Final answer:
Ganglionic blockers are medications that inhibit neurotransmission in autonomic ganglia by blocking nicotinic ACh receptors. They lack specificity, affecting both sympathetic and parasympathetic systems, leading to broad and unpredictable effects. While they have been used to treat hypertension, they have largely been replaced by more selective medications like ß-blockers.
Step-by-step explanation:
Ganglionic blockers are a group of medications that inhibit the transmission of nerve impulses in autonomic ganglia. These ganglia are collections of nerve cell bodies that relay signals from the central nervous system to the peripheral target organs in both the sympathetic and parasympathetic branches of the autonomic nervous system. Ganglionic blockers work by antagonizing the nicotinic acetylcholine (ACh) receptors, thereby preventing the action of ACh released from the preganglionic fibers.
Their selectivity is generally non-specific because these blockers affect both the sympathetic and parasympathetic ganglia. However, some degree of selectivity can be seen depending on the extent to which either system predominates in the control of certain organs.
Therapeutically, ganglionic blockers are not commonly used today due to their significant side effects and the development of more selective drugs. When used, they can treat conditions such as hypertension, particularly in emergency settings. However, their effects on both branches of the autonomic nervous system can lead to wide-ranging and often unpredictable outcomes.
An example of a ganglionic blocker is mecamylamine, which was used in the past to treat conditions like high blood pressure. Currently, more selective drugs like ß-blockers, such as metoprolol and propanolol, are preferred for treating cardiovascular conditions given their ability to specifically target ß-receptors associated with vasoconstriction and cardioacceleration.