Final answer:
Preganglionic neurons release acetylcholine (ACh) in both sympathetic and parasympathetic divisions. Postganglionic sympathetic neurons release norepinephrine, while postganglionic parasympathetic neurons release ACh.
Step-by-step explanation:
All preganglionic neurons, both in the sympathetic and parasympathetic divisions of the autonomic nervous system, release acetylcholine (ACh). These neurons have nicotinic receptors on their targets, which are ganglionic neurons. Nicotinic receptors are ligand-gated cation channels that depolarize the postsynaptic membrane. Postganglionic parasympathetic neurons also release ACh, which binds to muscarinic receptors on their target cells. On the other hand, postganglionic sympathetic neurons release norepinephrine, except for those that project to sweat glands and blood vessels associated with skeletal muscles, which release ACh.