Stimuli Causing Salivation - GUY H CARPENTER - PDF

Stimuli that cause salivation Guy H Carpenter Salivary Research Unit, Kings College London Dental institute. In the next 45 mins... Recap salivary gland structure and secretion Define salivary reflexes Rank the importance of each reflex Handout (virtual campus) contains main points, further reading...

Stimuli that cause salivation Guy H Carpenter Salivary Research Unit, Kings College London Dental institute. In the next 45 mins... Recap salivary gland structure and secretion Define salivary reflexes Rank the importance of each reflex Handout (virtual campus) contains main points, further reading and some self-testing questions. Percentage contributions of each gland to whole mouth saliva At rest (0.2-0.5 ml/min) Stimulated (1-2 ml/min) Parotid Submandibular/ Sublingual Minor glands Parotid Submandibular/ Sublingual Minor glands 20 70 10 60 35 5 Each gland has a specific salivary protein profile 188 1) Labial saliva 2) Parotid saliva 3) Submandibular/ sublingual saliva 4) Resting whole mouth saliva 62 49 38 28 18 14 6 1 2 3 4 PGP 9.5 staining of nerves in rat submandibular gland. Catecholamine fluorescence shows sympathetic nerves Acetyl cholinesterase shows parasympathetic nerves Role of saliva in taste perception Food components need to be dissolved in saliva to reach taste buds Low salivary NaCl allows perception of NaCl Low buffer allows perception of acid Saliva has a trophic influence on taste buds Stimuli that may cause salivary secretion Masticatory Gustatory Olfactory Psychic (only occurs in animals) Movement (especially for minor glands) Thermoreceptive Possibly Nociceptive (teething?) Combinations of all the above The Masticatory-salivary Reflex Carl Ludwig in 1850 stimulated nerves to salivary glands and stimulated secretion 1854 (Colin) cannulated the horse parotid duct More recent evidence in rabbit (Hector & Linden) Record from rabbit chewing a single hard pellet on the right side Time (s) Right parotid flow (ml/min) Left parotid flow (ml/min) Output from strain gauge attached to right mandible When right flow record is inverted, shifted (to allow for latency) and superimposed onto the strain gauge record Masticatory-salivary Reflex in Man Lashley in 1916 first studied the masticatory-salivary reflex in man He recorded bilaterally from human parotid glands and showed that when chewing on one side, the ipsilateral flow was greater than the contralateral flow Lashley Cup and Cannula Bilateral recording in human Role of Intra-Oral Mechanoreceptors Output of saliva is directly proportional to masticatory forces implies Ruffini endings in the periodontal ligament. But…. Empty clenching produces no flow. And... Edentulous patients still have a masticatory reflex, which implies…. A role for gingival mechanoreceptors…. The Gustatory-salivary Reflex Stimuli delivered to gustatory receptors in Taste Buds Taste buds rapidly adapt to taste component Location of taste buds Circumvallate papilla Foliate papilla Fungiform papilla Basic tastes Basic tastes that cause salivary secretion SOUR >MSG> SALT > BITTER & SWEET However, is fat a basic taste? Linden & co. have recently given six concentrations of fat stimulation whilst recording parotid salivary flow Unable to record a salivary dose response An example of raw data from one subject salivary flow (m l/m in) Water 0.5 0 30 s 0.5 0 0.5 0 30 s 0.5 0 30 s 30 s Light cream cheese Extra-light cream cheese Original cream cheese 3.5 3.5 3 3 3 2.5 2 1.5 1 salivary flow (ml/min) 3.5 salivary flow (ml/min) salivary flow (ml/min) Full milk salivary flow (m l/m in) Semi-skimmed milk salivary flow (m l/m in) salivary flow (m l/m in) Skimmed milk 2.5 2 1.5 1 2.5 2 1.5 1 0.5 0.5 0.5 0 0 0 30 s 30 s 30 s mean salivary flow (ml/min ±S.D.) The effect of skimmed, semiskimmed and full fat milk on unilateral parotid salivary flow 0.25 0.2 skimmed 0.15 semi-skimmed 0.1 full 0.05 0 0.1% 1.7% 3.6% Combining afferents- additive 1.2 1 mls / min 0.8 0.6 0.4 0.2 0 rest chew citric acid citric+chew Olfactory salivary reflex Effect of 6 appetizing odours on submandibular salivary flow Lemon n = 10 Flow rate (ml/30 s) Flow rate (ml/30 s) Flow rate (ml/30 s) Beef n = 11 Tomato n = 11 Vanilla n = 11 Peppermint n = 12 Chocolate n = 12 Water n=8 Flow rate (% of control) Flow rate (% of control) Effect of five appetizing odours on resting parotid salivary flow Vanilla Peppermint Chocolate Open bars: Control stimulus (water) Hatched bars: Test stimulus Flow rate (% of control) n =10 Tomato Beef Parotid Submandibular Beef Beef Beef Beef Conclusions A true olfactory-parotid salivary reflex does not exist in humans However an olfactory-submandibular salivary reflex does exist in humans Psychic and conditioned Reflex Pavlov received Nobel prize (1904) for studies of reflex salivary and gastric control Used fistulas to show salivary flow from a gland in its normal environment (as opposed to anaesthetised animals). Parotid saliva, 5min stimuli P a r ot i d S a l i v a Fl ow ( S ubj e c t 1) 1.000 0.900 0.800 0.700 0.600 AM 0.500 PM 0.400 0.300 0.200 0.100 0.000 Rest Smell Taste St i mul us Chew Visual Submandibular/sublingual saliva, 5 stimuli 0.600 0.500 * * ml/min 0.400 * 0.300 n.s. * * 0.200 0.100 0.000 Rest Smell Taste Chew Visual Submandibular/ sublingual 1= Rest 2= Smell 3= Visual 4= Chew 5= Taste MG2 Statherin 1 2 3 4 5 mw Mouthwatering expt (sm/sl) 2.5 ml/min 2 1.5 1 0.5 0 Rest (1) Rest (2) Food (1) Food (2) Food (3) Taste Food exposure; Sm/sl 1 min samples 1= Rest 2= Rest 3= Food exposure 4= Food exposure 5= Taste (citric acid) 6= Taste (citric acid) 1 2 3 4 5 6 mw Psychic Stimuli Occurs in animals (even cockroaches) = set of conditions normally accompany a natural stimulus However, in man it has never been demonstrated that such stimuli cause a significant increase in flow ”mouthwatering” sensation is expulsion of pre-made saliva due to muscle activity- not a true reflex. Sleep/ diurnal Anxiety Higher centre + - Mouth feeling Smell Taste Chewing Salivary centre Parasympathetic Sympathetic + + Reflex secretion Salivary secretion Parotid secretion SM/Sl secretion Minor gland secretion Question of spit