Investigations of the Relationship Between Acetylcholine Synthesis and the Recycling of Synaptic Vesicles

It is well established that synaptic vesicles fuse with the pre-synaptic membrane during stimulation, and are reformed during a period of rest. These events have been correlated with the depletion and resynthesis of stores of acetylcholine (Ach) in the frog neuromuscular junction. Thus, choline acetylase (ChAc) activity appears to be a key factor in the metabolism of the transmitter Ach pool. The present work inquires into the possible interrelationship of the above events; that is, whether the reformation of vesicles after depletion by stimulation is associated with the activity of ChAc. Therefore, a series of experiments on frog neuromuscular junctions were performed in which the data from biochemical analyses of acetylcholine synthesis and from the morphometric determination of vesicle numbers were compared.

Fine Structural Localization of Choline Acetylase at the Neuromuscular Junction

During the past several years we have investigated a variety of acyI transferases by combining biochemical, cytochemical and electron microscopic techniques. In each case biochemical justification of each of the cytochemical steps was established prior to the application of cytochemistry to electron microscopy to indicate fine structural localization of the enzymatic activity. Among the enzymes studied have been carnitine acetyl transferase, the mono glyceride pathway of synthesis of triglycerides and the alpha-glycerophosphate pathway of phospholipid synthesis in the absorptive cells of the small intestine as well as the alpha-glycerophosphate pathway of synthesis of phospholipid in hepatic cells. Pathways for the synthesis of phospholipids were also used to study several examples of membrane biogenesis.