Neurobiology of Disease 10 Flashcards
(159 cards)
1
Q
Fill in the gaps relating to the gut-brain axis. (5)
There is a …….directional communication between the ………………… and ………………… nervous systems, linking ………………….. and …………………. centres of the brain with peripheral intestinal functions.
A
bi
central
enteric
emotional
cognitive
2
Q
The enteric nervous system has about 600 million neurones, which facilitate what four general functions of the GI tract? (4)
A
- Motor
- Sensory
- Absorptive
- Secretory
3
Q
Apart from the central and enteric nervous systems, name another division of the nervous system, along with a neuroendocrine pathway which play a role in the gut-brain axis. (2)
A
Autonomic nervous system (vagus nerve)
HPA axis
4
Q
Give five general types of ‘pathway’ which may facilitate communication between the gut and the brain. (5)
A
- Circulation
- Metabolic pathways
- CNX (vagus)
- Endocrine pathways
- Immune pathways
5
Q
Give four general types of molecules that can facilitate communication between the gut and the brain. (4)
A
Neurotransmitters
SCFAs
Indoles
Metabolites
6
Q
What is bottom-up signalling, when referring to the GBA? (1)
Give three neural pathways that can facilitate bottom-up signalling. (3)
A
Signals arise from lumen of GI tract and go to CNS (afferent signalling)
- Enteric nervous system
- Spinal nerves
- Vagus nerve
7
Q
Give two direct routes of communication in the GBA. (2)
A
Vagus nerve
Bloodstream
8
Q
Give three indirect ways in which the gut may communicate with the brain in the GBA. (3)
A
- Immune activation
- Altered intestinal permeability
- Entero-endocrine signalling
9
Q
Give six general brain processes or conditions which may be contributed to by gut dysbiosis. (6)
A
- Neuroinflammation
- Brain development
- Psychiatric disorders
- Autism
- Anxiety-depressive behaviours
- Neurodegeneration
10
Q
Neural and circulatory lines of communication in the GBA can allow the brain to influence the activities of intestinal functional effector cells.
Name five intestinal functional effector cells which may be influenced by the brain. (5)
A
- Immune cells
- Epithelial cells
- Enteric neurones
- Smooth muscle cells
- Enterochromaffin cells
11
Q
Give six examples of neurotransmitters that can be produced by gut microbiota. (6)
A
- GABA
- Serotonin
- Melatonin
- Histamine
- Dopamine
- Acetylcholine
12
Q
Give two molecules that can be produced by gut microbiota that can cause and affect inflammation. (2)
A
- Nitrate/nitrite/NO
- Hydrogen sulphide
13
Q
Apart from neurotransmitters and inflammatory mediators, give another type of molecule which is produced by the gut microbiota, and can directly influence the brain. (1)
A
Short chain fatty acids
14
Q
True or false? Explain your answer if appropriate. (1)
The gut microbiota is solely made up of many different species of bacteria.
A
False - also made up of viruses, fungi, yeast, and bacteriophages
15
Q
Name the four dominant phyla of bacteria making up the gut microbiota. (4)
A
- Actinobacteria
- Bacteroidetes
- Firmicutes
- Proteobacteria
16
Q
Actinobacteria is one of the dominant phyla of bacteria making up the gut microbiota.
Give an example of an actinobacteria. (1)
Is this bacteria gram positive or gram negative? (1)
A
Bifidobacterium
Gram positive
17
Q
Bacteroidetes is one of the dominant phyla of bacteria making up the gut microbiota.
Give an example of a bacteroidetes. (1)
Is this bacteria gram positive or gram negative? (1)
A
Bacteroides
Gram negative
18
Q
Firmicutes is one of the dominant phyla of bacteria making up the gut microbiota.
Give four examples of firmicutes bacterial species. (4)
Are these bacteria gram positive or gram negative? (1)
A
Clostridium
Staphylococcus
Enterococcus
Lactobacillus
These are gram positive
19
Q
Proteobacteria is one of the dominant phyla of bacteria making up the gut microbiota.
Give three examples of proteobacteria species. (3)
Are these bacteria gram positive or gram negative? (1)
A
Escherichia coli (E.Coli)
Salmonella
Helicobacter
These are gram negative bacteria
20
Q
In general, give three ‘good’ bacteria for the gut microbiome. (3)
A
- Bifidobacteria
- Escherichia coli
- Lactobacilli
21
Q
In general, give three ‘bad’ bacteria for the gut microbiome. (3)
A
- Campylobacter
- Enterococcus faecalis
- Clostridium dificile
22
Q
How does campylobacter affect the gut? (1)
A
Most common bacterial cause of diarrhoeal illness, usually from food poisoning
23
Q
How does Clostridium difficile affect the gut? (1)
A
Causes diarrhoea and colitis
24
Q
Describe why the gut brain axis particularly affects serotonergic neurotransmission. (2)
A
More than 90% of the body’s serotonin is synthesised by the gut microbiota
It then travels to the brain and unbound 5HT can cross the BBB
25
Give a pathogenic role of serotonin in the following locations. (2)
a) brain
b) gut
a) emotional distress/depression
b) IBS
26
Complete the sentence relating to the gut brain axis and SCFAs. (3)
Short chain fatty acids produced by the gut microbiota can cross the ...................... and influence ....................... and ..........................
blood brain barrier
neuroinflammation
neurogenesis
27
Give two GBA species which can affect BDNF. Describe how these species affect BDNF. (2)
Bifidobacteria can increase BDNF in hippocampus
Lactobacillus can increase BDNF expression in the brain
28
How do prebiotics affect BDNF? (1)
Prebiotics can increase BDNF levels in the hippocampus
29
Give a GBA species that can secrete acetylcholine. (1)
Lactobacillus
30
Give four GBA species which can secrete serotonin. (4)
- Candida
- Streptococcus
- Escherichia coli
- Enterococcus
31
Give 2 GBA species which can secrete dopamine. (2)
- Bacilli
- Serratia
32
Which kind of receptor do short chain fatty acids act on in the gut and brain? (1)
Give three examples of these receptors. (3)
GPCRs
GPR109
GPR41
GPR43
33
Which cell type in the gut is able to respond to microbiota products and communicate with the brain? (1)
Enteroendocrine cells
34
Give seven peptides/metabolites that are secreted by enteroendocrine cells in response to the gut microbiota, and are important for signalling in the gut-brain axis. (7)
- Serotonin
- SST (somatostatin)
- GLP-1 (glucagon-like peptide 1)
- GLP-2 (glucagon-like peptide 2)
- PYY (Peptide YY)
- GIP (glucose-dependent insulinotropic peptide)
- CCK (cholecystokinin)
35
Predominantly in which part of the GI tract do enteroendocrine cells react to the gut microbiota and release peptides to communicate with the brain? (1)
Large intestine
36
Give eight factors that can affect the composition of the gut microbiome. (8)
- Diet
- Environment
- Antibiotics
- Aging
- Probiotics
- Exercise
- Mode of delivery
- Stress
37
Complete the sentence relating to the gut microbiome. (2)
The initial microbiota is acquired ......................, and microbiota stability peaks .........................
at birth
in adulthood
38
True or false? Explain your answer if appropriate. (1)
The initial gut microbiome is shaped by a variety of both intrinsic and environmental factors.
True
39
True or false? Explain your answer if appropriate. (1)
Once the gut microbiome reaches its peak stability in adulthood, the composition remains constant and is unable to change later in life.
False - microbiome maintains flexibility to adjust to environmental or dietary changes
40
Evidence for the influence of the gut microbiota on brain physiology has surfaced mostly from studying germ-free animals.
Describe how neurophysiology is altered in germ-free animals in the following domains. (5)
a) myelination
b) microglia and neuroinflammation
c) blood-brain-barrier
d) neurogenesis
e) a-synuclein
a) increased oligodendrocyte gene expression and myelination in prefrontal cortex
b) altered microglial gene profile with altered cell proportions and an immature phenotype
c) decrease in tight junction protein expression and decrease in BBB permeability
d) increase in hippocampal and amygdala volume
e) Less accumulation of a-synuclein in the brain
41
Briefly describe how environmental stress is able to alter the gut microbiome. (2)
Environmental stress activates HPA axis,
which releases cortisol, and cortisol affects gut microbiome.
42
Give two ways in which cortisol affects the gut brain axis. (2)
- cortisol alters composition of gut microbiome
- and alters communication mechanisms between gut and brain
43
Cortisol is able to impact the gut brain axis by altering communication mechanisms between the gut and the brain.
Give two ways that cortisol can alter communication mechanisms in the GBA. (2)
- Altered gut permeability
- Altered inflammatory pathways
44
There is a prominent gradient of 'environmental' conditions along the length of the GI tract, which determines the density and diversity of microbial species found in a given region.
Give four environmental factors which form gradients throughout the GI tract. (4)
- pH
- oxygen
- Antimicrobial peptides
- Bile salts
45
In relation to the gut microbiome, is there more bacteria at the proximal or distal regions of the GI tract? (1)
Distal regions
46
There are two large factors of individual gut microbiome bacteria which determine their effects/outcome on the brain.
Which two factors are they? (2)
- Location of the microbiota within the GI tract
- Specific chemicals produced by the bacteria
47
True or false? Explain your answer if appropriate. (1)
Changes in the gut microbiome take place over long periods of time (months-years).
False - microbiota composition can fluctuate and change over relatively short periods of time (days)
48
True or false? Explain your answer if appropriate. (1)
The microbiome composition changes between individuals, and also over time.
True
49
Very briefly describe how the microbiome is altered with ageing. (1)
Some specific species are decreased with age and others are increased.
50
Describe briefly how the microbiome composition can be associated with healthy/unhealthy ageing. (1)
Increase/decrease in certain species of bacteria can be associated with healthy/unhealthy ageing
51
Are changes in gut microbiome composition thought to be a cause or a consequence of ageing? (1)
It is currently unknown
52
Infection of the intestine with Campylobacter jejuni induces nuclear c-Fos protein expression in which 6 brain regions? (6)
What does c-Fos expression indicate, and what does it suggest about the gut microbiota? (2)
- Lateral parabrachial nucleus
- Locus coeruleus
- Paraventricular nucleus of the hypothalamus
- Amygdala
- Stria terminalis
- Insular cortex
c-Fos expression indicates neuronal activity
suggests that gut microbiota is able to impact brain activity and function
53
Describe how lipopolysaccharide may be the link between the gut microbiota and Alzheimer's disease. (4)
LPS is released predominantly from the gut bacteria
LPS can be absorbed from the intestine and get into the blood stream
LPS then transported to brain
LPS levels shown to be altered (usually raised) and location of LPS altered in Alzheimer's disease
54
Lipopolysaccharide levels and location are shown to be altered in Alzheimer's disease, connecting the gut microbiome to AD.
Give two brain regions in particular where there may be higher levels of LPS in Alzheimer's disease. (2)
- Hippocampus
- Neocortex
55
Lipopolysaccharide levels and location are shown to be altered in Alzheimer's disease, connecting the gut microbiome to AD.
Give two proteins which are colocalised with LPS in the brain. (2)
- Amyloid beta (plaques)
- E.Coli proteins (and maybe E.Coli itself)
56
Given that the gut microbiome has been shown to impact Alzheimer's pathology, suggest two novel treatments which could potentially attenuate the AD phenotype. (2)
What are trials currently showing regarding these treatments? (1)
Antibiotics
Probiotics
Trials promising so far in terms of improved symptoms.
57
Give four experimental techniques that are currently being used to investigate the gut-brain axis. (4)
- Germ free animals
- Probiotics
- Antibiotics
- Infection with microbiota
58
Describe the changes seen in germ-free animals in terms of the following domains. (5)
a) neurotransmitters
b) HPA restrain stress response
c) social behaviours
d) anxiety-like behaviour
e) motor and rearing activity
a) altered expression and turnover
b) exaggerated HPA stress response
c) impaired social behaviours
d) altered anxiety-like behaviour
e) increased motor and rearing activity
59
Studies using germ-free animals to investigate the gut-brain axis often see alterations in neurological functioning and behaviour patterns.
How can we be sure that these changes are due to the animal being germ-free? (1)
Anomalies are restored after colonisation in a bacterial species-specific manner
60
An experiment gave aged mice either a faecal transplant from an old mouse or a faecal transplant from a young mouse.
Describe the effects of giving aged mice a young transplant compared to giving them an old transplant. (1)
What can we conclude about the microbiota and ageing? (1)
Those with a young transplant did not show age-associated behavioural deficits.
We can conclude that microbiota composition affects brain functioning associated with ageing.
61
An experiment gave aged mice either a faecal transplant from an old mouse or a faecal transplant from a young mouse.
Give 6 changes seen in mice with a young transplant, compared to mice with an old transplant. (6)
Give specific examples of three of these changes. (3)
- Altered behaviour (less age-related deficits)
- Restored metabolites
- Altered microbiota composition
- Decreased microglial inflammation (reduced hippocampal activated microglia)
- Altered microglial sensome (altered microglial gene expression)
- Decreased peripheral inflammatory cells and cytokines (reduced IL-10)
62
Transgenic mice are used to model Alzheimer's disease.
What effect would you expect to see if a wild type microbiome was transplanted in AD mice, in terms of the following domains? (3)
a) morris water maze
b) Ab-42 load
c) synaptic function
a) better performance on MWM (increased time in target quadrant and increased platform crossings)
b) potentially a reduced Ab load
c) potentially restored synaptic function
63
In mouse models of Alzheimer's disease, a wild type microbiome has been shown to restore synaptic function.
They showed this by doing a western blot of 2 proteins that indicate synaptic function.
Give two proteins that they could have measured. (2)
- PSD-95 (post synaptic density protein)
- Synapsin I
64
An experiment looked at the effects of diet on Alzheimer's phenotype in APPNL-f knock-in mice (mutations in APP gene).
How did a high-fat diet alter spatial learning on the Morris water maze? (1)
Impaired spatial learning (longer escape latency)
65
An experiment looked at the effects of diet on Alzheimer's phenotype in APPNL-f knock-in mice (mutations in APP gene).
How did a high-fat diet alter levels of synaptic markers in AD mice? (1)
Reduced synaptic markers (PSD95)
66
An experiment looked at the effects of diet on Alzheimer's phenotype in APPNL-f knock-in mice (mutations in APP gene).
How did a high-fat diet alter amyloid-b deposition in the brain? (1)
Which particular brain region was this seen in? (1)
Increased amyloid b deposition
in hippocampus
67
An experiment looked at the effects of diet on Alzheimer's phenotype in APPNL-f knock-in mice (mutations in APP gene).
How did a high-fat diet alter microglial activation in the brain? (1)
Which particular brain area was this seen in? (1)
More microglial activation
in hippocampus
68
Suggest how a high-fat diet may alter Alzheimer's phenotype in mice. (1)
Describe how this would happen. (2)
HFD exacerbates Alzheimer's phenotype
- HFD alters microbiome
- which interacts with risk genes to exacerbate phenotype
69
Describe a piece of evidence that the gut-brain axis may be involved in autism. (4)
Can induce autism in offspring by causing immune activation in mothers (eg. using poly I:C)
However by treating mothers with Bacteroides fragilis, offspring do not display autism-like behavioural abnormalities
Offspring from immune activated mothers treated with Bacteroides show less anxiety in open field test (increased centre entries, increased centre duration)
Compared to offspring from immune activation mothers without Bacteroides treatment
70
Give some examples of probiotic supplements. (10)
Yoghurt
Sourdough bread
Kefir
Kombucha
Pickled vegetables
Tempeh
Miso soup
Sauerkraut
Kimchi
Natto
71
Give some examples of prebiotic supplements. (13)
Bananas
Oatmeal
Asparagus
Jerusalem artichokes
Dandelion greens
Leeks
Garlic
Onions
Apple skin
Chicory root
Beans
Berries
Legumes
72
How might Belgian and German beers be related to the gut microbiome? (1)
Some beers (and also non-alcoholic equivalents) are able to alter the composition of the gut microbiome, as they contain live probiotic yeasts.
73
True or false? Explain your answer if appropriate. (1)
The gaseous neurotransmitters (NO and CO) are the oldest types of neurotransmitter to be discovered.
False - they are relatively newly-discovered neurotransmitters (1990s)
74
In which part/system of the body was nitric oxide first discovered as a signalling molecule? (1)
Blood vessels
75
Give five criteria that should be met for a molecule to be considered a neurotransmitter. (5)
- Synthesis on demand
- Storage in synaptic vesicles
- Release by exocytosis
- Actions at receptors on postsynaptic membrane
- Inactivation/reuptake mechanisms
76
Nitric oxide is often described as labile, or unstable.
Which property of NO makes it unstable? (1)
It is a free radical, which makes it highly reactive
77
What is the approximate half life of NO when it is in a tissue? (1)
100ms
78
Is nitric oxide synthesised and stored in pools until required, or is it synthesised on demand? (1)
On demand
79
Why are there no storage pools of NO in neurones? (2)
- NO is membrane permeable (so would diffuse out of vesicles and cells)
- NO is reactive
80
True or false? Explain your answer if appropriate. (1)
Nitric oxide is released from presynaptic neurones via exocytosis into the synapse.
False - NO diffuses across the membrane as it is membrane permeant
It would not be stored in vesicles for exocytosis because it would just diffuse out of them
81
True or false? Explain your answer if appropriate. (1)
NO only acts very locally at synapses in direct apposition to where it was released.
False - NO diffuses rapidly from site of production or release
However still only signals over a short range
82
Describe how nitric oxide acts on postsynaptic neurones or tissues after it is released from a cell. (2)
Diffuses into target cell
and does not act on cell surface receptors
83
Complete the sentence related to nitric oxide. (1)
Given the unique properties of NO as a neurotransmitter, it is perfectly suited to ........................ neurotransmission.
Short-range
84
Give two ways that nitric oxide is removed/inactivated in a tissue. (2)
Superoxide ions
Haemoglobin
85
Give the equation which represents removal of nitric oxide from a tissue using superoxide ions. (1)
O2- + NO = ONOO- (peroxynitrite)
86
Superoxide ions can inactivate/remove NO from tissues.
What type of molecule is superoxide? (1)
Reactive oxygen species and free radical
87
Superoxide ions can inactivate/remove NO from tissues.
Name the product formed from this inactivation mechanism. (1)
Peroxynitrite
88
The five criteria that a molecule should meet to be considered a neurotransmitter are:
- Synthesis on demand
- Storage in synaptic vesicles
- Release by exocytosis
- Actions at receptors on postsynaptic membrane
- Inactivation/reuptake mechanisms
Which of these criteria does NO meet? (1)
Is it a neurotransmitter? (1)
- Synthesis on demand (YES)
- Storage in synaptic vesicles (NO)
- Release by exocytosis (NO)
- Actions at receptors on postsynaptic membrane (NO)
- Inactivation/reuptake mechanisms (YES)
Either NO is not a neurotransmitter, or it is and we should have more flexible criteria.
89
A lot of the research looking into nitric oxide signalling is done by looking at what cellular component/protein? (1)
Why is this the case? (2)
Done by investigating nitric oxide synthase
- no antibodies against NO gas
- no NO receptors for agonism/antagonism
90
Name the three main isoforms of nitric oxide synthase, and for each isoform, give two alternative names. (3)
Suggest another isoform which has been suggested to be present, but is not well-characterised. (1)
neuronal NOS (nNOS, NOS-I)
inducible NOS (iNOS, NOS-II)
endothelial NOS (eNOS, NOS-III)
mitochondrial NOS (mtNOS)
91
True or false? Explain your answer if appropriate. (1)
Regarding nitric oxide synthase isoforms, nNOS is only found in neurones, and eNOS is only found in endothelial cells.
False - despite the names suggesting otherwise, the location of NOS isoforms is actually quite flexible
92
Nitric oxide synthase produces nitric oxide.
Give the equation describing the production of NO by NOS. (1)
L-arginine + O2 = L-citrulline + NO
93
Give the amino acid which acts as a substrate for NO production. (1)
Name the chemical process which this amino acid undergoes during the reaction to produce NO. (1)
L-arginine
Oxidation
94
All isoforms of nitric oxide synthase require what protein to be present in order to function? (1)
Calmodulin
95
Give two nitric oxide synthase isoforms which require calcium to be present in order to function. (2)
nNOS
eNOS
96
Apart from calcium and calmodulin, nitric oxide synthase is also highly regulated by a number of other molecules. The enzyme contains recognition sites for these molecules.
Give five molecules which are able to regulate NOS. (1)
What category of molecules do they all belong to? (1)
- NADPH (nicotinamide adenine dinucleotide phosphate)
- Flavine adenine dinucleotide (FAD)
- Flavin mononucleotide (FMN)
- Tetrahydrobiopterin
- Heme
These are all electron donors
97
Describe the main method by which nitric oxide has downstream effects in cells. (2)
Activates soluble guanylyl cyclase (400-fold activation)
This increases cGMP in the cytoplasm of cells
98
NO has downstream effects by increasing cGMP in cells.
Give four downstream effects of increasing cGMP in the cytoplasm of cells. (4)
- cGMP-dependent protein kinase (PKG)
- Activation of non-selective cation channels
- Decreased intracellular calcium
- Increased PDE (phosphodiesterase; which breaks down cGMP)
99
Nitric oxide has effects on cells by activating soluble guanylyl cyclase and increasing cGMP levels.
Give a physiological mechanism of terminating this response which occurs in cells. (1)
Phosphodiesterase breaks down cGMP
100
Give an event which occurs in the CNS, which may be coupled to the production of NO by nNOS. (1)
Why are these events coupled? (1)
Glutamate binding to NMDA receptors
Because this results in calcium influx into the cell, which activates nNOS
101
Give two other neurotransmitters that are co-released with nitric oxide in the blood vessels of salivary glands in the PNS. (2)
What effects do these three neurotransmitters have together? (1)
- ACh
- VIP
Relaxation of vascular smooth muscle
102
Nitric oxide acts as a co-transmitter which what other NT in nerves of the portal vein. (1)
Give the general type of nerve that this would be. (1)
ATP
NANC nerve (non-adrenergic, non-cholinergic nerve)
103
Nitric oxide neurotrasmission is used in many different locations throughout the brain.
Give two brain regions in particular which contain high densities of NOS and show high levels of nitroxigenic neurotransmission. (2)
- Cerebellum
- Accessory olfactory bulb
104
Give six roles of nitric oxide signalling in the brain. (6)
- Regulation of excitability
- Regulation of firing
- LTP/LTD
- Learning and memory
- Neurotransmitter release (increase and decrease)
- Development
105
Why is it bad for excess levels of NO to be present in the brain? (1)
High levels are neurotoxic
106
What is the role of nitric oxide in the cerebral vessels? (1)
Vasodilator
107
What is the role of nitric oxide in the salivary glands? (1)
Vasodilator (in blood vessels of salivary glands)
108
What is the role of nitric oxide in the trachea and respiratory system? (1)
Bronchodilation
109
What is the role of nitric oxide in the portal vein? Specifically, the rabbit portal vein? (1)
Vasorelaxation
110
Give two pieces of evidence that nitric oxide neurotransmission is important for the function of the pyloric sphincter. (2)
- nNOS-/- mice show dilated stomach and pyloric hypertrophy
- NANC relaxation is abolished in nNOS-/- mice and restored by NO donors
111
How might nitric oxide be involved in the GI tract? (1)
Used as a transmitter by myenteric neurones
112
Give a role of nitric oxide in the urinary bladder. (1)
Regulation of outflow
113
Where exactly is nitric oxide (or more specifically, nNOS) found in the penis? (2)
- Neurones of corpora cavernosae
- Neurones innervating blood vessels of penis
114
What is the role of nitric oxide in the penis? (1)
Erection (via vasodilation)
115
Give two pieces of evidence supporting the fact that nitric oxide plays a role in penile erection. (2)
Electrical stimulation of penile nerves results in erection, and this effect is blocked by NOS inhibitors
Sildenafil (viagra) is a type 5 phosphodiesterase inhibitor and is used as a therapy in erectile dysfunction
116
An experiment measured how nitric oxide may be involved in regulating blood flow in the pig salivary gland.
Normal stimulation of parasympathetic (ACh-containing) nerves resulted in vasodilation and therefore increased blood flow.
What did they see when L-NNA was added? (1)
Why was this effect seen? (1)
Blood flow could not increase when nerves were stimulated
This was seen because L-NNA is a NOS inhibitor and NO is required for vasodilation
117
An experiment measured how nitric oxide may be involved in regulating blood flow in the pig salivary gland.
Normal stimulation of parasympathetic (ACh-containing) nerves resulted in vasodilation and therefore increased blood flow.
What did they see when sodium nitroprusside (SNP) was added in addition to L-NNA? (1)
Why was this effect seen? (1)
Increased blood flow when nerves were stimulated
Because SNP is an NO donor which can overcome the effects of L-NNA (a NOS inhibitor)
118
Sodium nitroprusside (SNP) is an NO donor.
What is meant by an NO donor? (1)
It spontaneously breaks down to produce NO
119
NO is used as a co-transmitter with ACh and VIP in nerves of the salivary gland blood vessels.
Which general category of nerves use these three molecules as co-transmitters? (1)
Parasympathetic nerves
120
NANC nerves in the rabbit portal vein use what two molecules as cotransmitters for vasorelaxation? (2)
ATP
Nitric oxide
121
Describe a piece of supporting evidence for NANC nerves in the rabbit portal vein using both ATP and NO as co-transmitters. (3)
Addition of suramin, which blocks P2 purine receptors for ATP partly blocks the vasorelaxation response when NANC nerves are stimulated
L-NAME, which is a NOS inhibitor, blocks any remaining vasorelaxation response.
This also happens when the compounds are added in the reverse order.
122
Addition of a NOS inhibitor, L-NAME, to NANC nerves in the rabbit portal vein is able to greatly reduce, and maybe even abolish the neurogenic vasorelaxation response seen when NANC nerves are stimulated.
In experimental conditions, suggest how we can confirm that abolishment of the response is due to inhibition of NOS and a reduction in NO. (1)
Adding excess substrate (L-Arginine) to overcome NOS inhibition will restore vasodilation.
***This could also potentially be achieved by adding an NO donor such as sodium nitroprusside, however L-arginine was used in this particular experiment
123
How could we use immunohistochemistry to provide evidence that nitric oxide is used by nerves innervating the rabbit portal vein to induce vasodilation? (2)
What would the results show? (1)
HINT: the lab have run out of antibodies against NOS, so we must use another way
Stain for NADPH diaphorase (enzyme used to transfer electrons from NADPH)
because nNOS exhibits NADPH diaphorase activity
we would see this present in muscle layers of blood vessels
124
Briefly describe four domains/ways of collecting evidence supporting the role of nitric oxide as a neurotransmitter. (4)
- Localisation of associated proteins (NOS, NADPH diaphorase)
- Agonists/antagonists of NOS and NO donors, and NANC neurotransmission
- Release of NO (can be measured by tissue probes)
- nNOS-/- mice
125
Give three pieces of evidence related to the localisation of proteins associated with nitric oxide, which supports the role of NO as a neurotransmitter in specific tissues. (3)
- nNOS immunolocalisation
- nNOS mRNA in situ hybridisation
- histochemical localisation of NADPH diaphorase
126
Give three pieces of evidence regarding NANC vasorelaxation and agonists/antagonists of NOS and NO donors, which support the role of nitric oxide as a neurotransmitter. (3)
NANC VASORELAXATION IS:
- blocked by NOS inhibitors (L-NAME; L-NNA)
- NOS inhibitor block reversed by L-arginine (NO substrate)
- vasorelaxation effects mimicked by NO donors (SNP)
127
Give five changes seen in nNOS-/- mice which provide evidence to support the role of NO as a neurotransmitter. (5)
- Decreased muscle relaxation
- Decreased cGMP levels
- Decreased neurophysiological response to nerve stimulation
- Abnormal resting potentials
- Reversal of effects by NO donors
128
Give four locations where nitric oxide acts as a co-transmitter with VIP. (4)
- Myenteric neurones
- Eye
- Salivary glands
- Cerebral arteries
129
Give a location where nitric oxide acts as a co-transmitter with ACh. (1)
Give another location where NOS is shown to be co-localised with ChAT, which suggests that NO/ACh co-transmission may also happen here. (1)
- Salivary glands
- Co-localisation in brainstem
130
Give a location where nitric oxide acts as a co-transmitter with ATP. (1)
Portal vein (rabbit portal vein in particular)
131
Give a location where nitric oxide acts as a co-transmitter with carbon monoxide. (1)
Myenteric neurones
132
Give a location where nitric oxide acts as a co-transmitter with glutamate. (1)
cerebellum
133
Give a location where nitric oxide acts as a co-transmitter with GABA. (1)
Cerebellum
134
Give a location where nitric oxide acts as a co-transmitter with somatostatin and neuropeptide Y. (1)
Corpus striatum
135
State the usual neuromodulatory role of nitric oxide. (1)
Modulates the outflow of other neurotransmitters (usually acts to increase neurotransmitter release)
136
Describe two pieces of experimental evidence supporting the fact that nitric oxide has a neuromodulatory function, and usually acts to increase neurotransmitter release. (2)
- NOS inhibitors suppress peptide outflow from parasympathetic nerves in salivary gland, pancreas, and intestine
- NO donors enhance, and NOS inhibitors reduce, basal release of ACh in the brain
137
Briefly describe how the product formed from superoxide removal of nitric oxide damages cells. (3)
Product formed is peroxynitrite
which can be classed as a reactive oxygen species
and interact with lipids, DNA, and proteins to cause oxidative injury
138
Briefly describe how the three isoforms of nitric oxide synthase may be stimulated/induced in stroke. (3)
- Brain ischaemia/reperfusion leads to transient stimulation of eNOS
- Energy depletion leads to cell depolarisation and release of glutamate, which activates nNOS by binding NMDARs
- Activated microglia and inflammatory cytokines activate iNOS
139
eNOS is briefly stimulated during stroke.
Describe how this might be an advantage and play a neuroprotective role after ischaemia. (1)
NO produced by eNOS dilates blood vessels and increases blood flow
(may also decrease neuronal apoptosis and platelet aggregation)
140
Describe how enhanced NO production by nNOS and iNOS during stroke damages the brain. (5)
- More superoxide produced to get rid of NO
- More peroxynitrite produced as a metabolic product of NO and O2-
- Peroxynitrite damages DNA, lipids, and proteins
- and also triggers PARP (polyADP-ribose polymerase) activation
- which can all lead to mitochondrial dysfunction and neurotoxicity
141
Fill the gaps relating to how nitric oxide may be related to Parkinson's disease. (2)
In a mouse model of PD induced by .................... (selective neurotoxin of dopaminergic nigrostriatal neurones), elevated levels of ....................... were demonstrated in the ventral midbrain and striatum.
This supports a role of NO in Parkinson's disease.
MPTP
nitrotyrosine
142
Describe a piece of evidence supporting a role of nitric oxide in Parkinson's disease, relating to nNOS knockout mice (which also applies to mice/primates treated with nNOS inhibitors). (1)
What does this piece of evidence suggest specifically about the role of NO in PD? (1)
nNOS knockout or nNOS inhibitors makes animals more resistant to MPTP-induced toxicity
this suggests that NO may have a pathogenic role in PD
143
Describe three postmortem findings in Parkinson's disease, which can provide evidence supporting a role of nitric oxide in Parkinson's disease pathology. (3)
- ROS and peroxynitrite mediated oxidative and/or nitrosative damage is seen
- Increased nitrotyrosine accumulation in Lewy bodies
- Increased nitrotyrosine accumulation and overexpression of nNOS in polymorphonuclear (immune) cells
144
Apart from nitric oxide, name another gaseous neurotransmitter. (1)
Carbon monoxide
145
Describe the stability and half-life of carbon monoxide, compared to nitric oxide. (2)
More stable
Relatively long half-life (36-137mins)
146
Why would you expect nitric oxide to be much more unstable and reactive than carbon monoxide? (1)
Nitric oxide is a free radical and carbon monoxide is not
147
Name the enzyme which produces carbon monoxide in the body. (1)
Heme oxygenase (HO)
148
Describe the reaction catalysed by heme oxygenase in the body to produce carbon monoxide. (2)
HO oxidises porphyrin ring of heme
to form biliverdin, Fe, and CO
149
When heme oxygenase produces carbon monoxide in the body, another enzyme must also be present.
Name this enzyme, and state its role/why its presence is required. (2)
Cytochrome P450 reductase
allows NADPH to act as an electron donor during the reaction
150
Name the three heme oxygenase isoforms that produce carbon monoxide in the body. (3)
State how each isoform is induced/activated.
HO1 - heat shock protein
HO2 - constitutive
HO3 - constitutive
151
HO1, an isoform of heme oxygenase, is described as a 'heat shock protein'.
Describe what is meant by this. (1)
It is induced by cellular stress
152
HO1, an isoform of heme oxygenase, is found in which location in the body? (1)
Concentrated in peripheral tissues, such as spleen and liver
153
HO2, an isoform of heme oxygenase, is found in which location in the body? (1)
Highly concentrated in the brain, and protein/mRNA highly localised in specific nerves
154
Briefly describe how the signalling molecule CO has its downstream effects in cells. (1)
Activates soluble guanylyl cyclase (5 fold)
155
NO and CO are both gaseous neurotransmitters, which have downstream effects by activating soluble guanylyl cyclase.
Compare the extent to with NO and CO activate sGC in cells. (1)
NO activates much more than CO
156
What is the main experimental method used to investigate CO signalling in the body? (1)
Heme oxygenase (HO) inhibitors
157
Give a location in the body where CO may play an important role in reproductive function as a neurotransmitter. (1)
Vas deferens
158
CO, as a neurotransmitter, plays an important role in the GI tract.
Describe two pieces of evidence that support the role of CO in the GI tract, and may also point to the specific role of CO. (2)
- HO2-/- mice show reduced NANC neurotransmission and cGMP levels in the intestine (reduced by about 50%)
- HO has been shown to be colocalised with nNOS in myenteric neurones
159
HO2 expression is dense in the brain, however we don't know much about the role of CO in the brain.
Give a role which has been suggested, and how CO may fulfil this role in the brain. (2)
LTP and memory
through cGMP
