Quiz 8: Drugs Affecting the Autonomic Ganglia
The autonomic nervous system of human beings consists of sympathetic and parasympathetic nervous system. The fact is that autonomic ganglia present in both sympathetic as well as parasympathetic nerves are pharmacologically identical. The neurotransmitter present both these autonomic ganglia is acetylcholine (Ach). The nicotine was considered to stimulate the autonomic ganglia in the previous times when acetylcholine was not yet discovered. Due to this reason receptors were known by the name of nicotinic receptors. Nowadays these receptors present at the autonomic ganglia of both sympathetic and parasympathetic nervous systems have been more specifically classified and known as nicotinic-neural (Nn) receptors. Thus, it can be concluded that acetylcholine is the neurotransmitter present at the autonomic ganglia that functions to stimulate the Nn receptors.
According to the data given in the question the person is having dryness in mouth, and constipation. He complains that his feeling for sex has decreased due to gastro-intestinal disturbances since the administration of the drug. The patient is being treated for high blood pressure i.e. hypertension. From the data given it can be concluded that the patient is being given mecamylamine i.e. ganglionic blocker for the treatment of hypertension. The side effects of this drug are dryness of mouth, and decrease in gastro-intestinal activity. The other adverse effects include constipation, visual disturbances like the condition of mydriasis and cycloplegia and hypotension due to decrease in cardiac output. The use of these drugs in males is known to cause the condition of impotence.
Autonomic Nervous System maintains the visceral processes and bodily functions. It is mainly divided into the Sympathetic Nervous System and the Parasympathetic Nervous System. The motor outflow of them is connected by sets of preganglionic and postganglionic neurons. The energy from environments both external and internal are connected by receptors. In presynaptic sites, specific receptors are present for various neurotransmitters. If a cell is activated, multiple cells activate and work in this way. Receptors that get activated by binding to acetylcholine, a neurotransmitter are called cholinergic receptors. These are of 2 types based on the drug that is used that is nicotine and muscarinic drugs. Nicotinic-muscle(Nm) receptors or muscle-type nicotinic receptors are nicotinic acetylcholine receptors. They are present at neuromuscular junctions, where the action potential is transmitted from nerve to muscle. Hence option (B) is wrong. Muscarinic is one of the types of cholinergic receptors. These receptors get activated by binding to acetylcholine. They are associated with the parasympathetic nervous system. Located in glands, smooth muscle. Hence option (C) is wrong. Anticholinergic inhibits the action of the neurotransmitter acetylcholine. They inhibit parasympathetic nerve impulses. They inhibit the binding of acetylcholine to muscarinic acetylcholine receptors than nicotinic acetylcholine receptors as anticholinergic agents comprise mainly of antimuscarinic drugs. Hence option (D) is wrong. Receptors binding epinephrine and norepinephrine are adrenergic receptors. These are of 5 types in the sympathetic nervous system. They are alpha-1, alpha-2, beta-1, beta-2, beta-3. Hence option (E) is wrong. Nicotinic-neural (Nn) is one of the types of cholinergic receptors. These receptors get activated by binding to acetylcholine. The sympathetic postganglionic neurons and parasympathetic postganglionic neurons are stimulated by these receptors to release chemicals. They are present in the Central Nervous System and Peripheral Nervous System. So, these receptors are located on the ganglia of both autonomic nerve divisions. Hence option is correct.