Autonomic neurotransmitters and trophic factors.

Substantial changes to the classical view of two transmitters in the autonomic nervous system are discussed: there is now evidence that about 16 putative neurotransmitter substances exist; some transmitter substances coexist within single nerve terminals, and upon release may act as co-transmitters or as pre- or post-junctional neuromodulators, and autonomic nerves release 'trophic factors' which have long-term influences on development and regeneration. Thus these findings influence interpretation of the autonomic nervous system's function and pathophysiology.