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ACVD Exam > Cutaneous Sensation and Psychodermatology (including diseases and medications) > Flashcards

Cutaneous Sensation and Psychodermatology (including diseases and medications) Flashcards

1
Q

Where is the itch sensation limited to?

A

Skin, mucosa, and cornea

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2
Q

Describe Merkel cells

A

Light touch
Slow-adapting Aβ sensory fiber
Located along the stratum basale between keratinocytes
Also can be associated with hair

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3
Q
A

Meissner’s corpuscle

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4
Q

Describe Messiner’s corpuscle

A

Touch (dynamic skin deformation)
Rapidly-adapting Aβ sensory fiber

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5
Q
A

Merklel cell

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6
Q

Describe Ruffini corpuscle

A

Stretch
Slow-adapting Aβ sensory fiber

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7
Q
A

Pacinian corpuscle

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8
Q
A

Pacinian corpuscle

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9
Q

Describe Pacinian corpuscles

A

High pressure, vibration
Rapidly-adapting Aβ sensory fiber
Single non-myelinated nerve fiber enclosed by a multi-layer connective tissue capsule

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10
Q

Describe the sensation of hair follicles

A

Light touch, low-frequency vibration
All types of sensory fibers

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11
Q

What are the three intercommunicating plexuses of arteries and veins?

A

1) Deep plexus (interface of dermis and subcutis - some branches supply lower hair follicle and epitrichial sweat glands)
2) Middle plexus (level of the sebaceous gland and supplies arrector pili, middle hair follicle, and sebaceous glands)
3) Superficial plexus (capillary loops just below the epidermis - supplies upper hair follicle and epidermis)

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12
Q

Describe arterioles

A

endothelial cells surrounded by smooth muscle cells, most likely function as part of the resistance vessels in skin

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13
Q

If you wanted to stain Merkel cells on histopathology, what stain would you use?

A

CK20 (green)
IHC NSE (brown)

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14
Q
A

Ruffini corpusle

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15
Q
A

Potential new somatosensory organ in dogs
Non-encapsulated free nerve endings

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16
Q

What is one sentence that can describe how Merkel’s discs, Meissner’s corpuscles, Ruffini endings, and Pancinian corpuscles experience a finger moving over braille?

A

Each receptor sensors the same stimuli differently

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17
Q

Which type of nerve fibers typically respond to innocuous touch?

A

C fibers

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18
Q

Which type of nerve fibers typically respond to nociceptive touch?

A

Aδ fibers
C fibers

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19
Q

What is a dermatome?

A

An area of the skin supplied by one spinal nerve

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20
Q

What supplies the nerves of the skin of the head?

A

Cranial nerves

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21
Q

What supplies the nerves of the skin of the trunk and forelimbs?

A

Thoracic spinal nerves

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22
Q

What supplies the nerves of the hind limbs?

A

Pelvic spinal nerves

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23
Q

What are tylotrich hairs?

A

Large primary follicle surrounded by a ring of neurovascular tissue
Aδ fibers
Rapid
Associated with a tylotrich pad

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24
Q

What are the rapid adapting mechanoreceptors?

A

Pancinian corpuscle
Meissner corpuscle
Guard and down hairs
Tylotrich hairs

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25
Q

What are tylotrich pads?

A

Small, hairless, knob-like innervated structure on the haired skin of dogs and cats
Slow adapting mechanoreceptors

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26
Q

What are sinus hairs?

A

Hair with an endothelia blood sinus and a nearby Pancinian corpuscle

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27
Q

What are the slow adapting mechanoreceptors?

A

Merkel cell
Ruffini corpuscle
Sinus hair
Tylotrich pad

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28
Q

What do free nerve endings do?

A

They terminate in the dermis
Associated with “C fibers” and surrounded by Schwann cells
Pencillate (touch, temp, pain, itch)
Papillary (around hair, sense cold)

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29
Q

What do transient receptor potential channel (TRP)s sense?

A

pH
Chemical agents
Temperature
Osmolality

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30
Q

What does transient receptor potential ankyrin1 (TRPA1) do?

A

Sense cold and pungent taste (wasabi, horseradish, garlic, cinnamon)
Expressed on Aδ and c fibers

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31
Q

What does transient receptor potential melastatin 8 (TRPM8) do?

A

Sense cold, menthol, mint, and icilin

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32
Q

What is icilin?

A

A synthetic cooling agent that produces a strong sensation of cold in humans and animals

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33
Q

What does topical application of menthol and icilin activate?

A

Transient receptor potential melastatin 8 (TRPM8)

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34
Q

What does transient receptor potential vanilloid 1 (TRPV1) do?

A

Detects noxious heat and pain-producing substances like capsaicin

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35
Q

What does topical application of capsaicin activate?

A

Transient receptor potential vanilloid 1 (TRPV1)

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36
Q

What are transient receptor potentials?

A

A class of cationic channels that act as signal transducer by altering membrane potential or intracellular calcium (Ca2+) concentration
Sense heat, cold, and certain chemicals

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37
Q

Which cutaneous sensory receptors respond to touch?

A

Hair
Tactile disk
Meissner corpuscle
Ruffini corpuscle
Pancinian corpuscle

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37
Q

Which of the following mechanoreceptor has the smallest
receptive?

A

Merkel cell axon complex

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38
Q

Which cutaneous sensory receptors respond to heat, pain, and itch?

A

Heat receptor, nociceptor (transient receptor potentials)
Free nerve endings

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39
Q

What is the relative axon diameter and conduction velocity of Aβ/II nerve fibers?

A

Medium (but largest for cutaneous), medium

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40
Q

What is the relative axon diameter and conduction velocity of Aδ/III nerve fibers?

A

Small, medium

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41
Q

What is the relative axon diameter and conduction velocity of C/IV nerve fibers?

A

Smallest, slow

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42
Q

Which type of cutaneous sensory nerve fiver has the largest axon diameter?

A

Aβ/II

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43
Q

Which type of cutaneous sensory nerve fiver has the smallest axon diameter?

A

C/IV

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44
Q

Which cutaneous nerve fibers are myelinated?

A

Aβ/II and Aδ/III

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45
Q

What type of nerve fiber senses epicritic itch?

A

Aδ/III

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46
Q

What is epicritic itch?

A

Sharp, well-defined itch

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47
Q

What type of nerve fiber senses protopathic itch?

A

C/IV

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48
Q

What is protopathic itch?

A

Poorly localized, sometimes burning itch
Not spontaneous but hyper-responsive to minor stimuli

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49
Q

What is spontaneous itch?

A

Well-localized at the site of stimulation
Only persists briefly after stimulus is removed

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50
Q

Where are Aβ/II nerve fibers found?

A

Merkel cells
Meissner’s corpuscles
Ruffini endings
Pacinian corpuscles
Hair follicles

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51
Q

What do Aβ/II nerve fibers sense?

A

Non-noxious mechanical stimuli
Touch, pressure

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52
Q

Where are Aδ/III nerve fibers found?

A

Hair follicles
Free nerve endings

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53
Q

What do Aδ/III nerve fibers sense?

A

Noxious stimuli
Fast pain
Epicritic itch
Mechanical stimuli
Temperature

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54
Q

Where are C/IV nerve fibers found?

A

Hair follicles
Free nerve endings

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55
Q

What do C/IV nerve fibers sense?

A

Noxious stimuli
Slow pain (considered the classic pain receptor)
Temperature
Chemicals
Itch (main one for AD itch, primarily protopathic itch)

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56
Q

Do myelinated or unmyelinated nerves have faster conduction?

A

Myelinated (the signal is protected)

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57
Q

What is alloknesis?

A

Normally non-itchy stimulus causes an itch or scratching sensation
Associated with C fibers
Common in chronic atopic dermatitis

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58
Q

What is physiologic itch?

A

Short-lived response to a pruritogen

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59
Q

What is pathologic itch?

A

AKA neuropathic itch
A chronic, usually intense, itching sensation caused by damage to the nerves that transmit itch

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60
Q

What is referred itch?

A

Development of a focal area of pruritus during scratching of a different, primary pruritic site

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61
Q

What is conversion itch?

A

Change of a normal sensation like touch to itch

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62
Q

What is the pathway of cutaneous sensation to the brain?

A

Peripheral sensory neuron –>
goes up primary afferent neurons through dorsal root ganglion –>
synapses with secondary transmission neurons in dorsal horn –>
cross over to contralateral spinothalamic tract in spinal cord–>
goes up spinothalamic tract to thalamus in the brain –>
goes to sensory cortex of the cerebrum

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63
Q

What is the dorsal root ganglion?

A

A pseudounipolar neurons relay sensory information to the spinal cord through a characteristic bifurcating axon, which sends one projection to the periphery and the other into the spinal cord

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64
Q

What is the gate control theory of cutaneous sensation/pain/itch?

A

Theory proposes that the spinal cord contains neural structures that act as a gate to control the flow of pain signals from the body to the brain so the sensation of a noxious stimuli can be blocked by a non-noxious stimuli carried by nerve fibers that reach the brain before the painful input
- substantia gelatinosa cells
- central factors like anxiety and boredom may act to reduce or amplify

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65
Q

What causes itch on inflamed skin?

A

Infections
Ectoparasites
Allergies
Immune-mediated
Neoplasia

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66
Q

What causes itch on non-inflamed skin?

A

Neuropathic
Systemic
Psychogenic

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67
Q

What is a pruritogen?

A

Any substance/mediators that cause pruritus

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68
Q

Which are the main amines that are pruritogens?

A

histamine
serotonin

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69
Q

Which are the main neuropeptides that are pruritogens?

A

substance P
NGF

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70
Q

Which are the main proteases that are pruritogens?

A

KLKs
cathepsin S
tryptase/chymase
exogenous proteases (HDM, Staphylococcus sp., mucunain)

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71
Q

Which are the main cytokines that are pruritogens?

A

TSLP
IL-2
IL-4
IL-13
IL-31***
IL-33

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72
Q

What is a plant that can cause non-histaminergic itch?

A

Cowhage (Velvet beans) due to the protease mucunain

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73
Q

What are the differences between histaminergic vs non-histaminergic itch pathways?

A

Histaminergic is mediated by mast cells and basophils
Follow similar pathway skin –> DRG –> spinal cord –> brain but activate some different (and some overlapping) areas of the brain

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74
Q

What are the primary differences between acute and chronic itch?

A

Acute is histamine dependent and mediated through BNP/NPRA
Chronic is histamine independent and mediated through GRP/GRPR

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75
Q

On which receptor do cannabinoids primarily work?

A

TRPV1

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76
Q

What are the primary functions of histamine?

A

Neurotransmission
Itchiness
Contraction of airways
Dilation of blood vessels
Gastric acid secretion

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77
Q

Which histamine receptors are most important for itch?

A

H1*
H4

Newer generations of antihistamines are more H1 specific

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78
Q

What are H1 histamine receptors primarily involved in?

A

Acute allergic reactions
- itch
- bronchoconstriction
- vasodilation (potential hypotension)
Sleep disorders

79
Q

What are H2 histamine receptors primarily involved in?

A

Gastric acid secretion (increased)

80
Q

What are H3 histamine receptors primarily involved in?

A

Neurotransmitter modulation (only exist in the CNS)

81
Q

What are H4 histamine receptors primarily involved in?

A

Immunomodulation
- eosinophil shape, mast cells, chemotaxis
Itch

82
Q

Does histamine induce pruritus in dogs?

A

Maybe mild itch, esp higher doses according to some studies
- histamine, comp 48/80, anti-canine-IgE injected intradermally
Other study did not find effect
- histamine, serotonin, tryptase, substance P, IL-2 injected intradermally
But does definitely cause a wheal and flare

83
Q

What is compound 48/80?

A

A chemical that causes the non-IgE dependent release of histamine from mast cells

84
Q

Does substance P induce pruritus in dogs?

A

Unsure, a study did not find effect of substance P when injected intradermally
But it is known to cause neurogenic inflammation

85
Q

Where is substance P found in the cutaneous sensation pathway?

A
  • interaction between Mrgpr on mast cell and SP on afferent neuron
  • interaction between SP on afferent neuron and NK1 in dorsal horn
86
Q

What are the 3 pathways involved in neurogenic inflammation?

A

1) chemotaxis and activation
2) vasodilation, permeability, and adhesion
3) dendritic and T-cell priming

*substance P and CGRP involved in all 3

87
Q

What is the role of nerve growth factor (NGF) in itch associated with atopic dermatitis?

A
  • Increases cutaneous innervation in AD models
  • patients with AD have more nerve elongation factors like NGF
  • might contribute to the development of chronic pruritus
88
Q

What is nerve growth factor (NGF)?

A
  • neurotrophic factor essential for the survival and maintenance of primary afferent neurons and sympathetic neurons
  • inflammatory mediator associated with pain and itch
89
Q

Which cells in the skin produce nerve growth factor (NGF)?

A

Mast cells
Macrophages
Keratinocytes
Fibroblasts
T-cells

90
Q

What does Il-31 do to mouse dorsal root ganglion neurons?

A

promotes axonal growth of DRG neurons

91
Q

Which pruritogenic proteases are produced by keratinocytes?

A

Kallikreins (KLKs)
Cathepsin S

92
Q

Which pruritogenic proteases are produced by immune cells?

A

Cathepsin S
Tryptase
Chymase

93
Q

How do proteases cause pruritus?

A

by activating protease-activated receptors (PARs) on nerve endings and keratinocytes

94
Q

Which cytokine has been demonstrated to cause itch in dogs and cats?

A

IL-31 (acute, severe itch when injected)

95
Q

Which are the primary IL-31 producing cells in the skin?

A

CD3+CD4+ T cells (likely Th2 cells)

Keratinocytes express the mRNA, but maybe not the final protein in normal skin but maybe in the skin of humans and dogs with AD

96
Q

Which cells in the skin have IL-31 receptors?

A

Free nerve endings
Keratinocytes

(also in canine dorsal root ganglia)

97
Q

Which cell signaling pathways does IL-31 primarily activate?

A
  • JAK 1/2
  • STAT 1/2/5
    PI3K/AKT
98
Q

What is the role of IL-31 in feline atopic skin syndrome?

A

Unsure
Causes pruritus when injected
One study found no differences in systemic or cutaneous IL-31 expression between cats with allergic dermatitis and controls (Older, 2021)
Another study found circulating IL-31 was higher (Dunham, 2018)

99
Q

What is the itch-scratch cycle?

A

skin barrier disruption –>
release of cytokines, proteases, AMPs –>
interaction with immune cells (inflammation) –>
more release of neuropeptides, cytokines, and proteases –>
sensory dysfunction –>
signal to brain = scratch –>
cycle continues

100
Q

What is the role of transient receptor potential channels (TRPs) in the itch neuronal pathway?

A

Interaction of amines, neuropeptides, and cytokines with receptors in neurons causes the opening of TRP channels which leads to depolarization of neuronal membranes and causing itch sensation

101
Q

Which molecule is largely responsible for neurogenic inflammation in the skin?

A

Substance P

102
Q

What is neurogenic itch?

A

Itch induced by pruritogens in the absence of neural damage
Itch on inflamed skin

103
Q

What type of itch does canine syringomyelia cause?

A

Neuropathic itch

104
Q

What causes canine syringomyelia?

A

Exact etiology and pathogenesis are unknown
Thought to develop secondary to an obstruction of cerebrospinal fluid (CSF) flow at the level of the foramen magnum
Most frequently associated with Chiari-like malformation (CM)
Other documented causes include trauma and neoplasia

105
Q

What is Chiari-like malformation (CM) in dogs?

A

Mismatch in skull and brain size (brain too big and skull to small)
Blocks the foramen magnum and disrupts the flow of CSF

106
Q

What breed is predisposed to syringomyelia?

A

Cocker spaniels - genetically prone to Chiari-like malformation (CM)

107
Q

What is canine syringomyelia?

A

A neurological condition in dogs that causes fluid-filled cavities to develop in the spinal cord

108
Q

What are the clinical signs of canine syringomyelia?

A

“Phantom scratching” = Dysesthesia (spontaneous or evoked unpleasant sensation)
Maybe a result of alteration of sensory threshold potentially due to spongy degenerative changes to the spinal cord?

109
Q

5 yr CKCS

A

Syringomyelia

110
Q

What happens to substance P in CKCS with syringomyelia?

A

Significant difference of SP between symptomatic SM and control dogs
(No difference between symptomatic and asymptomatic)

111
Q

What type of itch is acral mutilation syndrome?

A

Neuropathic

112
Q

What causes acral mutilation syndrome in dogs?

A

Autosomal-recessive with incomplete penetrance
sensory neuropathy (diminution of pain perception)
SNP in GDNF

113
Q

What breeds has acral mutilation syndrome most frequently been reported in?

A

German short-haired pointer
English springer spaniel
English/French spaniel
English cocker spaniel

114
Q

German short-haired pointer, 4mo, sudden and intense licking and chewing causing trauma.

What gene would you test for a mutation?

A

GDNF

115
Q

Several months after having his tail docked, a dog presents with a nodule on the tip of the nail and intense tail biting (itch vs pain). What causes this condition?

A

Regenerative growth of nerves (neuroma)
Tail dock neuroma

116
Q

What is a radiculopathy?

A

a condition that occurs when nerve roots in the spine are damaged or compressed
may cause focal neuropathic itch/pain

117
Q

What is trigeminal trophic syndrome?

A

a rare condition resulting from self-trauma of the skin after peripheral or central injury to the trigeminal system (CN V)

118
Q

What is brachioradial pruritus?

A

a neurological condition that causes intense itching, pain, stinging, or tingling in the upper extremities, usually on the dorsolateral forearm (C5-C6)

119
Q

What is notalgia paresthetica?

A

a chronic sensory neuropathy that causes a localized itch or paresthesia in the mid-back, usually on the left side below the shoulder blade (T2-T6)

120
Q

How do you diagnose a radiculopathy?

A

Clinical manifestation, will be localized pain/itch
May have a history of trauma
Potential imaging (CT, MRI)
Will not be responsive to glucocorticoids (might be to gabapentin)

121
Q

Which virus can cause facial pruritus in cats?

A

Feline herpes virus
may be a combination of neurogenic (inflammatory) and neuropathic itch

122
Q

Why type of itch is acral lick dermatitis typically considered?

A

Psychogenic

123
Q

What are the type 6 causes of acral lick dermatitis?

A
  1. Allergy
  2. Orthopedic
  3. Neurologic
  4. Neoplasia
  5. Focal infection
  6. Behavioral (may be involved in up to 50% of all ALDs)
124
Q

Which breeds of dogs are predisposed to behavioral acral lick dermatitis?

A

Large breeds (Doberman pinscher, Great Dane, Labrador retriever, Irish setter, golden retriever, boxer, Weimaraner, German shepherd)

125
Q

What is the median age of onset for behavioral acral lick dermatitis?

A

4 yrs

126
Q

What is the prevalence of feline psychogenic alopecia?

A

1.2 - 4.7% of itchy cats
In a study where 21 cats were referred to a behavioral service for “psychogenic alopecia”:
- 2 had just psychogenic
- 3 had both psychogenic and medical
- 16 had just medical causes

126
Q

What is feline psychogenic alopecia?

A

A form of psychogenic itch
Causes: stress-related overgrooming

127
Q

What breeds of cats are predisposed to feline psychogenic alopecia?

A

Siamese
Abyssinian *also predisposed to atopic dermatitis
Asian cats?

128
Q

What is feline idiopathic ulceration?

A

Potentially a form of psychogenic itch caused by stress
Results in a traumatic, non-healing ulcer on the dorsal neck/shoulder
One study showed all 15 cats responded to environmental modification alone

129
Q

What are the recommended treatments for neuropathic itch?

A

Barriers to reduce scratching
Local anesthetics

130
Q

What therapies have been found to be ineffective with neuropathic itch?

A

Anti-histamine
Glucocorticoids
Pain medications

131
Q

Where do TCA mediations work in the itch pathway?

A

Brain

132
Q

Where do SSRI mediations work in the itch pathway?

A

Brain

133
Q

Where does mirtazapine work in the itch pathway?

A

Brain

134
Q

Where do gabapentin/pregabalin work in the itch pathway?

A

Brain
Spinal cord

135
Q

Where do Kappa-opioid agonists work in the itch pathway?

A

Brain
Spinal cord

136
Q

Where do NK-1R inhibitors work in the itch pathway?

A

Brain
Spinal cord
Peripheral nerve fibers

137
Q

Where do topical medications work in the itch pathway?

A

Peripheral nerve fibers

138
Q

Where do antihistamines work in the itch pathway?

A

Peripheral nerve fibers

139
Q

Where does lokivetmab work in the itch pathway?

A

Peripheral nerve fibers

140
Q

What are the topical anesthetics commonly used in veterinary medicine

A

Lidocaine
Prilocaine
Pramoxine

141
Q

How do topical anesthetics work?

A

Reversibly block/close voltage gated Na+ channels
Prevent the transmission of pain impulses
Duration can vary from 30 min to more than 12 hrs

142
Q

What is the primary mechanism of action of topical capsaicin?

A

Interaction with TRPV1
Transient analgesia: desensitization of TRPV1 and functional inhibition of axonal terminals
Long-acting effect: ablation of axonal terminals

143
Q

How are calcineurin and TRPV1 related?

A

calcineurin is important for TRPV1 channel opening and synaptic efficacy

144
Q

What happened to atopic dogs which had twice daily topical application of capsaicin (0.025%) for 6 weeks?

A

Temporary worsening of pruritus in first week
Significant improvement at end by owners (but not investigators)

145
Q

What are some topical TRPM8 agonists and how do they work?

A

Menthol, icilin, cryosin-1
Excitation of Aδ fibers by TRPM8 (cold) inhibits the signaling of C fibers (itch)

146
Q

What happened to AD who had 2% cyrosin-1 applied twice daily to their skin?

A

There was no significant difference between two treatment groups

147
Q

Where do cannabinoids work in the itch pathway?

A

Peripheral nervous system and central nervous system
There are cannabinoid receptors in many locations in the skin
- keratinocytes
- nerve endings
- Langerhans cells
- fibroblasts
- sweat glands
- sebaceous glands
- hair follicles
- melanocytes

148
Q

How do cannabinoids work in regards to the neurologic sensation of itch?

A

Decreased neurotransmitter release due to
- Inhibition of Ca2+-channels
- Increasing K+ current
Some endocannabinoids like palmitoylethanolamide stabilize mast cells

149
Q

What happened to 19 experimental atopic dermatitis dogs who had a topical endocannabinoid reuptake inhibitor applied q12 to q24?

A

Significant reduction of pruritus compared to the baseline (Day 8) but no difference with placebo

150
Q

What happened to 19 cats who were fed ultramicronized palmitoylethanolamide?

A

They were better than placebo (~2x longer to relapse without methylprednisolone)

151
Q

Which opioid groups are associated with an anti-itch effect?

A

μ-opioid receptor antagonist (ex. naltrexone)
κ-opioid receptor agonist (ex. asimadoline)

152
Q

Which opioid group is associated with increased itch?

A

μ-opioid receptor agonists (ex. morphine)

153
Q

What happened when 5 atopic dogs were given the anti-NFG mAb ranevetmab?

A

anti-NGF antibody ranevetmab did not delay pruritus flares after the discontinuation of prednisolone

154
Q

Where do anti-NGF mAbs work in the itch pathway?

A

Peripherally

155
Q

What is an example of a NK-1R inhibitor?

A

Maropitant

156
Q

What does maropitant do?

A

has a similar structure to substance P so act as an antagonist and bind to the substance P receptor neurokinin 1 (NK-1R)

157
Q

What happened to 12 atopic cats given 2 mg/kg of maropitant q24h for 4 week?

A

Improved so might be effective in cats, unknown for dogs
(but was open-label and not controlled)

158
Q

How does gabapentin/pregabalin work in regards to itch and pain?

A
  • inhibits calcium channel ion entry (α2δ-1)
  • reduces glutamate levels
  • reduces hyperexcitability of neurons of the dorsal horn of the spinal cord
159
Q

What are examples of NMDA receptor antagonists?

A

Amantadine
Topiramate
Ketamine

160
Q

How do NMDA receptor antagonists work in regards to pruritus?

A

bind directly to the glutamate site of the post-synaptic NMDA receptor to inhibit the action of glutamate (which is released from the presynaptic terminal)
reduces the amount of calcium released into nerve cells
decreases the activity of these neurons and the amount of GABA released
dis-inhibit all thalamocortical pathways

161
Q

What is the difference between TCAs and SSRIs?

A

TCAs are considered “first-generation” antidepressants, and SSRIs are considered “second-generation” antidepressants
SSRIs just affect serotonin
TCAs norepinephrine and serotonin

162
Q

How do SSRIs work?

A

Increase serotonin levels in the brain by inhibiting the reuptake of serotonin into the synaptic cleft (5-HT re-uptake transporters)
- it can’t go back into the presynatic neuron
- more in the cleft so more goes into the postsynaptic neuron and brain
Probably also has other delayed effects because of delayed onset of activity

163
Q

How do TCAs work?

A

Prevent the reabsorption of serotonin and norepinephrine in presynaptic terminals (5-HT re-uptake transporters)
Also block receptors in the body, including histamine, alpha-adrenergic, and muscarinic-acetylcholine receptors

164
Q

Why do doxepin hydrochloride and amitriptyline hydrochloride have antihistamine effects?

A

They antagonize histamine H1 receptors

165
Q

What are examples of SSRIs used in veterinary medicine?

A

Fluoxetine
Paroxetine
Sertraline

166
Q

What are examples of TCAs used in veterinary medicine?

A

Amitriptyline
Clomipramine
Doxepin

167
Q

How do emollients work on the allergic itch cycle?

A

Create an occlusive barrier that moisturizes the skin
Improve skin barrier function
Decrease pruritic effect of dry skin/poor skin barrier

168
Q

What type of moisturizer is colloidal oatmeal?

A

A humectant

169
Q

What do humectants do?

A

are hygroscopic substances that form hydrogen bonds with water molecules
attracts and retains moisture in the air via absorption into the skin
can also pull water into the epidermis from the dermis

170
Q

How do humectants work on the allergic itch cycle?

A

Improve skin barrier function
Decrease pruritic effect of dry skin/poor skin barrier
*Emollients are preferred in humans

171
Q

How is lime sulfur thought to primarily work on the allergic itch cycle?

A

Dissolve pruritogenic skin surface proteins

172
Q

How do topical ceramides work in the allergic itch cycle?

A

Help to restore barrier function, thereby decreasing allergen exposure and inflammatory response

173
Q

What kind of action does histamine have on nerves in the skin?

A

Prolonged stimulation of C fibers

174
Q

How do antihistamines work?

A

Reversible competitive binding to histamine receptors (antagonist)
Some can reduce mast cell degranulation

175
Q

Why do antihistamines have a drying effect in the mouth and eyes?

A

anticholinergic properties –> decreased histamine activated exocrine secretions (salivary and lacrimal)

176
Q

Why do antihistamines have an antiemetic effect?

A

anticholinergic properties –> bund to central muscarinic receptors

177
Q

What are antihistamines contraindicated with?

A

Narrow angle glaucoma
Bladder obstruction/atony
GI obstruction/atopny
MAOIs
Pregnancy (some like hydroxyzine are teratogenic)

178
Q

What are some side effects of antihistamines?

A

Hypertension/cardiac problems
Lower respiratory tract infections (decreased secretions)
CNS sedation (increased with older generation antihistamines)
GI side effects
Dry mouth and eyes
Urinary retention
Some can lower seizure threshold
Some can have hepatotoxicity
Some are teratogenic

179
Q

Which type of antihistamine is useful for chronic idiopathic urticaria?

A

H1 and H2 blockers together

180
Q

Which antihistamine has been found to be the most effective for cats?

A

Chlorpheniramine 2 mg/kg q12h (as high as 70%)
Is a very potent H1 antagonist

181
Q

How are hydroxyzine and cetirizine related?

A

Cetirizine is the metabolite of hydroxyzine so does not require hepatic metabolism
Is bioavailable in cats, dogs, and horses

182
Q

Which commonly used antihistamines are first-generation H1 blockers?

A

Diphenhydramine hydroxychloride
Chlorpheniramine maleate
Hydroxyzine hydrochloride/pamoate
Meclizine hydrochloride
Trimeprazine (aka Temaril)
Cyproheptidine

183
Q

Which commonly used antihistamines are second-generation H1 blockers?

A

Cetirizine
Fexofenadine
Loratidine

184
Q

How does ophytrium work on the allergic itch cycle?

A

Improves skin barrier by increasing filaggrin, ceramides, and natural moisturizing factors
Decreases secretion of pro-inflammatory cytokines
Limits adhesion of Staph species so decreases pruritogenic proteases

185
Q

Where are H1 receptors expressed?

A

endothelial cells of blood vessels
vascular smooth muscle cells
neurons
keratinocytes
immune cells - dendritic cells, monocytes, neutrophils, and lymphocytes

186
Q

How do essential fatty acids work on the itch pathway?

A

Omega-3s
- reduce production of eicosanoids (prostaglandins and leukotrienes)
- decreases chemotaxis of neutrophils and monocytes
- decreased expression of leukocyte adhesion molecules
- reduce the activation of mast cells that is triggered by IgE

Omega 6s: primarily improve skin barrier

187
Q

What is the primary mechanism of glucocorticoids on the allergic itch cycle?

A

Decrease mRNA synthesis of cytokines and their receptors, phospholipase A2 and COX
- Affect nearly every part of the allergic itch cycle

188
Q

Why do glucocorticoids have such a wide range of activity?

A

Changes happen in every cell of the body since corticosteroid receptors are in every cell

189
Q

How do calcineurin inhibitors work in the allergic itch cycle?

A

blocks an calcineurin phosphatase –> prevents translocation of NFAT to the nucleus –> prevents transcription of IL-2 –> suppressed T-cell responses

also places a role in dendritic cell differentiation
reduce the size and shape of eosinophils (affects IL-5 and IL-13)

190
Q

How does oclacitinib affect allergic pruritus?

A

Preferentially inhibits function of JAK1 dependent cytokines
- IL-31 (pruritus)
- IL-2, IL-4, IL-6, IL-13 (allergy/inflammation)

JAK2 affected but 1.8 fold less
- hematopoiesis so potential suppression with higher doses
JAK 3 affected but 9.9 fold less
- involved in wider immunosuppression

191
Q

When do plasma levels of oclacitinib peak after oral administration in dogs?

A

1 hr
Half-life of 3 to 5 hrs
Ok for 24 hours dosing period

192
Q

What is the primary clearance route of oclacitinib?

A

predominant clearance route is hepatic with small amounts of renal and biliary elimination

193
Q

How does lokivetmab work?

A

binds and neutralizes canine IL-31

ACVD Exam (25 decks)

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