Blocking of the transmission of stimuli in autonomic ganglia. Pharmacologically, this is done by using drugs that occupy receptor sites for acetylcholine and by stabilizing the postsynaptic membranes against the actions of acetylcholine liberated from presynaptic nerve endings. The usual effects of drugs that cause ganglionic blockade are vasodilatation of arterioles with increased peripheral blood flow; hypotension; dilation of veins with pooling of blood in tissues, decreased venous return, and decreased cardiac output; tachycardia; mydriasis; cycloplegia; reduced tone and motility of the gastrointestinal tract with consequent constipation; urinary retention; dry mouth; and decreased sweating. Ganglionic blocking drugs are not often used to treat hypertension but are used to treat autonomic hyperreflexia and to produce controlled hypotension during certain types of surgery. Several drugs are available for ganglionic blocking.