Much of the research on hallucinogenic drugs such as LSD has focused

1. According to the passage, which of the following is one of the primary factors that led researchers studying hallucinogenic drugs to focus on serotonin?

Refer: Para1-
“ There are two major reasons for this emphasis. First, it was discovered early on that many of the major hallucinogens have a molecular structure similar to that of serotonin”

(A) The suppression of the activity of serotonin-secreting neurons by the administration of hallucinogens
(B) The observed similarities in the chemical structures of serotonin and hallucinogens
(C) The effects the administration of hallucinogens has on serotonin production in the human brain
(D) Serotonin-induced changes in the effects of hallucinogens on behavior
(E) Hallucinogen-induced changes in the effects of serotonin on behavior

B is the right answer

2. It can be inferred that researchers abandoned the presynaptic hypothesis because

Refer para 3- Hypothesis was tested and results opposed the assumption of presynaptic hypothesis

(A) a new and more attractive hypothesis was suggested
(B) no research was reported that supported the hypothesis
(C) research results provided evidence to counter the hypothesis
(D) the hypothesis was supported only by studies of animals and not by studies of human beings
(E) the level of technical expertise in the field of brain research did not permit adequate testing of the hypothesis

C is the right answer IMO

3. Which of the following best expresses the main idea of the passage?

(A) Research has suggested that the neurotransmitter serotonin is responsible for the effects of hallucinogenic drugs on the brain and on behavior.

It is opposite actually

(B) Researchers have spent an inadequate amount of time developing theories concerning the way in which the effects of hallucinogenic drugs occur.
Not main point ad also we do not know about research time

(C) Research results strongly suggest that hallucinogenic drugs create their effects by acting on the serotonin receptor sites located on target neurons in the brain.

This is an interesting fact presented in the passage and it is kind of result of the entire research and various hypothesizes

(D) Researchers have recently made valuable discoveries concerning the effects of depleting the amount of serotonin in the brain.
Not a main point

(E) Researchers have concluded that hallucinogenic drugs suppress the activity of serotonin-secreting neurons.
Not the main point; however entire research work is to test various possibilities

C is the best to be the main point

4. The research described in the passage is primarily concerned with answering which of the following questions?

Refer first Para

(A) How can researchers control the effects that LSD has on behavior?
(B) How are animals’ reactions to LSD different from those of human beings?
(C) What triggers the effects that LSD has on human behavior?
(D) What technical advances would permit researchers to predict more accurately the effects of LSD on behavior?
(E) What relationship does the suppression of neuron activity have to the occurrence of “serotonin syndrome”?

C is the answer

5. Which of the following best defines “serotonin syndrome” (Highlighted) as the term is used in the passage?

Refer last Para :
The fact that LSD elicits “serotonin syndrome”—that is, causes the same kinds of behaviors as does the administration of serotonin—in animals whose brains are depleted of serotonin indicates that LSD acts directly on serotonin receptors,

(A) The series of behaviors, usually associated with the administration of serotonin, that also occurs when LSD is administered to animals whose brains are depleted of serotonin
(B) The series of behaviors, usually associated with the administration of LSD, that also occurs when the amount of serotonin in the brain is reduced
(C) The maximal suppression of neuron activity that results from the destruction of serotonin-secreting neurons
(D) The release of stores of serotonin from serotonin-secreting neurons in the brain
(E) The proliferation of serotonin receptor sites that follows depletion of serotonin supplies in the brain

A is the answer

6. Which of the following best describes the organization of the argument that the author of the passage presents in the last two paragraphs?


In the 2nd lats para -Earlier hypothesis is described and rejected and in the next para a new hypothesis is presented

(A) Two approaches to testing a hypothesis are described, and the greater merits of one approach are indicated.
(B) The assumptions underlying two hypotheses are outlined, and evidence for and against each hypothesis is discussed.
(C) A phenomenon is described, and hypotheses concerning its occurrence are considered and rejected.
(D) The reasoning behind a hypothesis is summarized, evidence supporting the hypothesis is presented, and research that counters the supporting evidence is described.
(E) A hypothesis is discussed, evidence undermining the hypothesis is revealed, and a further hypothesis based on the undermining evidence is explained.

E is the answer IMO

7. The author’s attitude toward early researchers’ reasoning concerning the implications of similarities in the structures of serotonin and LSD molecules can best be described as one of


Refer Para 2:- Early investigators correctly reasoned that the structural similarity to the serotonin molecule might imply that LSD’s effects are brought about by an action on the neurotransmission of serotonin in the brain
The Author has shown agreement on the early researchers’ reasoning –

(A) complete agreement
(B) reluctant support
(C) subtle condescension
(D) irreverent dismissal
(E) strong opposition

A is the right answer IMO