A ganglionic blocker (or ganglioplegic) is a type of medication that inhibits transmission between preganglionic and postganglionic neurons in the autonomic nervous system, often by acting as a nicotinic receptor antagonist.
[1] Nicotinic acetylcholine receptors are found on skeletal muscle, but also within the route of transmission for the parasympathetic and sympathetic nervous system (which together comprise the autonomic nervous system).
More specifically, nicotinic receptors are found within the ganglia of the autonomic nervous system, allowing outgoing signals to be transmitted from the presynaptic to the postsynaptic cells.
Some substances can exhibit both stimulating and blocking effects on autonomic ganglia, depending on dosage and/or duration of action.
[3] Nicotinic receptor antagonists: Nicotinic receptor agonists (acting through depolarization block): Blocking ACh release in autonomic ganglia (although these have many other actions elsewhere): Ganglionic blockers are used less frequently now than they were in the past, because antihypertensives with fewer side effects are now available.