mg baclofen, respectively, (10 subjects for each group). The dose of baclofen was divided and given 8 and 1 h before the performance of the posttreatment test. A fourth group of normal subjects served as placebo group (8 subjects). The highest dose of baclofen signif-icantly increased insulin responses to glucose and raised basal glucagon levels (P < 0.01). No significant change occurred with the other doses. Baclofen produced a dose-related increase in basal GH levels; a 10-fold increase was observed with the 20-mg dose. However, glucose-induced glucagon and GH suppression were not affected by baclofen. Despite the increased hormonal secretions, glucose tolerance did...