Deck 16: Extracellular Messengers

Question 1

g-Aminobutyric acid (GABA) is the most important inhibitory neurotransmitter in the brain, and reduced action of GABA can lead to epileptic seizures.Therefore, a good strategy for the treatment of epilepsy would be:

A)An inhibitor of GABA decarboxylase.
B)A drug that binds to the GABA-binding site of the GABA receptor without activating the receptor.
C)An inhibitor of glutamate decarboxylase.
D)An inhibitor of GABA transaminase.
E)An inhibitor of glutamate dehydrogenase.

Answer 1

An inhibitor of GABA transaminase.

Question 2

An 18-year-old girl is evaluated for primary amenorrhea.The external genitalia are unambiguously female, and secondary sexual characteristics appear normally developed.The karyotype is 46,XY.Estrogen and testosterone levels are in the normal male range.This condition is most likely caused by:

A)Deficiency of aromatase in all tissues.
B)Deficiency of 21-hydroxylase in the adrenal cortex.
C)Deficiency of desmolase.
D)A defective androgen receptor.
E)A defect of adrenocorticotropic hormone secretion from the anterior pituitary gland.

Answer 2

A defective androgen receptor.

Question 3

Thromboxane is formed in platelets, where it promotes platelet activation.The formation of thromboxane can be suppressed by inhibitors of:

A)21-Hydroxylase.
B)5a-Reductase.
C)Lipoxygenase.
D)Desmolase.
E)Cyclooxygenase.

Answer 3

Cyclooxygenase.

Question 4

Increased activity of the neurotransmitter dopamine at synapses in the mesolimbic dopamine system is known to cause euphoria.Therefore, a good strategy for the development of new euphoriants is to develop drugs that:

A)Inhibit the sodium cotransporter for dopamine in the nerve terminal.
B)Inhibit the transporter that pumps dopamine into synaptic vesicles.
C)Inhibit tyrosine hydroxylase.
D)Induce enhanced expression of catechol-O-methyltransferase (COMT).
E)Block voltage-gated calcium channels in the nerve terminals.

Question 5

During the synthesis of steroid hormones, side chain cleavage reactions occur in two biotransformations.These are:

A)Glucocorticoids → mineralocorticoids and progestins →androgens.
B)Progestins → corticosteroids and androgens → estrogens.
C)Cholesterol → progestins and estrogens → androgens.
D)Cholesterol → progestins and progestins → androgens.
E)Androgens → corticosteroids and androgens → estrogens.

Question 6

The polyunsaturated fatty acid eicosapentaenoic acid, which is abundant in fish oils, is a precursor for the synthesis of:

A)Arachidonic acid.
B)Linoleic acid.
C)Thromboxane A3.
D)Platelet activating factor.
E)Prostaglandin E2.

Question 7

The release of neurotransmitters from the nerve terminal depends on an increase in the cytoplasmic level of:

A)Sodium.
B)Calcium.
C)Magnesium.
D)Cyclic adenosine monophosphate.
E)Inositol-1,4,5-trisphosphate.

Question 8

The polyunsaturated fatty acid that is most abundant in fish oils is known as eicosapentaenoic acid.It is a precursor for the synthesis of:

A)Arachidonic acid.
B)Linoleic acid.
C)Thromboxane A3.
D)Platelet-activating factor.
E)Prostaglandin E2.

Question 9

Aspirin inhibits the synthesis of:

A)Prostacyclin.
B)Leukotrienes.
C)Platelet-activating factor.
D)Bradykinin.
E)Free arachidonic acid from membrane lipids.

Question 10

Renin plays a role in blood pressure regulation.What exactly does it do?

A)Contracts blood vessels and thereby raises the blood pressure.
B)Degrades angiotensin.
C)Makes angiotensin.
D)Prevents the degradation of bradykinin.
E)Stimulates the bone marrow, thereby increasing the blood volume and raising the blood pressure.

Question 11

Catecholamine biosynthesis involves dopamine (DA), epinephrine (Epi), norepinephrine (Norepi), and L-dopa (DOPA).In what sequence are these products formed?

A)Epi → Norepi → DOPA → DA.
B)DOPA → Epi → Norepi → DA.
C)DOPA → DA → Norepi → Epi.
D)DA → DOPA → Epi → Norepi.
E)Epi → Norepi → DA → DOPA.