But nerves in the intestine, lung and penis have long presented a mystery. Researchers have not been able to nail down the neurotransmitter being used. In fact these nerves have been named for what they are not, NANC nerves which stands for not adrenergic , not cholinergic. Well you guessed it, recent findings show that NANC nerves use nitric oxide as their neurotransmitter. That discovery has put a whole new category of nerve transmission into the textbooks.
Researchers now speak of nitrergic nerves alongside the other categories.
Some researchers are puzzled as to how a gas could possibly act as a neurotransmitter. Neurons generally go to a great deal of trouble to release their neurotransmitters with precision and speed. They package precise quantities of neurotransmitter into little torpedoes that lie ready and waiting at the nerve terminal. When detonated by a nerve signal, the torpedoes spew their contents precisely at targets on the receiving neuron. But nitric oxide as a neurotransmitter breaks all the rules.