Changes induced by diazepam in the synaptic vesicle size of rat phrenic nerve terminals

The effect of diazepam (Valium), administered by i.p. injection on the cross-sectional area of synaptic vesicle profiles of the endplate-rich area of the rate diaphragm was studied by electron microscopy at 15–180 min after treatment. In the dose range of 0.25–10 mg/kg, diazepam induced a significant increase of the size of the synaptic vesicles. This increase was dose-related within a certain margin, dependent on the treatment time, while the effect of each dose increased significantly with the period after treatment. At 2.5–10 mg/kg a maximum seemed to be reached at 90 min.