1. Intracellular recordings of membrane potentials have been made in vitro from the exocrine acinar cells of the mouse pancreas using glass micro-electrodes.2. The mean membrane potential of the acinar cells was -41·2 mV. Spontaneous miniature depolarization potentials of 0·5-5·0 mV amplitude and occurring at random intervals were often observed superimposed upon the resting membrane potential. Atropine 2·8 × 10-6 M decreased, and physostigmine 1·23 × 10-5 M increased, the frequency and amplitude of the miniature potentials.3. Electrical stimulation of the pancreatic nerves depolarized the acinar cells. Acetyl β-methylcholine 10-6 M produced a sustained depolarization. Atropine 1·4 × 10-6 M blocked the depolarization to both electrical stimulation and acetyl β-methylcholine.4. Pancreozymin depolarized the exocrine acinar cells but secretin did not.5. These results suggest that the miniature depolarization potentials are of cholinergic origin and that depolarization of the pancreatic exocrine cells by nerve stimulation or pancreozymin may trigger secretion.
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