regulation of saliva flow Flashcards
which receptors are responsible for the regulation of saliva flow?
G-coupled receptors - GPCR
- receptors sit in cell membrane
- receive extracellular signals
- can sense chemicals
how are GPCRs activated to regulate saliva flow?
- Transmembrane helices are localised in the transmembrane
- Ligand (signalling molecule) arrive and binds to extracellular side of GPCR
- Leads to change in arrangement of the transmembrane helices
- Connecting loops (connecting the helices) are altered
- Allows binding of G proteins
- G-proteins activate second messenger systems
- Cause things to happen
how can GPCR signalling be stopped?
- Signalling is turned off when ligand and G-proteins dissociate from the receptor in the vesicles
- ligand can no longer reach the receptor
- Receptors can be recycled to cell membrane or degraded In lysosomes to permanently terminate signalling
what happens to the G-protein when a GPCR is activated?
- ligand binding induces conformational change in GCPR
- leads to G-alpha association and GDP exchange with GTP
- GTP-G-alpha changes conformation
- GTP-G-alpha dissociates from GCPR and binds to effector
- activation of effector
what does the parasympathetic pathway control in saliva regulation?
parotid gland saliva
water seerous secretion
describe the parasympathetic timulation of saliva
- acetylcholine binds to M3 muscarinic GPCR
- causes G protein dependent activation of phospholipase C
- drives conversion of phosphoinositol bis phosphate into IP3
- IP3 binds to receptors on calcium stores
- release of calcium into cellular cytosol
- increased calcium concentration
- causes activation of ANO1 chloride channel
- releases fluid through aquaporin channels or tight junctions into duct lumen
which drugs can affect serous saliva flow and how?
Cholinergic drugs
- Can induce increases in saliva flow
- Only activating cholinergic drugs can do this
Anti-cholinergic drugs
- Inhibiting M3-receptor
- Asthma
- Relax muscles in lung leading to widening of airways
- Parkinson’s disease
- Block uncontrolled movement of arms, legs and body
- Effects on oral health :
- Inactivation of receptors
- Adverse reactions or side effects
- Dry mouth syndrome
- Xerostomia
- Increase in caries formation possibly
- Anti-cholinergic drugs block to parasympathetic stimulation of saliva flow
what does the sympathetic pathway control in saliva regulation?
mucous secretions
submandibular, sublingual and minor glands
what is the stimulus and receptor in mucous secretion
sympathetic pathway
- beta-adrenergic receptor
- stimulus = noradrenaline
what is the sympathetic secondary messenger in mucous secretion?
cAMP
how are macromolecules secreted in mucous saliva?
- stimulation of noradrenaline
- binds to beta-adrenergic receptor
- activates G proteins
- activates enzyme - adenylate cyclase
- conversion of ATP to cAMP
- cAMP activates PKA
- PKA causes phosphorylation of target proteins in the cytosol
- proteins move to nucleus for mRNA synthesis
- proteins secreted by endocytosis into the lumen
what are adrenergic drugs used for?
what is their effect on saliva glands?
treat heart failure & cardiac arrest
- These drugs increase the force and rate of contraction of the heart.
- Blood pressure is also increased.
- Total peripheral resistance is also increased.
Saliva glands:
- vasoconstriction of the glands reducing salivary flow
- drug induced Xerostomia
what is the dental application of adrenergic drugs?
- vasoconstrictive actions on blood vessels.
- added to local anesthetics
- they prolong the action of the local anesthetic,
- reduce the risk for systemic toxicity
- help to create a dry field.
what are anti-adrenergic drugs
what uses do they have
Are anti-hypertensives:
- They reduce blood pressure.
Uses
- to treat hypertension, peripheral vascular disease (i.e., Raynaud syndrome) and benign prostatic hypertrophy.
what are the side effects of anti-adrenergic drugs
they can block adrenergic receptors on the mucous acini
leading to reduced protein synthesis
- Reduced quality of mucous saliva
