Cholinesterase activity of the motor endplate in rat intercostal muscle

Cholinesterase activity was localized solely in the motor endplate of the membrane in rate intercostal muscle. The diameter of rat motor endplates in the gradient dimension was 31.9 micrometers. The cholinesterase activity per unit protein of the soluble fraction of rat muscle membrane was 35.6% higher than the original membrane. From studies with specific substrates and cholinesterase inhibitors, the cholinesterase activity of rat muscle membrane and its soluble fraction consists of more than 90% acetylcholinesterase and less than 10% pseudocholinesterase.