The Uptake, Metabolism and Release of Homocholine: Studies With Rat Brain Synaptosomes and Cat Superior Cervical Ganglion

The accumulation of [3H]homocholine (3‐trimethylamino‐propan‐1‐01) by isolated synaptosomes prepared from rat brain was resolved kinetically into a high (KT= 3.0 μM) and a low (KT= 14.5 μM) affinity system. Although homocholine was not acetylated by solubilized choline acetyltransferase, 64% of the homocholine accumulated by intact synaptosomes via the high affinity uptake process was acetylated. Homocholine was also acetylated in the superior cervical ganglion of the cat, and the amount of acetylhomocholine formed was increased (12‐fold) by preganglionic nerve stimulation. In ganglia, acetylhomocholine was available for release by preganglionic nerve impulses, and its release was Ca2+‐dependent, It is concluded that homocholine can form a cholinergic false transmitter, and that the substrate specificity of choline acetyltransferase in vitro might be different from that in situ.