The release of endogenous acetylcholine from the medial septum/diagonal band of rat brain

This study sought to establish whether cholinergic neurons in the medial septum/vertical limb of the diagonal band (ms/vdB) release endogenous acetylcholine (ACh) locally, and whether the release was modulated by presynaptic feedback mechanisms. Release of ACh from slices of the ms/vdB was assessed by gas chromatography-mass spectrometry (GC-MS). Potassium depolarization resulted in a 20- to 25-fold increase in ACh release above spontaneous levels. Omission of Ca2+ from the incubation medium decreased this release by 91%. In the presence of 4 microM atropine, potassium-induced ACh release was enhanced by 48%. These results indicate that ACh is released in the ms/vdB by a Ca2+-dependent and atropine-sensitive process.