Drugs Acting on the Nervous System Questions and Answers

Answer: D

The herbal mild tranquilizer is valerian.

Valerian root has calming and mild sedative effects and is used in dogs for anxiety, nervousness and sleeplessness, for example during travel or fireworks.

Ginkgo is used for circulation and cognitive decline in older animals, ginseng as a tonic for energy, and cranberry for the health of the urinary tract. None is a tranquilizer.

Answer: B

The tricyclic antidepressant is amitriptyline.

Tricyclic antidepressants have a three-ring structure and block the reuptake of noradrenaline and serotonin. Amitriptyline is the classic example, together with imipramine and clomipramine, and they also cause anticholinergic side effects such as dry mouth and constipation.

Nefazodone is an atypical antidepressant that blocks serotonin receptors. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI). Isocarboxazid is a monoamine oxidase inhibitor. None of them is a tricyclic.

Answer: B

The benzodiazepine hypnotic is flurazepam.

Flurazepam is a long-acting benzodiazepine used for insomnia. Like other benzodiazepines it enhances GABA-A receptor activity, and its long-acting metabolite helps keep the patient asleep through the night but can cause hangover the next day.

Zolpidem (spelt 'Zolpiderm' in the paper) acts at the benzodiazepine site but is an imidazopyridine, a non-benzodiazepine 'Z-drug'. Secobarbital and phenobarbitone are barbiturates, an older class of hypnotics.

Answer: A

The competitive ganglion blocker in the amine group is mecamylamine.

Ganglion blockers that compete with acetylcholine at the nicotinic receptors of autonomic ganglia are classed as quaternary ammonium compounds (hexamethonium, pentolinium) and amines (mecamylamine, pempidine). Mecamylamine is a secondary amine, so it is well absorbed by mouth.

Hexamethonium is a competitive blocker, but a quaternary ammonium compound, not an amine. Nicotine in large doses blocks ganglia by persistent depolarisation, not by competition. Acetylcholine is the ganglionic transmitter itself, which stimulates rather than blocks.

Answer: A

The reversible carbamate anticholinesterase is physostigmine.

Physostigmine, an alkaloid from the Calabar bean, carbamylates acetylcholinesterase. The carbamylated enzyme recovers within hours, so its action is reversible. Neostigmine and pyridostigmine belong to the same carbamate group. Being a tertiary amine, physostigmine enters the brain and is used in atropine poisoning.

Echothiophate is an organophosphate, an irreversible anticholinesterase. Muscarine and carbachol are not enzyme inhibitors at all: they act directly on cholinergic receptors as agonists.