Final answer:
Direct acting cholinergic agents are divided into muscarinic agonists, with examples including pilocarpine and muscarine, and nicotinic agonists such as nicotine. These drugs stimulate their respective receptors to increase cholinergic activity, which is beneficial in various medical treatments.
Step-by-step explanation:
Direct acting cholinergic agents are classified into two groups based on their receptor targets: muscarinic agonists and nicotinic agonists. Muscarinic agonists such as pilocarpine and muscarine mimic the action of acetylcholine (ACh) on muscarinic receptors found throughout the body, including in the parasympathetic nervous system. Nicotinic agonists, like nicotine, specifically activate nicotinic receptors at the neuromuscular junction (NMJ) and other synapses.
Both types of agents increase cholinergic activity by directly stimulating the respective receptors. These drugs play key roles in treating a variety of conditions such as glaucoma or Myasthenia Gravis and for reversing the effects of neuromuscular blocking drugs used during anesthesia. Atropine is an example of a muscarinic antagonist, not an agonist, which is used to treat symptoms of nerve agent poisoning by blocking excess acetylcholine at muscarinic receptors.