Final answer:
Drugs affecting both divisions of the autonomic nervous system likely target nicotinic receptors, which bind acetylcholine from preganglionic neurons. The postsynaptic receptors in the parasympathetic system are predominantly muscarinic, whereas the sympathetic system primarily uses adrenergic receptors for signaling.
Step-by-step explanation:
The autonomic nervous system includes adrenergic response receptors, which are alpha (α)-adrenergic and beta (β)-adrenergic receptors, and cholinergic response receptors, which are nicotinic and muscarinic receptors. Both α and β-adrenergic receptors are G protein-coupled receptors. Alpha receptors have three types (α₁, α₂, and α₃), while beta receptors have two (β₁ and β₂). A drug that affects both the sympathetic and parasympathetic branches of the autonomic nervous system would likely interact with nicotinic receptors, as both preganglionic sympathetic and parasympathetic neurons release acetylcholine (ACh) which binds to nicotinic receptors on ganglionic neurons.
All postganglionic parasympathetic fibers and select postganglionic sympathetic fibers (to sweat glands and blood vessels associated with skeletal muscle) release ACh that binds to muscarinic receptors. On the other hand, most postganglionic sympathetic fibers release norepinephrine that binds to α-adrenergic or β-adrenergic receptors. Notably, epinephrine can also bind to these adrenergic receptors, with the primary difference between epinephrine and norepinephrine being the presence of an additional methyl group (CH₃) in epinephrine.