Autacoids

Question 1

What is an autacoid?

Answer 1

A substance that acts as a local hormone

Question 2

Functions of autacoids

Answer 2

Modulate blood flow
Regulate secretions (gastric)
Alter smooth muscle function (arterioles)
Allergy, inflammation, and pain related processes

Question 3

3 classes of autacoids

Answer 3

1. Biogenic amines: histamine + serotonin
2. Polypeptides: angiotensin + bradykinin
3. Phospholipid derivatives: Prostaglandins + leukotrienes (Inflammation)

Question 4

Histamine Pools

Answer 4

1. Mast cells and basophils (circulating)
2. Non-mast cell tissues (lungs, skin, gastric mucosa)

Question 5

Histamine in mast cells

Answer 5

Stored in granules
Released by exocytotoxic extrusion (degranulation)
Act as cell signaling molecules
Involved w/ inflammation, allergy, shock
Slow synthesis

Question 6

Reasons for Histamine Release

Answer 6

Immune mediated (IgE hypersensitivities)
Drug-Induced (NMJ blockers, morphine)
Plant and animal stings
Physical injury (trauma, heat, cold)

Question 7

Other compounds released with degranulation

Answer 7

Proteases, serotonin, phospholipid derivatives (prostaglandins, leukotrienes)
AKA histamine receptor blockage will only partially antagonize the effect of degranulation (there will still be pain and inflammation)

Question 8

H1 Receptors

Answer 8

-Relaxation/contraction of vascular smooth muscle: relaxation dominates = vasodilation
- Increased capillary permeability
Fluid exudation = edema, swelling
-Bronchial smooth muscle
Generally contraction (bronchoconstriction)
-Neurotransmission
Pain and itching

Question 9

H2 receptors

Answer 9

Acts on gastric mucosa to promote secretions

Question 10

Antihistamines

Answer 10

Histamine receptor antagonists

Question 11

Do H1 antagonists prevent the release of histamine?

Answer 11

No, they are more effective in preventing the action of released histamine than reversing it.

Question 12

Diphenhydramine

Answer 12

Benadryl
1st generation H1 antagonist
Antimuscarinic, sedating

Question 13

Dimenhydrinate

Answer 13

Dramamine
1st generation H1 antagonist
antimuscarinic, sedating

Question 14

Chlorpheniramine

Answer 14

Chlor-Trimeton
1st generation H1 antagonist
less sedation

Question 15

Promethazine

Answer 15

Phenergan
Anitmuscarinic, sedating
1st generation H1 antagonist

Question 16

Loratadine

Answer 16

Claratin
2nd generation H1 antagonist

Question 17

Uses of H1 antagonists

Answer 17

1. Block endogenous histamine from participating in various allergic, anaphylactic, and other reactions.
2. Sedation, prevent motion sicknesss
3. Relax constricted bronchiolar smooth mucle
4. Inhibit histamine-dependent vasodilation and increase capillary permeability (decr. swelling and redness)
5. Antipruritic, pain relief
6. Uticaria, some dermatitis, stings, etc

Question 18

H1 antagonists adverse effects

Answer 18

CNS depression
Antimuscarinic effects (anti-SLUDGE)
CNS stimulation (paradoxical and/or w/ high dose)
Tolerance

Question 19

What is the difference between 1st and 2nd generation antihistamines

Answer 19

1st generations enter the CNS and can be sedating, 2nd generation do not.

Question 20

Famotidine

Answer 20

Pepcid
H2 antagonist
Reduce gastric acid secretion
For gastric, abomasal, and duodenal ulcers
Drug-induced gastritis, reflux

Question 21

Serotonin

Answer 21

Derived from AA tryptophan
Functions:
Regulation of gut motility
Body temp, sleep, mood, behavior, pain
Effects vary greatly between species

Question 22

Ergot Alkaloids

Answer 22

Serotonin agonists
Fescue grass toxicity in cattle
Nervousness, convulsions, peripheral gangrene from vasconstriction

Question 23

Uses of serotonin modifying drugs

Answer 23

Gastrointestinal: cisapride and metoclopramide, ondansetron
Behavioral: SSRIs (fluoxetine/prozac, sertraline/zoloft)

Question 24

Uses of SSRIs in dogs and cats

Answer 24

Dogs: seperation anxiety, compulsive behaviors, aggression
Cats: inappropriate urination, compulsive behaviors, aggression, psychogenic alopecia