Neurochemistry

Question 1

Which of the following neurotransmitters can be called catecholamines?

Select one:
1. Serotonin only
2. Dopamine only
3. Noradrenalin only
4. Dopamine and serotonin
5. Dopamine and noradrenalin

Answer 1

Dopamine and noradrenaline

All the three are monoamines, but dopamine and noradrenaline are catecholamines while serotonin is an indolamine.

Question 2

Which of the following type of glutamate receptors is crucial for the normal function of inhibitory interneurons?

Select one:
1. AMPA
2. GABA-B
3. NMDA
4. Sigma
5. Kainate

Answer 2

NMDA

Inhibitory interneurons comprise only about 20% of cortical neurons but have influential roles in cortical
maturation, function, and plasticity. NMDA receptors are predominantly located on these GABA interneurons.

Question 3

The neural mechanism of memory formation may include changes in physical properties of neurons and
synapses. One such change called LTP or Long Term Potentiation is mediated by

Select one:
1. Cannabinoid receptor CB1
2. NMDA receptor
3. GABA receptor
4. Adenosine A1
5. Serotonin 5HT2A

Answer 3

NMDA receptor

NMDA has a role in memory acquisition, developmental plasticity, epilepsy, and ischemic brain injury. NMDA receptor mediates long-term potentiation

Question 4

Which of the following best fits glucocorticoid receptor?

Select one:
1. Ionotropic
2. Ligand dependent regulators of nuclear transcription
3. Receptors with intrinsic enzyme activity
4. Metabotropic
5. G protein coupled

Answer 4

Ligand dependent regulators of nuclear transcription

Glucocorticoids act via their binding to the intracellular GR (Glucocorticoid Receptor) which translocates to
the nucleus to modulate gene expression. The GR belongs to a nuclear receptor superfamily of
transcription factors.

Question 5

Which of the following receptors increase adenylate cyclase to stimulate cell machinery?

Select one:
1. Dopamine D2
2. Dopamine D3
3. Alpha 1
4. Dopamine D4
5. Beta adrenergic

Answer 5

Beta adrenergic

Alpha1 receptors phospholipase C coupled; Alpha 2 are Gi-coupled(inhibitory). Beta receptors Gs coupled -
so they increase adenylate cyclase.

Question 6

D1 and D2 receptors are mainly located in which of the following structures?

Select one:
1. Nucleus accumbens
2. Amygdala
3. Caudate-putamen
4. Prefrontal cortex
5. Hippocampus

Answer 6

Caudate and putamen

There are two families of DA receptors. D1 and D5 receptors (D1-like), which are positively coupled to
Cyclic AMP, increase cyclic AMP. D2, D3, D4 (D2-like) that inhibit and decreases cyclic AMP. D1 and D2 are
predominant in the caudate and putamen, D3-nucleus accumbens, D4– the prefrontal cortex, D5-
Hippocampus. Both D1 and D 2 have wide distribution (striatal, mesolimbic and hypothalamic) while D3 and
D4 are more localised (mesolimbic, cortical and hippocampal).

Question 7

Which neurotransmitter plays an important role in the neurochemical changes seen in Huntington’s
disease?

Select one:
1. Dopamine
2. Endorphins
3. Serotonin
4. GABA
5. Noradrenaline

Answer 7

GABA

Reduced GABA, Reduced glutamic acid decarboxylase, reduced acetyl choline, reduced substance P,
Raised somatostatin and reduced corticotrophin releasing factor are seen in Huntington’s disease.

Question 8

Which of the following substances serve as a precursor for GABA?

Select one:
1. Adrenaline
2. Dopamine
3. Glucagon
4. Butyrylcholinesterase
5. Glutamate

Answer 8

Glutamate

GABA is one of the most ubiquitous inhibitory neurotransmitters in the CNS, and an estimated 40% of all brain synapses use it. Within the cerebellum, Purkinje cells produce GABA. GABA projections are found arising in the striatum, terminating in the substantia nigra and Globus pallidus. Loss of these GABA neurones in the caudate and putamen occurs in Huntington’s chorea. Underactivity of the GABAergic
system would theoretically result in epilepsy and reduction in GABA-BDZ receptors have been
demonstrated in seizure foci.

Question 9

The drug ‘khat’ (Catha edulis) has effects comparable to

Select one:
1. Cannabis
2. Benzodiazepines
3. Alcohol
4. Amphetamine
5. LSD

Answer 9

Amphetamine

Cathinone is an alkaloid present in the leaves of the khat bush that grows in East Africa and southern
Arabia and is often chewed because of its stimulating properties. Cathinone, which is S(-)-alphaaminopropiophenone, has a pharmacological profile closely resembling that of amphetamine; indeed, in a wide variety of in vitro and in vivo experiments it was demonstrated that cathinone shares the action of amphetamine on CNS as well as its sympathomimetic effects; thus, for example, drug-conditioned animals will not distinguish between cathinone and amphetamine. It operates through the same mechanism as amphetamine; i.e. it acts by releasing catecholamines from presynaptic storage sites. Thus, much experimental evidence indicates that cathinone is the main psychoactive constituent of the khat leaf and that, in fact, this alkaloid is a natural amphetamine (Excerpt from Cathinone, a natural amphetamine.

Question 10

Where do phospholipids get produced in a cell?
Select one:

1. Ribosomes
2. Lysosomes
3. Smooth endoplasmic reticulum
4. Nucleus
5. Rough Endoplasmic reticulum

Answer 10

Smooth endoplasmic reticulum

Throughout the human body, especially in those cells that produce hormones and other secretory products,
a vast network of membrane-bound vesicles and tubules called the endoplasmic reticulum, or ER is
present. Smooth ER plays different functions depending on the specific cell type including lipid
(incl.phospholipid) and steroid hormone synthesis, breakdown of lipid-soluble toxins in liver cells, and
control of calcium release in muscle cell contraction.

Question 11

Glycine and d-serine both act as co-agonists at

Select one:
1. Dopamine receptors
2. NMDA receptors
3, GABA receptors
4. Adrenaline receptors
5. Acetylcholine receptors

Answer 11

NMDA receptors

Glycine and D-serine both act as co-agonists at NMDA receptors. The excitatory glycine site on the NMDA
receptor is called non-strychnine-sensitive glycine receptor.

Question 12

Which of the following neurotransmitters are not correctly matched with their precursors?

Select one:
1. Adrenaline-Noradrenaline
2. Dopamine-Tyrosine
3. Serotonin-Histidine
4. Noradrenaline-Dopamine
5. The Noradrenaline neurones originate in the brain stem, from a series of nuclei including the locus cereleus

Answer 12

Serotonin-Histidine

The biosynthesis of catecholamines starts from the conversion of tyrosine into L-dihydroxyphenylalanine (LDOPA) by tyrosine hydroxylase. L-DOPA is then decarboxylated by DOPA decarboxylase to form
dopamine. The conversion of dopamine to norepinephrine comes about by the action of the enzyme dopamine ß-hydroxylase. The rate-limiting enzyme in the biosynthesis of serotonin is tryptophan
hydroxylase. Here, tryptophan is converted to 5-hydroxytryptophan by tryptophan hydroxylase and by 5- hydroxytryptophan decarboxylase into serotonin. Histidine is the precursor of histamine not serotonin.

Question 13

The neurochemical changes in the brain reported in Alzheimer’s disease include

Select one:
1. Increased DOPA decarboxylase
2. Increased levels of choline acetyl transferase
3. Increased levels of acetyl cholinesterase
4. Increased GABA levels
5. Decreased levels of acetyl cholinesterase

Answer 13

Decreased levels of acetyl cholinesterase

The neurochemical changes in the brain reported in Alzheimers disease would include decreased levels of
acetylcholinesterase (AChE), decreased levels of choline acetyltransferase, decreased GABA levels and
decreased levels of noradrenaline.

Acetylcholinesterase, the enzyme that inactivates acetylcholine and thus inhibits cholinergic neurotransmission, is consistently decreased in the brains of patients with Alzheimer’s dementia. Such a decrease is also seen in the CSF and plasma of these patients. But note that despite this overall decrease, levels of this enzyme appears to be high in the vicinity of β-amyloid plaques - thus contributes to amyloidogenesis. Thus AChE Inhibitors are useful to treat this illness.

Question 14

Which of the following enzymes mediate several catalytic reactions involving amino acids that synthesize neurotransmitters such as dopamine, serotonin and tryptamine?

Select one:
1. Hydrolase
2. Reductase
3. Oxidase
4. Decarboxylase
5. Hydroxylase

Answer 14

Oxidase

Monoamine Oxidases are a family of enzymes that catalyze the oxidation of monoamines. They are present on the outer membrane of mitochondria.

Question 15

Which of the following is an ionotropic receptor?

Select one:
1. 5HT2A receptor
2. Dopamine D2 receptor
3. GABA-B receptor
4. GABA-A receptor
5. Norepinephrine receptor

Answer 15

GABA-A receptor

GABA-A - opens chloride channel; inhibitory - leads to hyperpolarization; made of five subunits and at least
14 subunit subtypes

All others are G-coupled protein receptors

Question 16

Regarding excitatory amino acids which one of the following statements is incorrect?

Select one:
1. Excitatory amino acid neurotransmitters are essential in learning and memory
2. Calcium entry in neurons is influenced by glutamate
3. Glutamate can be a potent neurotoxin when excessive
4. Ketamine is a selective agonist at NMDA receptors
5. Glutamate is the most abundant excitatory neurotransmitter

Answer 16

Ketamine is a selective agonist at NMDA recpetors

There are four main types of excitatory amino acid receptors; N-methyl D-aspartate (NMDA), amino-3
hydroxy 5-methyl 4-isoxazole propionate (AMPA), kainate and Metabotropic (G-protein coupled receptors).

Ketamine is a non-competitive antagonist at NMDA receptors. Glutamate is the major excitatory
neurotransmitter with a wide distribution in the brain. There is a possible link between the glutamate
receptor activation and long-term potentiation in the hippocampus as the physiological substrate of memory.

Glutamate transmission has been postulated to have a link with psychosis. Excess glutamate via NMDA
mediated, calcium-dependent excitotoxicity can result in neuronal damage.

Question 17

Stimulation of nicotine receptors leads to the release of which of the following neurotransmitters?

Select one:
1. Serotonin
2. Dopamine
3. Melatonin
4. Adrenaline
5. Norepinephrine

Answer 17

Dopamine

Nicotine is highly lipid soluble and rapidly enters the brain after inhalation (smoking). Nicotine receptors are
found on dopaminergic cell bodies, and stimulation of nicotine receptors leads to release of dopamine

Question 18

Which of the following receptors is stimulated when tobacco is smoked?

Select one:
1. Adrenergic (alpha)
2. Nicotinic
3. Muscarinic
4. Adenosine
5. Endocannabinoid

Answer 18

Nicotinic

Nicotine acts on nicotinic cholinergic receptors, which then leads to an increase in dopamine activity.

Question 19

The predominant CNS metabolite of noradrenaline is

Select one:
1. 5HIAA (Hydroxy Indole Acetic Acid)
2. COMT (Catechol-O-methyl transferase)
3. Vanillyl mendalic acid (VMA)
4. Coenzyme A
5. MHPG (3-methoxy,4-hydroxy phenyl glycol)

Answer 19

MHPG (3-methoxy,4-hydroxy phenyl glycol)

The CNS metabolite of noradrenaline is MHPG (3-methoxy,4-hydroxy phenyl glycol). Outside the brain, the peripheral metabolite is principally VMA (vanillyl mendelic acid: this is why the levels of VMA increases in peripheral noradrenaline producing tumours such as phaeochromocytoma). Noradrenaline or its
metabolites usually do not cross the BBB with the exception of MHPG.

Question 20

A 44-year-old woman is on antipsychotic depot injections. She develops a white discharge from her
breasts. Hyperprolactinemia is noted. Which of the following dopamine pathways has a role in prolactin
regulation?

Select one:
1. Mesolimbic
2. Incertohypothalamic
3. Mesocortical
4. Nigrostriatal
5. Tuberoinfundibular

Answer 20

Tuberoinfundibular

Dopaminergic pathways can be classified as 1. Long: Nigrostriatal (movement), mesocortical and
mesolimbic. 2. Short: Tuberoinfundibular (prolactin inhibiting), incertohypothalamic 3. Ultrashort: amacrine cells in the retina, olfactory system.

Question 21

Which of the following is an amino acid neurotransmitter?

Select one:
1. Glycine
2. Acetylcholine
3. Neurotensin
4. Dopamine
5. Endorphins

Answer 21

Glycine

The important inhibitory amino acids are GABA and glycine. Excitatory amino acids are glutamic acid,
aspartate and homocysteine. Glycine is synthesized primarily from serine by serine trans-hydroxymethylase and glycerate dehydrogenase, both of which are rate limiting. Glycine acts as a mandatory adjunctive neurotransmitter for glutamate activity and an independent inhibitory neurotransmitter at its own receptors.

Question 22

Which of the following are carrot-shaped eosinophilic inclusions seen in hematoxylin and eosinophilic
stains?

Select one:
1. Rosenthal fibres
2. Pick cells
3. Lewy bodies
4. Hirano bodies
5. Tau proteins

Answer 22

Rosenthal fibres

Rosenthal fibers appear on H&E stained sections as brightly eosinophilic carrot-shaped or corkscrew-like
structures. Rosenthal fibres are alterations in astrocytic processes and provide a diagnostic signature of Alexander’s leukodystrophy.

These distinctive structures are present in association with longstanding gliosis as is seen around cavities in the CNS, in low grade, discrete astrocytomas such as pilocytic astrocytomas, and in patients suffering from Alexander’s disease. Hirano bodies are oval to elongated rod-shaped, eosinophilic inclusions, which are few in normal elderly and high in people with Alzheimer’s disease.

Question 23

Which one of the following receptors is a ligand-gated cation channel?

Select one:
1. Noradrenaline
2. 5-HT 7
3. 5-HT 1 b
4. 5-HT 1a
5. 5-HT 3

Answer 23

5-HT 3

There are fourteen 5HT receptors; all are G-protein coupled apart from 5HT-3, which is a ligand-gated
cation channel. 5HT-1 group (5HT-1a, 5HT-1b, 5-HT-1d) are inhibitory and are negatively coupled to cyclic
AMP. 5HT-2 receptors (5HT-2a,2b,2c) are excitatory and act through the phospholipase C/inositol
phosphate pathway. 5HT-4, 5HT-5,5HT-6,5HT-7 receptors are positively coupled to Cyclic AMP and are
thus excitatory.

Question 24

Tryptophan is the precursor of which of the following neurotransmitters?

Select one:
1. Noradrenalin
2. Dopamine
3. Adrenalin
4. Serotonin
5. Acetylcholine

Answer 24

Serotonin

Tryptophan –> 5 hydroxy l-tryptophan –> serotonin.

Question 25

Which of the following regions in the brain is predominantly cholinergic?

Select one:
1. Dorsal raphe
2. Median raphe
3. Substantia nigra
4. Locus coeruleus
5. Nucleus basalis of Meynert

Answer 25

Nucleus basalis of Meynert

The ascending system of cholinergic neurons originating in the reticular formation and the cholinergic cells in the nucleus basalis of Meynert are the major locations of cholinergic neurons in the brain.

Question 26

Which one of the following is the rate-limiting step in the synthesis of dopamine?

Select one:
1. Dopamine beta Hydroxylase
2. Choline acetyltransferase
3. Catechol o methyl transferase
4. Phenyl ethanolamine N-Methyltransferase
5. Tyrosine Hydroxylase

Answer 26

Tyrosine Hydroxylase

The rate-limiting step in the biosynthesis of dopamine is tyrosine hydroxylase, which converts tyrosine into
L-DOPA. The rate-limiting step in the biosynthesis of serotonin is tryptophan hydroxylase. The enzyme,
dopamine ß-hydroxylase, converts dopamine to noradrenaline. Phenylethanolamine-N-methyl transferase is involved in the conversion of noradrenaline to epinephrine. Choline acetyltransferase is involved in the biosynthesis of ACh.

Question 27

Supraspinal analgesia related to opioid release is mediated by

Select one:
1. Mu receptors
2. Nicotine receptor subunits
3. Kappa receptors
4. Sigma receptors
5. Delta receptors

Answer 27

Mu receptors

The general role of the endogenous opioids includes the regulation of pain (supraspinal and spinal analgesia), anxiety, and memory.

Question 28

Which one of the following is an incorrect pairing of the disease condition and the primary neurotransmitter that is abnormal in the diseases?

Select one:
1. Noradrenalin-depression
2. Dopamine - Alzheimer’s dementia
3. GABA- epilepsy
4. Dopamine- Schizophrenia
5. Serotonin-anxiety

Answer 28

Dopamine - Alzheimer’s disease

Dopamine is implicated in both schizophrenia and Parkinson’s disease. Glutamate is implicated in many
neurodegenerative disorders while GABA is implicated in epilepsy. Both noradrenaline and serotonin are
relevant for depression and anxiety. Acetylcholine is more relevant than dopamine for Alzheimer’s
dementia. Please note that the explanation here is an over-simplification - most neuropsychiatric disorders
include a generalised disturbance in multiple neurotransmission systems.

Question 29

Which of the following best describes D2 receptor?

Select one:
1. Presynaptic inhibitory receptor
2. Intranuclear receptor
3. Hetero-receptor
4. Auto-inducing receptor
5. Rosette shaped

Answer 29

Presynaptic inhibitory receptor

Most neurotransmitters inhibit their own release through auto- receptors. Dopamine inhibits its own release through D2 autoreceptors.

Question 30

The principal location of noradrenergic neuronal cell bodies in the CNS is

Select one:
1. Raphae nucleus
2. Nucleus basalis of meynert
3. Caudate and putamen nucleus
4. Locus coereleus
5. Hippocampus

Answer 30

Locus coereleus

The principal location of noradrenaline is the locus coereleus. The principal location of acetylcholine is in
the cell bodies in the nucleus basalis of Meynert with axons innervating the hippocampus. The neurones
containing 5-HT are located in the midbrain and brain stem median raphe nuclei.

Question 31

An enzyme involved in synthesis of acetylcholine is

Select one:
1. Choline acetyl transferase
2. Dopa hydroxylase
3. Acetylcholinesterase
4. Butyrylcholinesterase
5. Mono amine oxidase

Answer 31

Choline acetyl transferase

Cortical choline acetyl transferase (ChAT) is reduced to a greater extent (85%) in patients with
hallucinations in Lewy body dementia than in those without hallucinations (50%). This is more pronounced
in parieto-temporal regions, hippocampus and entorhinal cortex. As a consequence, brain acetylcholine levels are reduced in DLB similar to Alzheimer’s. This may partially explain the altered sleep-wake patterns seen in DLB and also the response of hallucinations to acetylcholinesterase inhibitors.

Question 32

Which of the following best fits GABA-A receptor?

Select one:
1. G protein coupled
2. Ligand dependent regulator of nuclear transcription
3. Metabotropic
4. Receptor with intrinsic enzyme activity
5. Ionotropic

Answer 32

Ionotropic

GABA A receptors are Ionotropic and can mediate postsynaptic inhibition

Question 33

The Nucleus of Meynert is a prominent site of localization for which neurotransmitter in the brain?

Select one:
1. GABA
2. Norepinephrine
3. Serotonin
4. Acetylcholine
5. Dopamine

Answer 33

Acetylcholine

Acetylcholine is localised to an ascending system of cholinergic neurons originating in the reticular
formation and nucleus basalis of Meynert.

Question 34

Which one of the following acts as a fast acting excitatory neurotransmitter?

Select one:
1. 5-hydroxytryptamine
2. Muscarinic Acetylcholine receptors
3. Dopamine
4. Glutamate
5. Noradrenaline

Answer 34

Glutamate

Receptors for neurotransmitters can be either

1. Directly coupled to an ion channel (ionotropic receptors)and so concerned with fast transmission Eg GABA-A, Nicotinic type of Ach receptors, N-Methyl-D-aspartate type of glutamate receptors). Glutamate is an example of a fast acting excitatory neurotransmitter where the receptors (NMDA) are directly linked to a sodium channel. Activation of the GABA-A receptor, which is linked to a chloride channel, results in an influx of chloride ion into the neurone causing hyper polarisation.
2. Coupled to an intracellular effector system through G-Protein (Metabotropic receptors) and so
   responsible for slow neurotransmission (dopamine, nor adrenaline, most 5-HT and muscarinic Ach
   receptors).

Question 35

Which of the following is a rosette shaped receptor?

Select one:
1. NMDA receptors
2. Beta adrenergic receptors
3. Thyroid hormone receptors
4. Alpha adrenergic receptors
5. Serotonin 5HT2 receptors

Answer 35

NMDA receptors

The GABA-A receptor’s structure is typical of most ligand-gated (ionotropic) receptors [‘doughnut with a
hole in the centre’ or ‘rosette’ shaped]. It is made up of five protein subunits arranged in a circular fashion.
This channel opens up when GABA binds to the recognition site. Each protein subunit is made of
membrane-spanning aminoacid chains (each traversing the cell membrane four times). A large N-terminal at the extracellular end mediates GABA-channel interactions. In the middle of the string is a large intracellular loop of amino acids with four sites where phosphorylation occurs. NMDA is also an ionotropic receptor with rosette shape.

Question 36

The most abundant neurotransmitter in the median raphe nuclei is

Select one:
1. Noradrenaline
2. GABA
3. Acetylcholine
4. Glycine
5. Serotonin

Answer 36

Serotonin

Serotonin transmission from the median raphe nuclei provides rich projections to the frontal cortex.

Question 37

The effects of magic mushroom are very similar to those of

Select one:
1. Cannabis
2. LSD
3. Cocaine
4. Methadone
5. Heroin

Answer 37

LSD

Many hallucinogens occur naturally in ‘magic mushrooms’, datura or ‘angel’s trumpet’ (atropine-like effects), mescaline and DMT (dimethyltryptamine). Magic mushrooms contain two hallucinogenic substances: psilocin and psilocybin. Psilocybin gets converted to psilocin and acts similar to LSD, although it is about 100 times less potent than the synthetic LSD itself. The most popular hallucinogen in current use is the synthetic drug LSD.

Question 38

The enzyme involved in catabolism of GABA is

Select one:
1. Transferase
2. Transaminase
3. Decarboxylase
4. Oxidase
5. Hydroxylase

Answer 38

Transaminase

The breakdown enzyme involved in GABA metabolism is GABA transaminase.