Final answer:
The neurotransmitter in the synapse between pre- and postganglionic autonomic neurons is acetylcholine (ACh).
Step-by-step explanation:
The neurotransmitter in the synapse between pre- and postganglionic autonomic neurons is acetylcholine (ACh).
All preganglionic fibers, both sympathetic and parasympathetic, release ACh.
All ganglionic neurons, the targets of these preganglionic fibers, have nicotinic receptors in their cell membranes.
The nicotinic receptor is a ligand-gated cation channel that results in depolarization of the postsynaptic membrane.