The mechanisms involved in the rapid glucagon-like peptide-1 (GLP-1) release following glucose ingestion are poorly defined. Be- sides a direct intestinal stimulation of L cells, humoral and neuronal mechanisms have been discussed. We investigated the temporal pat- tern of GLP-1 release in five healthy men (aged 27.8 6 3.6 yr; body mass index, 23.4 61.2 kg/m2) after an overnight fast for 60 min under basal conditions and for 60 min after an oral glucose load (OGL; 100 g) in both the presence and absence of atropine (80 ng/kgzmin, iv). Blood was sampled every 2 min, and data were evaluated for the temporal pattern of GLP-1 secretion by several computer-assisted programs (deconvolution, Pulsar analysis, and Fourier transformation). With all methods a pulsatile pattern of plasma GLP-1 levels with a fre- quency of five to seven per h was detected; this remained unchanged in the different metabolic states and during atropine treatment. Glu- cose and GLP-1 plasma levels showed a parallel increase after OGL (OGL without atropine 5 control: 8.4 6 2.9 and 7.9 6 3.0 min, re- spectively). Atropine infusion delayed this increase significantly (16.8 6 8.07 and 17.4 6 6.61 min, respectively; P , 0.02). In contrast to plasma glucose concentrations (82.7 6 0.3% of control; P , 0.05), atropine infusion reduced the integrated GLP-1 pulse amplitude to 56.0 6 11.3% of the control levels (P , 0.05). In conclusion, GLP-1 is secreted in a pulsatile manner with a frequency comparable to that of pancreatic hormones. Mean GLP-1 plasma concentrations increase after OGL due to augmented GLP-1 pulse amplitudes but not frequency. The differential effect of atropine on glucose and GLP-1 plasma levels suggest a direct cholinergic mus- carinic control of L cells. (J Clin Endocrinol Metab82:786-790, 1997)