Ultrastructural identification of neurotransmitters.

It is apparent that the correlations made between intra-axonal vesicle types and the transmitters in cholinergic, adrenergic and non-adrenergic, non-cholinergic nerves in the early 1970's are too simplistic. The current proposals for 16 or more putative transmitters in the enteric nervous system and the additional possibility of co-existence of two or more transmitters within single nerve terminals, clearly complicate the issue. We must await preparative procedures that will lead to high quality electronmicrographs of nerve profiles following the application of specific cytochemical reactions for putative transmitters and associated enzymes before the problem will be resolved.