Xerostomia_March 5

Question 1

What receptors are mainly involved in saliva secretion?

Answer 1

Parasympathetic Muscarinic 3 (M3) cholenergic receptors

• Watery secretion
• Enzyme rich
• Parotid/submandibular

Question 2

What receptors are involved in sympathetic innervation to saliva? What type of saliva is produced?

Answer 2

• Adrenoreceptor alpha-1
• Thick, viscous saliva
• Protein rich
• Mucin
• Sublingual/submandibular

Question 3

What is the resting flow rate of saliva?

Answer 3

-1mL/min (1-1.5L per day)

Question 4

How much of a role do major salivary glands play in saliva production?

Answer 4

70% submandibular
20% Parotid
10% Sublingual

Question 5

What flow rate is considered xerostomia?

Answer 5

0.14 - 0.13L per day unstimulated

Question 6

What is the composition of saliva?

Answer 6

Water (99.5%)

Solutes (0.5%)
Buffering: HCO3-; PO4 3-
Digestive: lysozyme, amylase (starch-->sugar), chloride (activates amylase)
Immune: mucins, immunoglobulin
Other ions: sodium, potassium
Other proteins/enzymes: Albumin
Urea, uric acid

Question 7

How is acetylcholine made?

Answer 7

• Choline combines with acetylcoenzyme A, catalysed by ChAT enzyme
• Stored in vesicle
• Action potential causes calcium influx and release of ACh
• Short acting as once released into synapse acetylcholinesterase breaks it down into acetate and choline
• Choline gets recycled

Question 8

What do the muscarinic receptors act on when activated?

Answer 8

M1: neuron
M2: cardiac
M3: glands

Question 9

What effects can muscarinic receptors cause?

Answer 9

Parasymp effects

Glands: activated, sweating, tears, nasal discharge
Eyes: Miosis (sphincter pupillae), near vision (ciliary muscle)
Heart: decreased rate
Blood vessels: dilate
Lung: contraction/secretion
Gut motility increased
Bladder increased urination
CNS stimulation

Question 10

What types of drugs are normally used to promote cholinergic effects? Why?

Answer 10

Acetylcholinesterase inhibitors
(As cholinergic receptors do not produce pleasant effects)

Question 11

What is the difference between therapeutic acetylcholinesterase and poisons targetting the same enzyme?

Answer 11

• Therapeutic=reversible

- Poison=irreversible

Question 12

What is the major side effect of cholinergic antagonists? What are some other side effects?

Answer 12

Dry mouth (remember that cholinergic receptors stimulate saliva flow)

• Dry eyes + blurred vision (dilated pupils)
• Constipation
• Urine retention
• Palpitations
• Drying of skin + mucosa

(For some unknown reason also vasodilation)

Question 13

What classes of drug are anti-cholinergics?

Answer 13

• Naturally occurring: atropine
• Synthetic: Quaternary amines (ipratropium, benztropine)
• Tertiary amines: antihistamine, antidepressant, antipsychotic

Question 14

What functions can cholinergic antagonists serve?

Answer 14

• Urinary incontinence (unintentional loss of urine)
• Parkinson’s (stops nerves from firing)
• Gut motility (prevents excess)
• Motion sickness (prevents nerves from firing–>this is a way for remembering, really they’re antihistamines)
• Asthma (causes bronchodilation)
• Anaesthetic
• Mydriasis (dilated pupil)
• Cycloplegia (unable to constrict lens for short range vision)
• Antidepressants
• Antipsychotics
• Antihistamine

*Note eye ones are eye drops and rarely cause dry mouth

Question 15

What non-drug therapies can be done for dry mouth?

Answer 15

• Water
• Sugar free chewing gum
• Limit caffeine/alcohol