The main reason for giving levodopa the precursor of dopamine instead of dopamine is:

Correct Answer: A

Rationale: The correct answer is A because levodopa, as a precursor of dopamine, can cross the blood-brain barrier and be converted to dopamine in the brain, while dopamine itself cannot cross the blood-brain barrier when administered peripherally. Choice B is incorrect because dopamine-induced psychotic reactions are not the main reason for choosing levodopa. Choice C is also incorrect as levodopa is metabolized in the periphery before reaching the brain. Therefore, the correct choice is A as it addresses the main reason for using levodopa over dopamine.

Correct Answer: B

Rationale: Neuroleptics are primarily used to treat psychosis, which includes symptoms like hallucinations and delusions. These medications work by blocking dopamine receptors in the brain to reduce these symptoms. Neurosis (choice A) is a milder condition characterized by anxiety and distress, typically treated with psychotherapy. Narcolepsy (choice C) is a sleep disorder treated with stimulants. Parkinsonian disorders (choice D) are movement disorders and are treated with medications that increase dopamine levels. Therefore, the correct answer is B as neuroleptics are specifically designed to address symptoms associated with psychosis.

Correct Answer: B

Rationale: The correct answer is B: Blocking a major degradative pathway for the amine neurotransmitters, which permits more amines to accumulate in presynaptic stores. MAO inhibitors work by blocking the enzyme monoamine oxidase, which is responsible for breaking down neurotransmitters like serotonin, dopamine, and norepinephrine. By inhibiting this enzyme, MAO inhibitors allow these neurotransmitters to accumulate in the synaptic cleft, leading to increased neurotransmission. A: Blocking the amine reuptake pumps is the mechanism of action for tricyclic antidepressants, not MAO inhibitors. C: Inhibiting the storage of amine neurotransmitters in vesicles is not a known mechanism of action for MAO inhibitors. D: Antagonism of alpha2-norepinephrine receptors is the mechanism of action for alpha2-adrenergic receptor antagonists, not MAO inhibitors.

Correct Answer: C

Rationale: The correct answer is C because Bemegride has both central and reflector effects. It acts centrally by stimulating the medullar respiratory center (not inhibiting it as in choice A), and peripherally by stimulating chemoreceptors in the carotid sinus zone (not acting as a spinal analeptic as in choice D). Therefore, choice C accurately describes the dual mechanism of action of Bemegride, making it the correct choice.

Correct Answer: A

Rationale: The correct answer is A because tranquilizers typically produce euphoria, burst of energy, increase in motor activity, and a warm sensation throughout the body. This is due to the sedative effects of tranquilizers, which can initially induce feelings of relaxation and well-being. Choice B is incorrect because visual hallucinations and distorted perception of time and space are more commonly associated with hallucinogens rather than tranquilizers. Choice C is incorrect because physical bliss, body lightness, a wish to fly, and motionlessness are not typical effects of tranquilizer intoxication. Choice D is incorrect because synaesthesia, where senses mix and one sensory experience triggers another, is not a common effect of tranquilizers intoxication. In summary, choice A is the correct answer as it aligns with the typical features of tranquilizers intoxication, while the other choices do not accurately describe the effects of tranquilizers.