Influence of circulating catecholamines on protein secretion into rat parotid saliva during parasympathetic stimulation

Multi-systemic evaluation of biological and emotional responses to the Trier Social Stress Test: A meta-analysis and systematic review

Humans experience multiple biological and emotional changes under acute stress. Adopting a multi-systemic approach, we summarized 61 studies on healthy people's endocrinological, physiological, immunological and emotional responses to the Trier Social Stress Test. We found salivary cortisol and negative mood states were the most sensitive markers to acute stress and recovery. Biomarkers such as heart rate and salivary alpha-amylase also showed sensitivity to acute stress, but the numbers of studies were small. Other endocrinological (e.g., dehydroepiandrosterone), inflammatory (C-Reactive Protein, Interleukin-6) and physiological (e.g., skin conductance level) measures received modest support as acute stress markers. Salivary cortisol showed some associations with mood measures (e.g., state anxiety) during acute stress and recovery, and heart rate showed preliminary positive relationship with calmness ratings during response to TSST, but the overall evidence was mixed. While further research is needed, these findings provide updated and comprehensive knowledge on the integrated psychobiological response profiles to TSST.

Early childhood stress responses to psychosocial stressors: The state of the science

The aim of this systematic review was to better understand whether and to what extent psychosocial stressors are associated with hypothalamic-pituitary-adrenal axis or autonomic nervous system stress responses in young children (1-6 years of age). Studies were classified by psychosocial stressors from the ecobiodevelopmental model: social and economic resources, maternal mental health, parent-child relationships, and the physical environment. Of the 2388 identified studies, 32 met full inclusion criteria, including over 9107 children. Child physiologic stress responses were measured as hair and urinary cortisol and cortisone, salivary diurnal and reactive cortisol, salivary reactive alpha-amylase, and respiratory sinus arrhythmia. There were 107 identified relations between psychosocial stressors and physiologic stress responses. Nearly two thirds of these relations suggested that children have dysregulated stress responses as either significantly blunted (n = 27) or increased (n = 37); 43 relations were not significant. Children most consistently had significantly dysregulated stress responses if they experienced postnatal maternal depression or anxiety. Some reasons for the mixed findings may be related to characteristics of the child (i.e., moderators) or stressor, how the stress response or psychosocial stressor was measured, unmeasured variables (e.g., caregiving buffering), researcher degrees of freedom, or publication bias.

The Effects of Physical Exercise on Saliva Composition: A Comprehensive Review

Saliva consists of organic and inorganic constituents. During exercise, analysis of the saliva can provide valuable information regarding training stress, adaptation and exercise performance. The objective of the present article was to review the effect of physical exercise on saliva composition. The shift in the composition of the saliva, during and after a workout, reflects the benefits of exercise, its potential risks and the capability of the saliva to serve as a health indicator. The type and the frequency of training, the physical condition and the athletes’ general health influence the hormones, immunoglobulins and saliva enzymes. The correlation between saliva and physical exercise has to be further investigated and the available knowledge to be applied for the benefit of the athletes during sports activities.

Effect of slow tempo music on markers of anxiety during cataract surgery: Randomized control trial

PURPOSE:

This study aims to objectively measure the effect of slow tempo music on various markers for anxiety.

MATERIALS AND METHODS:

This is a repeated measure randomized control trial of patients with age-related cataracts undergoing cataract extraction through phacoemulsification under local anesthesia. Patients were randomized into two groups: music group where a standardized piano music was played and control group. Salivary alpha-amylase (sAA) levels were measured at the beginning and at the end of surgery. Blood pressure and heart rate were also measured at 5 min before surgery and at four other standardized points during and after surgery. Visual Analog Scale for anxiety was also gauged: preoperatively, perioperatively, and 15 min postoperatively.

RESULTS:

Ninety-two patients were randomized equally to the music group and control group. Paired sample t-test showed a reduction in the level of sAA during surgery in the music group (P = 0.019). The odds ratio for a drop in sAA with music was 4.407 (P = 0.001). Lower systolic blood pressure was observed in the music group: at delivery of local anesthesia (P = 0.047), at first incision (P = 0.023), and during sculpting (P = 0.15). Similarly, diastolic blood pressure was lower at first incision (P = 0.019) in the music group. The visual analog scale for anxiety during surgery was found to be lower in the music group (P = 0.046).

CONCLUSION:

A slow tempo music during cataract surgery was shown to significantly reduce several indicators for anxiety at various points during cataract surgery.

Cranial osteopathic treatment and stress-related effects on autonomic nervous system measured by salivary markers: A pilot study

BACKGROUND

Variations in the concentration of salivary alpha amylase (sAA) may indicate a change in the autonomic nervous system functionality. In osteopathic medicine it has long been stated that the osteopathic manipulative treatment (OMT) can modulate the autonomic nervous system. Studies carried out on the compression of the fourth ventricle (CV4) have shown a positive effect in reducing the sympathetic tone. The goal of this pilot study is measuring the physiological response of the sAA levels after CV4 technique.

METHODS

90 subjects were randomly assigned to a sham, a control or a CV4 group. Randomization accounted for sex and score in the STAI-2 (form Y) questionnaire. Each subject completed the STAI-1 (form Y) questionnaire to evaluate the anxiety of the moment. sAA activity and saliva flow rate were measured. Saliva was collected before, immediately after and 30 min after treatment.

RESULTS

Within group analysis revealed that sAA activity increased significantly immediately after the technique application only in the CV4 group (p = 0,05). Between groups analysis show a significant difference of the sAA activity in the CV4 group respect the control group (p < 0,05), but no significant difference between CV4 and sham group (p > 0,05). The effect in the CV4 group after the intervention is highly variable and appeared to be related to the level of stress measured with the STAI-Y1 questionnaire (p = 0,002).

CONCLUSIONS

This study shows a positive effect of the CV4 procedure on sAA activity even if not significantly different from the sham procedure, probably due to the confounding effect of stress variability between groups.

A single bout of hard RPE-based cycling exercise increases salivary alpha-amylase

Exercise exerts beneficial effects on cognition, in part by stimulating an arousal response that includes the release of catecholamines. Sympathetic nervous system arousal and activation of the noradrenergic system in particular may enhance cognitive performance. Measurement of salivary alpha-amylase, a non-invasive biomarker of central noradrenergic activity, is a promising avenue for characterizing the arousal-mediated effects of exercise on cognition. However, the effectiveness of high-intensity acute exercise, and the time course of sAA concentrations following exercise, has not been clearly described. The purpose of this study was to determine the effects of 20 min of perceived exertion-based high-intensity cycling exercise on salivary alpha-amylase levels in healthy young adults. We utilized a repeated-measures design to examine the sAA response to cycling exercise, rest, and an emotional picture viewing task. Thirty-two participants between the ages of 18-30 viewed pleasant, neutral, and unpleasant pictures from the International Affective Picture System. Before and after the task, participants completed either 20 min of seated rest or cycling exercise at an intensity corresponding to 15 ("hard") on Borg's Ratings of Perceived Exertion scale. Salivary alpha-amylase was assessed at time points immediately before and after rest, exercise, and the picture viewing task. Exercise elicited a robust increase in salivary alpha-amylase approximately six times higher than that induced by emotional picture viewing. Importantly, the observed exercise-induced increase in salivary alpha-amylase returned to a level comparable to baseline after ten minutes. These findings have meaningful implications for future work characterizing the relationship between exercise and arousal-mediated effects on cognitive performance.

Colorimetric Detection of Salivary α-Amylase Using Maltose as a Noncompetitive Inhibitor for Polysaccharide Cleavage

This paper describes an approach for colorimetric detection of salivary α-amylase, one of the potential biomarkers of autonomic nervous system (ANS) activity, for enabling assessment of fatigue. The ability of α-amylase to cleave α-bonds of polysaccharides is utilized for developing a colorimetric assay. In the proposed approach, 2-chloro-4-nitrophenyl-α-d-maltotrioside as substrate releases a colored byproduct upon cleavage by salivary α-amylase. Introduction of maltose as a noncompetitive inhibitor yields desirable linear responses in the physiologically relevant concentration range (20-500 μg/mL) with a limit of detection (LOD) of 8 μg/mL (in aqueous solution). The concentrations of substrate and noncompetitive inhibitor are subsequently optimized for colorimetric detection of salivary α-amylase. A facile paper-based "strip" assay is proposed for analysis of human saliva samples with marginal interference from saliva components. The proposed assay is rapid, specific, and easy-to-implement for colorimetric detection of salivary α-amylase between 20 and 500 μg/mL. Complementary RGB (red, green, blue components) analysis offers quantitative detection with a LOD of 11 μg/mL. The two assay formats are benchmarked against the Phadebas test, a state of the art method for spectrophotometric detection of α-amylase. The reported paper-based methodology possesses a high potential for estimation of altered ANS responses toward stressors that possibly could find applications in assessment of fatigue and for monitoring onset of fatigue.

Salivary Alpha-Amylase Reactivity in Breast Cancer Survivors

The two main components of the stress system are the hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal-medullary (SAM) axes. While cortisol has been commonly used as a biomarker of HPA functioning, much less attention has been paid to the role of the SAM in this context. Studies have shown that long-term breast cancer survivors display abnormal reactive cortisol patterns, suggesting a dysregulation of their HPA axis. To fully understand the integrity of the stress response in this population, this paper explored the diurnal and acute alpha-amylase profiles of 22 breast cancer survivors and 26 women with no history of cancer. Results revealed that breast cancer survivors displayed identical but elevated patterns of alpha-amylase concentrations in both diurnal and acute profiles relative to that of healthy women, F (1, 39) = 17.95, p < 0.001 and F (1, 37) = 7.29, p = 0.010, respectively. The average area under the curve for the diurnal and reactive profiles was 631.54 ± 66.94 SEM and 1238.78 ± 111.84 SEM, respectively. This is in sharp contrast to their cortisol results, which showed normal diurnal and blunted acute patterns. The complexity of the stress system necessitates further investigation to understand the synergistic relationship of the HPA and SAM axes.

Psychosocial Stress Increases Salivary Alpha-Amylase Activity Independently from Plasma Noradrenaline Levels

Salivary alpha-amylase activity (sAA) and plasma noradrenaline (NA) concentrations are often considered to be surrogate markers of sympathetic activation in response to stress. However, despite accumulating evidence for a close association between sAA and noradrenaline and other indicators of sympathetic activity, reliability and generality of this relation remains unclear. We employed the Trier Social Stress Test (TSST) in order to directly compare the responses in sAA and NA to psychological stress in healthy volunteers (n = 23). The TSST significantly increased sAA and NA plasma levels with no significant differences in females and males. However, when subjects were divided according to their NA responses into low versus high responders, both groups did not significantly differ in their sAA before, during or after stress exposure. These data suggest that in response to acute psychological stress both plasma NA levels and sAA reflect sympathetic activity, however seemed to increase independently from each other.

Differentiating anticipatory from reactive cortisol responses to psychosocial stress

Most psychosocial stress studies assess the overall cortisol response without further identifying the temporal dynamics within hormone levels. It has been shown, however, that the amplitude of anticipatory cortisol stress levels has a unique predictive value for psychological health. So far, no "best practice" in how to investigate the anticipatory cortisol stress response has emerged. The goal of the current research was to develop a protocol that would allow for a sensitive and easy-to-implement laboratory-based investigation into anticipatory cortisol stress levels. We initially tested 26 healthy men in either an anticipation- or stress-only condition of the Trier Social Stress Test (TSST) to map the distinct timelines of anticipatory and reactive cortisol release profiles (study 1). Subsequently, we administered the TSST to 50 healthy men such that the cortisol responses to anticipatory and reactive stress components could be dissociated (study 2). In both studies we sampled saliva cortisol at high frequency (at baseline, during 10min of anticipation and during and after 10min of acute stress) and the current mood state pre- and post-stress. We found anticipatory responder rates of 20% and 40%, with peak anticipatory cortisol levels between 14 and 20min after onset of anticipation. Visible changes in reactive cortisol levels occurred only after the termination of the acute stressor. We conclude that the best practice to detect a maximum number of anticipatory responders in the TSST would be to extend the anticipation phase to 15min. In doing so, the anticipatory cortisol peak could be captured at a time-point of the actual stressor that is uninfluenced by reactive cortisol levels. Overall, we could reveal several features of anticipatory responders. Most importantly, there was a positive correlation between anticipatory and reactive stress responses. There was no association between anticipatory cortisol and alpha-amylase as well as subjective-psychological stress responses. Future studies will have to determine whether the anticipatory responders differ with respect to various stress-sensitive parameters like sex, personality, psychological wellbeing or chronic stress.

Heart rate and autonomic response to stress after experimental induction of worry versus relaxation in healthy, high-worry, and generalized anxiety disorder individuals

Generalized anxiety disorder (GAD) is the most commonly occurring anxiety disorder and has been related to cardiovascular morbidity such as cardiac ischemia, sudden cardiac death, and myocardial infarction. Both GAD and its cardinal symptom - worry - have been shown to promote muted physiological reactivity in response to laboratory and ecological stressors. Importantly, no study to date has examined the concurrent and relative contributions of trait and state worry within healthy controls, (non-clinical) high trait-worry controls, and GAD participants. The present study examined heart rate (HR), respiratory sinus arrhythmia (RSA), and salivary alpha-amylase (sAA) responses to laboratory stress during and following the experimental induction of worry versus relaxation in healthy controls (n=42), high trait worriers (n=33) and participants with GAD (n=76). All groups exhibited increased HR and decreased RSA in response to the stressor, with no differences by condition. Baseline sAA significantly moderated HR and RSA reactivity, such that higher sAA predicted greater increases in HR and decreases in RSA. There was a significant group by baseline sAA interaction such that in GAD, higher baseline sAA predicted decreased change in sAA during stress, whereas higher baseline sAA predicted greater sAA change in healthy controls. High-worry controls fell non-significantly between these groups. The present study provides additional evidence for the effect of worry on diminished HR stress response and points to possible suppression of adrenergic sympathetic stress responses in GAD.

The salivary alpha amylase over cortisol ratio as a marker to assess dysregulations of the stress systems

Different factors have been associated with changes in the regulation of the two major stress response systems of the human body, the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. Changes in these systems have been associated with various (psycho)pathologies across adulthood, and are thus frequently assessed within the context of allostatic load. Early Life Adversity (ELA) has been identified as one such factor. Individuals with histories of ELA show evidence of elevated basal and reactive salivary alpha amylase (sAA) levels (a marker of SNS activity), blunted cortisol levels (a marker of HPA axis activity), and an asymmetrical relationship between the two variables. However, variable methods used in the past to measure each variable, and the relationship between the two systems, prevent us from drawing firm conclusions. This preliminary study investigated whether the ratio of reactive sAA over reactive cortisol would be more informative to investigate the relationship between the two stress systems than the ratio of cortisol over sAA, or either marker alone, and whether there is a systematic link between this marker and subjective indexes of chronic stress and depression. We studied this in a total of 37 subjects (n=20 with signs of early life adversity and n=17 without) exposed to the Trier social stress test. Using a specific formula to determine the ratio of sAA over cortisol, we found a systematically stronger positive relationship with indexes of chronic stress and depression when compared to cortisol over sAA, or either marker alone. Our findings suggest that the ratio of sAA over cortisol might be a better marker of stress systems dysregulation than the ratio of cortisol over sAA, sAA or cortisol alone. The usefulness of this marker for other chronic stress states as found in allostatic load is discussed.

Investigation into the cross-correlation of salivary cortisol and alpha-amylase responses to psychological stress

Stress is a multidimensional construct. To accurately represent stress physiology, multiple stress measures across multiple stress-related systems should be assessed. However, associations may be masked given that different systems underlie different time courses. Salivary cortisol and alpha-amylase (sAA) are reliable biological stress markers of the sympathetic nervous system (SNS) and the hypothalamus pituitary adrenal (HPA) axis, respectively. Studies examining the link between sAA and cortisol levels in response to stress have produced inconsistent results. Here, we investigated whether the covariance of stress-induced sAA and cortisol release is dependent on the distinct temporal dynamics of the two stress markers. A total of 50 male participants were exposed to a psychological laboratory stressor with high frequency (2-min interval) saliva sampling in two independent studies. Synchronized time series of sAA and cortisol measures before, during and after stress induction were obtained. Cross-correlation analysis was applied to test for the association of sAA and cortisol levels at various stages relative to the onset of the stressor. Positive and negative cross-correlations between lagged pairs of sAA and cortisol measures were found in both studies. The strongest correlation was found for sAA preceding cortisol release by 13.5 min (r = .27, p < .001). With a smaller effect size cortisol also significantly preceded sAA by 13.5 min (r = -.16, p < .001). We suggest that sAA and cortisol stress responses are reliably associated at various time lags throughout a stressful situation. As a possible connection site between HPA axis and SNS that may underlie sAA-cortisol associations, we discuss CRF neurons of the hypothalamus involved in sympathetic regulation.

Effect of a single and repeated dose of caffeine on antigen-stimulated human natural killer cell CD69 expression after high-intensity intermittent exercise

Several studies investigating the effect of caffeine on immune function following exercise have used one large bolus dose of caffeine. However, this does not model typical caffeine consumption. Therefore, the purpose of this study was to investigate whether small repeated doses of caffeine ingested throughout the day would elicit a similar response as one large bolus dose ingested 1 h prior to exercise on antigen-stimulated NK cell CD69 expression following strenuous intermittent exercise. In a randomized cross-over design, 15 healthy males completed six 15 min blocks of intermittent running consisting of maximal sprinting interspersed with less intense running and walking. Participants had ingested either 0 (PLA), 2 mg kg(-1) body mass (BM) caffeine on three separate occasions during the day (3 × CAF) or one dose of 6 (1 × CAF) mg kg(-1) BM caffeine, 1 h before exercise. At 1-h post-exercise, the number of antigen-stimulated CD3(-)CD56(+) cells expressing CD69 was lower on 1 × CAF compared with PLA [P < 0.05; PLA: 42.0 (34.0) × 10(6) cells L(-1), 1 × CAF: 26.2 (25.0) × 10(6) cells L(-1)], with values on 1 × CAF at this time point remaining close to pre-supplement. 1 × CAF tended to attenuate the exercise-induced increase in geometric mean fluorescence intensity of CD69 expression on antigen-stimulated CD3(-)CD56(+) cells 1-h post-exercise [P = 0.055; PLA: 141 (28)%, 1 × CAF: 119 (20)%]. These findings suggest that although one large bolus dose of caffeine attenuated the exercise-induced increase in antigen-stimulated NK cell CD69 expression 1 h following strenuous intermittent exercise, this attenuation at no point fell below pre-supplement values and caffeine does not appear to depress NK cell CD69 expression.

Salivary alpha-amylase as a non-invasive biomarker for the sympathetic nervous system: current state of research

Development of new biomarkers is a constantly evolving field of research endeavor in psychoneuroendocrinology. Salivary biomarkers have received special attention since they are readily accessible and easily obtained. Salivary alpha-amylase (sAA) has been proposed as a sensitive biomarker for stress-related changes in the body that reflect the activity of the sympathetic nervous system (SNS), and a growing body of research is accumulating to support the validity and reliability of this parameter. However, questions remain to be answered before sAA can be accepted as an index of SNS activity. This review describes sAA as an emerging biomarker for stress and provides an overview of the current literature on stress-related alterations in sAA. It critically discusses how sAA might reflect changes in the autonomic nervous system. Finally, current and future fields for the application of sAA measurement are outlined.

Salivary Genomics, Transcriptomics and Proteomics: The Emerging Concept of the Oral Ecosystem and their Use in the Early Diagnosis of Cancer and other Diseases

There is an increasingly growing interest world-wide for the genomics, transcriptomics and proteomics of saliva and the oral cavity, since they provide a non-invasive source of unprecedently rich genetic information. The complexity of oral systems biology goes much beyond the human genome, transcriptome and proteome revealed by oral mucosal cells, gingival crevicular fluid, and saliva, and includes the complexity of the oral microbiota, the symbiotic assembly of bacterial, fungal and other microbial flora in the oral cavity. In our review we summarize the recent information on oral genomics, transcriptomics and proteomics, of both human and microbial origin. We also give an introduction and practical advice on sample collection, handling and storage for analysis. Finally, we show the usefulness of salivary and oral genomics in early diagnosis of cancer, as well as in uncovering other systemic diseases, infections and oral disorders. We close the review by highlighting a number of possible exploratory pathways in this emerging, hot research field.

The psychosocial stress-induced increase in salivary alpha-amylase is independent of saliva flow rate

The stress response of salivary alpha-amylase (sAA) has been suggested as an index for sympathetic nervous system activation. However, concurrent inhibition of the parasympathetic nervous system is discussed as a confounder due to suppression of saliva flow rate. Here we set out to test the influence of stress-induced changes in flow rate on sAA secretion. Twenty-six subjects underwent the Trier Social Stress Test and a control condition. Saliva was sampled by passive drooling or salivettes. Saliva flow rate, sAA levels and output, salivary cortisol, and heart rate variability were measured. Flow rate increased only when sampled by passive drooling. Stress-induced increases in amylase levels were correlated with increases of amylase output but not with flow rate. Results indicate that flow rate is not a confounder of stress-induced sAA activation and suggest that valid measurements of sAA can be obtained by salivettes without the need for assessment of flow rate.

Salivary IgA Responses to Prolonged Intensive Exercise following Caffeine Ingestion

PURPOSE

Prolonged, intensive exercise is associated with a reduction in concentration and secretion of salivary IgA (s-IgA). Saliva composition and secretion are under autonomic nervous system control, and caffeine ingestion, a widespread practice among athletes for its ergogenic properties, is associated with increased sympathetic nervous system activation. Therefore, this study investigated the influence of caffeine ingestion on s-IgA responses to prolonged, intensive exercise.

METHODS

In a randomized crossover design, 11 endurance-trained males cycled for 90 min at 70% VO2peak on two occasions, having ingested 6 mg x kg(-1) body mass of caffeine (CAF) or placebo (PLA) 1 h before exercise. Whole, unstimulated saliva samples were collected before treatment (baseline), preexercise, after 45 min of exercise (midexercise), immediately postexercise, and 1 h postexercise. Venous blood samples were collected from a subset of six of these subjects at baseline, preexercise, postexercise, and 1 h postexercise.

RESULTS

An initial pilot study found that caffeine ingestion had no effect on s-IgA concentration, secretion rate, or saliva flow rate at rest. Serum caffeine concentration was higher on CAF than PLA at preexercise, postexercise, and 1 h postexercise (P < 0.001). Plasma epinephrine concentration was higher on CAF than PLA at pre- and postexercise (P < 0.05). s-IgA concentration was higher on CAF than PLA at mid- and postexercise (P < 0.01), and s-IgA secretion rate was higher on CAF than PLA at midexercise only (P < 0.02). Caffeine ingestion did not affect saliva flow rate. Saliva alpha-amylase activity and secretion rate were higher on CAF than PLA (main effect for trial, P < 0.05).

CONCLUSIONS

These findings suggest that caffeine ingestion before intensive exercise is associated with elevated s-IgA responses during exercise, which may be related to increases in sympathetic activation.

Acinar degranulation in the rat parotid gland induced by neuropeptides

Vasoactive intestinal peptide (VIP, 4 microg kg(-1) min(-1)), substance P (3 microg kg(-1) min(-1)) and neurokinin A (2.5 microg kg(-1) min(-1)) were infused intravenously for 30 min in anaesthetized rats and the effects of these peptides on the parotid gland were examined. VIP reduced the numerical density of parotid acinar secretory granules, storing proteins, by 29 % and the glandular amylase activity by 33 %. Substance P reduced the number of secretory granules by 18 % but the amylase activity was unchanged. These results make VIP and substance P likely contributors to the parasympathetic non-adrenergic, non-cholinergic (NANC)-evoked parotid acinar degranulation. Neurokinin A, on the other hand, caused no reduction in granular number but reduced the glandular amylase activity by 19 %, indicating vesicular protein secretion.

Ascorbate deficiency impairs the muscarinic-cholinergic and ss-adrenergic receptor signaling systems in the guinea pig submandibular salivary gland

Ascorbic acid is preferentially concentrated in the hypothalamus, pituitary and adrenal glands. Its level in the acini of salivary glands is relatively high. We therefore hypothesized that ascorbate may have a role in salivary gland function. Ascorbate-deficient guinea pigs had lower stimulated whole salivary flow rates than well-fed, age-matched controls (P: < 0.005). Total salivary protein concentration was also markedly (P: < 0.005) reduced in the deficient guinea pigs. SDS-PAGE and densitometric quantification of protein bands confirmed significant reduction in specific salivary proteins (e.g., amylase, proline-rich proteins) in the saliva samples of malnourished guinea pigs. Some protein bands not seen in control saliva were detected in the saliva of malnourished guinea pigs. Ascorbate deficiency also produced a significant (P: < 0.005) reduction in the ss-adrenergic receptor density (subtype 1; 95 +/- 19 fmol/mg protein compared with 179 +/- 27 fmol/mg protein for the controls). No significant difference was observed between the two groups with respect to the ss-adrenergic receptor subtype 2. Additionally, ascorbate-deficient guinea pigs had significantly lower muscarinic-cholinergic receptor densities (50 +/- 5 vs. 74 +/- 8 fmol/mg protein for controls). Our data support the conclusion that diminished membrane receptors might impair the capacity of the transmembrane signaling system, resulting in salivary gland hypofunction in ascorbate-deficient guinea pigs. Without implying extrapolation of our findings in experimental animals to humans, it is perhaps relevant that many conditions often associated with salivary gland hypofunction in humans (e.g., smoking or drug ingestion) deplete cellular ascorbate.

Carbohydrate and fluid intake affect the saliva flow rate and IgA response to cycling

PURPOSE

The purpose of this study was to examine the effect of regular CHO beverage ingestion and restricted fluid intake on various salivary parameters during prolonged cycle exercise.

METHODS

In a randomized block design, 15 recreationally active men cycled for 2 h at 60% VO2max on three occasions, separated by 1 wk. On the CHO and placebo (PLA) treatments, subjects consumed either a glucose (60 g x L(-1)) or placebo drink before (400 mL), during (150 mL every 15 min), and after (400 mL) the exercise. On the restricted fluid intake (RFI) treatment subjects were given a total of 200 mL of placebo fluid to take as desired every 15-min during the exercise. Timed, unstimulated saliva samples were collected preexercise, at 1, 1.5, and 2 h of exercise and at 1 h postexercise. Blood samples were obtained from a subset of 8 subjects preexercise, postexercise, and at 1 h postexercise.

RESULTS

Postexercise plasma glucose levels were 18% and 20% lower on the PLA and RFI treatments, respectively, compared with the CHO treatment (P < 0.01). Saliva flow rates were significantly higher on the CHO treatment compared with the RFI treatment at 1.5 h and 2 h of exercise (P < 0.01 and P < 0.05, respectively). Salivary IgA (s-IgA) concentration was significantly lower on the CHO treatment compared with the RFI treatment throughout the exercise (P < 0.05). No other differences were seen between treatments for either saliva flow rate or s-IgA concentration. Neither s-IgA secretion rate, alpha-amylase activity, nor alpha-amylase secretion rate were affected by treatment.

CONCLUSIONS

These findings suggest that CHO and fluid intake influence the s-IgA and saliva flow rate response to prolonged submaximal exercise.

High-resolution electrophoretic analysis of rat parotid salivary proteins

Silver staining and high-resolution electrophoretic methods have been used to compare the protein composition of rat parotid saliva evoked in response to (i) parasympathetic stimulation (including the nonadrenergic, noncholinergic, atropine-associated secretion), (ii) sympathetic stimulation, or (iii) the infusion of neuropeptides with secretagogue activity (substance P, calcitonin gene-related peptide, neuropeptide Y, or vasoactive intestinal peptide). The different stimuli influenced the protein concentration and flow rate of the evoked secretion but had little effect upon the protein composition of the saliva. In contrast to earlier studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Coomassie blue staining, the combination of silver staining and two-dimensional electrophoresis (2-DE) revealed many newly detected proteins. The results indicate that the protein composition of rat parotid saliva is more complex than previously reported but is unaffected by the mode of stimulation.

Sympathetic mediation of salivation induced by intracerebroventricular pilocarpine in rats

Central cholinergic activation by pilocarpine induces salivation dependent on the integrity of forebrain areas. The present work investigates the autonomic mediation of this salivation. Pilocarpine (500 nmol/rat) was injected into the lateral ventricle (LV) of tribromoethanol-anesthetized adult male rats. Preweighed cotton balls were inserted into the oral cavity and weighed again 7 min later. Alpha-adrenoceptor antagonists (3-50 micromol/kg) prazosin (alpha1), yohimbine (alpha2) or propranolol (beta) injected intraperitoneally (i.p.) produced, 80%, 20% and 0% inhibition respectively of the LV pilocarpine-induced salivation. Intracerebroventricular injections (160 nmol) of the antagonists did not alter the effects of pilocarpine injected into the LV. Bilateral section of chorda tympani nerve or bilateral sympathetic cervical ganglionectomy produced 0% and 40% inhibition of pilocarpine-induced salivation, respectively. Ganglionectomy did not alter salivation induced by i.p. injection of pilocarpine (4 micromol/kg). The results indicate that there is a large sympathetic contribution to the salivation induced by central cholinergic activation.

Saliva composition and exercise

Little attention has been directed toward identifying the changes which occur in salivary composition in response to exercise. To address this, our article first refers to the main aspects of salivary gland physiology. A knowledge of the neural control of salivary secretion is especially important for the understanding of the effects of exertion on salivary secretion. Both salivary output and composition depend on the activity of the autonomic nervous system and any modification of this activity can be observed indirectly by alternations in the salivary excretion. The effects of physical activity (with reference to factors such as exercise intensity and duration, or type of exercise protocol) on salivary composition are then considered. Exercise might indeed induce changes in several salivary components such as immunoglobulins, hormones, lactate, proteins and electrolytes. Saliva composition might therefore be used as an alternative noninvasive indicator of the response of the different body tissues and systems to physical exertion. In this respect, the response of salivary amylase and salivary electrolytes to incremental levels of exercise is of particular interest. Beyond a certain intensity of exercise, and coinciding with the accumulation of blood lactate (anaerobic threshold or AT), a 'saliva threshold' (Tsa) does indeed exist. Tsa is the point during exercise at which the levels of salivary alpha-amylase and electrolytes (especially Na+) also begin to rise above baseline levels. The occurrence of the 2 thresholds (AT and Tsa) might, in turn, be attributable to the same underlying mechanism, that of increased adrenal sympathetic activity at high exercise intensities.

Intracellular transport and secretion of salivary proteins

Intracellular transport and secretion of salivary proteins are major activities of salivary acinar cells. While the major intracellular pathway followed by salivary proteins following their synthesis has been described previously, there is only limited understanding of how this process is regulated at the molecular level. Studies of salivary proteins, especially proline-rich proteins, expressed in an endocrine cell line have begun to provide insight regarding intermolecular interactions during transport and the role played by structural signals during intracellular sorting. Analysis of the secretion of newly synthesized salivary proteins in parotid tissue has shown that there are multiple pathways of discharge from acinar cells. While granule exocytosis is the major pathway, at least two other pathways that export salivary proteins have been found to originate from maturing secretion granules. These pathways may contribute to other acinar cell functions, including secretion of proteins in the absence of acute stimulation and support of the secretory process for fluid and electrolytes.

Two regulated secretory pathways for newly synthesized parotid salivary proteins are distinguished by doses of secretagogues

Low doses of the muscarinic agonist pilocarpine (0.1-1 microM) and the beta-adrenergic agonist isoproterenol (0.5-4 nM) stimulate a minor regulated secretory pathway for salivary proteins in rat parotid lobules. Newly synthesized proteins (labeled biosynthetically) are selectively discharged, and they are secreted in the same relative proportions as observed in constitutive-like unstimulated secretion but different from the proportions of older proteins that are discharged by granule exocytosis in response to higher doses of secretagogue. The response to low doses of agonists is transient and involves output of no more than 1–2% of tissue-associated amylase. The same increase in output of pulse-labeled proteins is observed when agonist is added at various chase times (1.5-6 hours), implying that release occurs from a post-Golgi storage pool. Stimulation for 40 minutes significantly depletes the storage pool as a second stimulation elicits smaller output. Stimulation also partially depletes labeled proteins from subsequent constitutive-like secretion after the agonist is removed implying that the constitutive-like and low dose agonist mediated pathways draw on the same pool of secretory proteins. While these results indicate that acinar cells have a second regulated secretory pathway, this new pathway is unlikely to contribute uniquely to the protein composition of parotid secretion. Rather it may serve a different role in secretion at the apical cell surface.

Anaerobic threshold in children: determination from saliva analysis in field tests

The purpose of this study was to determine the anaerobic threshold of children by the analysis of saliva collected during field tests. A group of 25 children (mean age, 10.5 years) performed an incremental exercise test on a track, consisting of 4-min stages at increasing running velocities. Before each test (at rest) and at the end of each stage, both blood (via finger pricks) and saliva samples (for measurement of salivary concentrations of Na+ and Cl-) were collected to determine lactate threshold (Thla-) and saliva threshold (Thsa), respectively. There were no significant differences between values of Thla- and Thsa when expressed either as running velocity [mean Thla-, 10.73 (SD 1.96) km.h-1; mean Thsa, 10.89 (SD 1.69) km.h-1)] or heart rate [Thla-, 182(SD 14) beats. min-1 Thsa 183 (SD 11) beats.min-1]. In addition, correlations between Thsa and Thla were high, when both values were expressed as running velocity in kilometres per hour (r = 0.89; P < 0.001), or heart rate in beats per minute (r = 0.90; p < 0.001). In conclusion, these findings suggested that saliva analysis would be a valid method for anaerobic threshold determination in field tests.

Saliva electrolytes as a useful tool for anaerobic threshold determination

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 min, until capillary blood lactate exceeded 4 mmol.l-1. A maximal test for maximum O2 uptake (VO2max) determination (initial load of 100 W and load increases of 50 W per 2 min) was also performed. Saliva and blood samples were obtained only in the submaximal test. Saliva threshold (Thsa) was defined as the point at which the first increase in either Cl- or Na+ occurred. Catecholamine threshold (Thca) was defined as the point at which a nonlinear increase occurred in either adrenaline or noradrenaline. The lactate (Thla) and ventilatory (Thve) thresholds were determined according to published criteria. No significant differences were found between Thsa values and the other methods of threshold determination. A high correlation was found between Thsa and Thla (r = 0.82, P < 0.01), and Thsa and Thca (r = 0.75, P < 0.05). These results support the validity of Thsa as a new method for noninvasive determination of the anaerobic threshold.

Protein synthesis in the major salivary glands of the rat and the effects of re-feeding and acute ethanol injection

Rates of protein synthesis in the major salivary glands of the rat were accurately determined in vivo using the 'flooding dose' technique and the effects of reflex stimulation through feeding or acute ethanol treatment were assessed. Rats were divided into three groups. The control group was fasted overnight, the re-fed group was also fasted then re-fed the following morning and the third group received an intraperitoneal injection of ethanol after an overnight fast. In control rats the sublingual gland had a higher rate of protein synthesis than the other glands. After a feed the rate of protein synthesis in parotid glands was approximately double that of controls whilst that of the submandibular glands had increased by 24% and the sublingual glands remained unchanged. Acute ethanol injection led to a reduced rate of protein synthesis in all glands. The higher rate of protein synthesis in sublingual glands under fasting conditions may be related to the spontaneous secretion of fluid and protein from this gland, which would require a constant replenishment of secretory protein by synthesis. Protein synthesis in the parotid gland, like secretion, appears to be closely linked with the reflex stimulation caused by mastication. The smaller increase in rate of protein synthesis seen in the submandibular gland after a re-feed does not appear to have been recorded before. It could be mediated by the increased reflex stimuli caused by mastication or by some circulating factor. The mechanism by which ethanol reduces protein synthesis in all glands is uncertain.

The effect of adrenergic agonists and antagonists on cysteine-proteinase inhibitor (cystatin) in rat saliva

The effect of a number of adrenergic agonists and antagonists on the induction of rat salivary cystatin was investigated. A highly sensitive and specific radioimmunoassay was used to determine cystatin in rat whole saliva. Treatment for 10 consecutive days with a non-specific beta-adrenergic agonist isoproterenol, or the beta 1-adrenergic agonists dobutamine or methoxyphenamine, resulted in the induction of the salivary cystatin. Induction was also found in rats treated for 10 days with arterenol. Only trace quantities of cystatin could be detected in saliva of rats treated with the beta 2-adrenergic agonists terbutaline or salbutamol. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, proctocol or atenolol the production of cystatin was totally suppressed. However, the beta 2-antagonist, ICI 118551, produced only a partial reduction in salivary cystatin induction elicited by isoproterenol. The findings suggest that the induction of salivary cystatin is regulated, in part, by beta 1-adrenergic receptor stimulation.

Separation of the proteins of rat parotid saliva by hydrophobic-interaction chromatography

Parasympathetically-evoked rat parotid salivary proteins were resolved into 11 peaks by hydrophobic-interaction chromatography. SDS-PAGE indicated that most peaks contained a single major component and that only one major protein was not chromatographed. The findings indicate that hydrophobic-interaction chromatography can be used in the quantification of changes in individual salivary proteins under different experimental conditions, and in the purification of individual salivary proteins.

Saliva flow and composition in humans exposed to acute altitude hypoxia

The effects of acute hypoxia (2 days at 4350 m) on whole saliva flow and composition were studied on 12 sea-level natives, at rest and following a maximal exercise. Exercise, performed in normoxia and hypoxia, did not induce variations in saliva flow rate, saliva potassium or alpha-amylase concentrations. In contrast, acute hypoxia did lead to an increase in mean saliva flow rate both at rest (0.63 ml.min-1 to 0.93 ml.min-1, P less than 0.01) and after exercise (0.56 ml.min-1 to 1.06 ml.min-1, P less than 0.05) and a decrease in mean saliva potassium concentration at rest (20.8 mmol.l-1 to 14.7 mmol.l-1, P less than 0.01) as well as after exercise (21.7 mmol.l-1 to 16.5 mmol.l-1, P less than 0.05). This effect might be the consequence of a hypoxia-induced stimulation of the parasympathetic nervous system.

Effects of parasympathectomy on protein composition of sympathetically evoked parotid saliva in rats

1. Male Wistar rats were given unilateral postganglionic parasympathectomies by sectioning the auriculo-temporal nerve. 2. Analyses of the protein compositions of sympathetically induced saliva from both glands 1 week later revealed changes in the proportions of different secretory proteins, in particular amylase and basic proline-rich proteins were decreased. 3. These results suggest that parasympathetic impulses are required for the normal synthesis of amylase by parotid parenchyma in rats. Basic proline-rich proteins, known to require a sympathetic drive for normal synthesis, appear to require a parasympathetic input as well.

Gustatory-salivary reflex: neural activity of sympathetic and parasympathetic fibers innervating the submandibular gland of the hamster

Electrophysiological experiments were performed to clarify the neural control mechanisms subserving gustatory-salivary reflex in anesthetized and decerebrate hamsters. Efferent neural activities of postganglionic sympathetic and preganglionic parasympathetic fibers, innervating the submandibular gland, were recorded when taste stimuli were infused into the oral cavity. Neural activities of primary gustatory afferents were also recorded from the chorda tympani (innervating the anterior part of the tongue) and the glossopharyngeal nerve (innervating the posterior part of the tongue). The parasympathetic fibers showed a low rate of spontaneous discharges (about 0.3 Hz), and responded tonically in an excitatory manner to taste stimulation. The magnitude of parasympathetic activity was highly correlated with the magnitude of gustatory afferent responses of the chorda tympani rather than that of the glossopharyngeal nerve. On the other hand, the sympathetic fibers showed irregular burst discharges (1.5 burst/s), and the rate of burst discharges was increased in response to high concentrations of HCl (0.03 M) or NaCl (1 M) solutions. Deafferentation experiments suggest that the parasympathetic activity is mainly influenced by gustatory information via the chorda tympani, while the sympathetic activity can be evoked by both the chorda tympani and glossopharyngeal nerve.

Differences in the protein composition of rat parotid salivas evoked by sympathetic and parasympathetic nerve stimulation

1. Parotid salivas were collected from rats following electrical stimulation of either the sympathetic or parasympathetic nervous supplies. 2. The protein compositions of these salivas were compared using high performance ion-exchange chromatography (FPLC), SDS electrophoresis and biochemical assay. 3. Chromatography and electrophoresis indicated differences between the protein compositions of sympathetic and parasympathetic salivas. 4. Protein secretion derived solely from the exocytosis of parotid acinar cells cannot account for these differences.

Protein secretion from the cat parotid gland on nerve stimulation

1. The output and composition of proteins in nerve stimulated saliva samples were compared. 2. Protein output upon parasympathetic stimulation was higher than following sympathetic stimulation and was accompanied by an obvious degranulation of acini with the former but not the latter. These events are the converse of those in the rat parotid gland. 3. Superimposition of sympathetic upon parasympathetic stimulation caused an augmented output of salivary protein. 4. Electrophoresis of salivas revealed differences between individual cats in protein composition but not between differently stimulated salivas.

Dopamine actions in vitro on enzyme and electrolyte secretion from normal and sympathectomized rat parotid glands

1. Adult rats were denervated unilaterally by removal of the left superior cervical ganglion or chemically denervated with 6-hydroxydopamine or reserpine. Two weeks later the parotid glands were used for in vitro secretory studies and their catecholamines and major metabolites were measured. 2. Noradrenaline concentrations were reduced 2 weeks after surgical sympathectomy and reserpine pre-treatment 18 h previously, whereas 6-hydroxydopamine pre-treatment for 3 days reduced both noradrenaline and dopamine concentrations. 3. Dopamine caused a prominent amylase release from incubated control glands. However, a subsensitivity for dopamine-induced amylase release was recorded on the denervated side. 4. Dopamine caused a prominent potassium efflux measured as 86Rb+ efflux from control glands, but was without effect in denervated glands. This is in contrast to noradrenaline-induced 86Rb+ efflux which was equally effective in both denervated and control glands. 5. Dopamine caused [3H]noradrenaline efflux in control glands, but was without effect in surgically denervated glands and in glands pre-treated with reserpine or 6-hydroxydopamine. 6. It is concluded that dopamine-induced potassium release is caused by a presynaptic action on noradrenergic nerves, whereas dopamine-induced amylase release has a presynaptic and a postsynaptic component. The results suggest a specific action of dopamine in salivary glands, with different effects on enzyme release and ionic fluxes.

The effects of atropine and chronic sympathectomy on maximal parasympathetic stimulation of parotid saliva in rats

1. The effects of stimulating the postganglionic parasympathetic nerve to the parotid gland, the auriculo-temporal nerve, continuously at 40 Hz for 80 min have been assessed on the flow of saliva and its amylase content during each 10 min period and on the glandular morphology at the end of the stimulation, in female Sprague-Dawley rats under chloralose anaesthesia. Adrenergic responses were blocked by prior administration of dihydroergotamine (1 mg/kg I.P.) and propranolol (1 mg/kg I.P.). The contralateral unstimulated parotid gland from each animal was used for morphological control purposes. 2. In normal animals there was a copious flow of saliva reaching 3 ml or more in 80 min. It was well maintained after a gradual small decline and the flow in the last 10 min period was still 60% of that in the initial period. Amylase output was relatively high in the initial period but then declined more rapidly than the flow. The acini were densely packed with granules on the control side and showed a moderate amount of degranulation on the parasympathetically stimulated side. 3. After atropine (2 mg/kg I.V.), normal animals initially showed a moderate flow of saliva, being 41% of the non-atropinized animals, but there was a rapid decline and the total flow over 80 min was only 15% of that in the non-atropinized animals. The amylase secreted was also high initially and showed a rapid decline; the total amount secreted was similar to that in non-atropinized animals. The morphology was similar to that in non-atropinized animals and showed a similar loss of acinar granules on the stimulated side. 4. Chronic bilateral postganglionic sympathectomy (4-6 weeks duration) caused a drastic reduction in the capacity of the gland to secrete saliva in response to parasympathetic stimulation, reaching only one-third of that from normal animals. The initial output of amylase was greater than in normal animals but the total output was similar. The control unstimulated sympathectomized glands appeared similar morphologically to normal resting glands. However, on the parasympathetically stimulated side, besides the usual amount of acinar degranulation, there was also a conspicuous development of acinar vacuolation, not seen in the other groups of animals.(ABSTRACT TRUNCATED AT 400 WORDS)

The influence of plasma catecholamines on methotrexate-enhanced rat salivary gland protein secretion

The acetylcholine-elicited secretory output of parotid protein and amylase, and of submandibular protein from rats receiving 15 mg methotrexate (MTX)/kg for 3 days were 3-6 times greater than that from control animals. Plasma epinephrine and norepinephrine levels in MTX-treated animals were 4-14 times greater than control values. Adrenalectomy reduced the plasma-catecholamine levels, and the acetylcholine-stimulated salivary protein and amylase output. Thus MTX-enhanced salivary protein secretion evoked by acetylcholine stimulation may be mediated, at least in part, by elevated levels of circulating catecholamines.

Nerve interactions in salivary glands

In the salivary reflex, not only secretory cells are activated, but also myo-epithelial cells are contracted to support these cells and promote the flow of saliva, and blood vessels dilate to meet the increased demands of the tissues. The various effector cells often receive nerves from both parts of the autonomic system, and interactions may occur when the nerves act on the same type of effector, or on different types of effectors. While in an experiment electrical stimulation of the sympathetic trunk may decrease a parasympathetic salivary flow by causing marked vasoconstriction, this does not occur in the salivary reflex, since the vasoconstrictors do not take part. On the contrary, the normal sympathetic vasoconstrictor tone of the resting gland is easily overcome by activity in parasympathetic vasodilator nerves when secretion starts. Pronounced synergism can be demonstrated between sympathetic and parasympathetic secretory nerves. In dogs, for instance, in which sympathetic secretion is beta-adrenoceptor-mediated, this is marked in the case of fluid secretion. In rats and rabbits, in which beta-receptors elicit secretion of amylase, the potentiating interaction among the nerves is striking when amylase secretion is considered. Even the random release of acetylcholine from the post-ganglionic parasympathetic axons, by itself insufficient to evoke secretion, can increase the sympathetic effects. Motor nerves interact with secretory nerves by causing myo-epithelial contraction, mechanically promoting secretion. Interactions between the nerves in their long-term regulatory function on the sensitivity of the acinar secretory and myo-epithelial cells can also be demonstrated.

The proper role of nerves in salivary secretion: a review

Consideration of the history of this subject has created a perspective which helps one to appreciate how errors in thinking have occurred and why some have persisted, despite subsequent improvements in information. The most enduring misconception has been that the drying of the mouth under stress is due to sympathetic inhibitory fibers, a view that must be eradicated, for such fibers do not exist. The inhibition is due to central influences from higher centers acting on the salivary centers and thereby suppressing reflex activity. Wide variations exist in the neuro-effector arrangements and in the cellular responses in different glands from different species. Myoepithelial cells are usually contracted by both parasympathetic and sympathetic nerves. The blood vessels also receive a dual innervation, but parasympathetic impulses cause vasodilatation as part of secretion, whereas the sympathetic vasoconstrictor fibers are part of a more generalized vascular control system and not a direct part of the reflex secretory sympathetic pathway. Parasympathetic drive usually provides the main stimulus for fluid formation by parenchymal cells, whereas sympathetic nerves tend to increase the output of pre-formed components from certain cells. Absence of nerve impulses causes variable atrophic and other metabolic effects on the parenchymal cells. Evidence is beginning to accrue that certain nerve impulses may influence resynthetic activities. Vacuolation, often found experimentally after strong stimulation, also occurs to a variable extent in certain cells as a normal part of reflex secretion and may therefore have an effect on the components entering the saliva. If rupture of vacuoles occurs, then this may contribute to the salivary amylase that is present in the blood. Recent evidence points to the possibility that, even in a monomorphic gland, not all of the components necessarily enter nerve-induced saliva in "parallel" proportions. Consideration of current information has enabled some provisional generalizations about the roles of the secretory nerves to be suggested in the summary, but they must not be considered immutable.

Electron microscopy of watery vacuole formation in rat parotid acinar cells during reflex stimulation

Reflex stimulation from eating hard chow caused variable degrees of watery vacuolation, most conspicuously in animals that had eaten the most food; this was accentuated by eating in the cold. Some vacuolation occurred in the absence of sympathetic impulses but there was much more in glands receiving both parasympathetic and sympathetic impulses. Vacuole formation was often associated with, but not dependent upon, a degree of acinar degranulation. The vacuoles appeared to originate either from the inner side of the Golgi apparatus, near condensing vacuoles, or from ballooning within the rough endoplasmic reticulum; some vacuoles appeared to arise close to secretory granules. Certain cellular components, including secretory granules, entered the contents of vacuoles, which also often had connections with lumina. Many basally-located vacuoles were large and bounded only by a tenuous layer of cytoplasm which was contained by the basal lamina. Vacuole formation may be related to strong stimulation of susceptible cells, which occurs to a variable extent during natural reflex secretion, as well as during artificial stimulation. Thus, under normal conditions, certain macromolecular components might enter saliva via this route and not solely by exocytosis. Leakages from acinar vacuoles could also occur into the glandular interstices, accounting for some of the parotid amylase found in peripheral blood.

Vasoactive intestinal polypeptide and acetylcholine stimulate exocrine secretion of epidermal growth factor from the rat submandibular gland

The effect of vasoactive intestinal polypeptide (VIP) and acetylcholine on secretion of epidermal growth factor (EGF) from the rat salivary glands was investigated. VIP in doses of 3 X 10(-10) to 3 X 10(-8) mol/kg per h stimulated secretion of saliva and total output of EGF dose-dependently. Acetylcholine also stimulated salivation and output of EGF. VIP in a dose of 3 X 10(-11) to 3 X 10(-10) mol/kg per h enhanced the stimulatory effect of acetylcholine, but this effect disappeared when the dose of VIP was increased. Adrenalectomy decreased acetylcholine stimulated total output of EGF by approximately 50%, but only by 20% when acetylcholine plus VIP was administered. EGF was localized to the convoluted granular tubules in the submandibular gland, whereas EGF could not be detected in the remaining salivary glands. The results suggest that VIP and acetylcholine cooperate in the control of exocrine secretion from the rat salivary glands. The effect of acetylcholine, however, seems to be partly dependent on circulating catecholamines.

Sympathetic stimulation of amylase secretion during a parasympathetic background activity in the rat parotid gland

The amylase secretion in vivo was examined in the rat parotid gland. A comparison was made between individual stimulation of sympathetic and parasympathetic nerves and simultaneous activation of both nerves. When sympathetic stimulation was superimposed on a parasympathetic background activity, amylase secretion was elicited at a frequency far below the threshold for secretion of fluid, and increased in a frequency-dependent way. This augmented amylase secretion, seen when the two nerves were activated at the same time, gave an amylase output which far exceeded the sum obtained at individual nerve stimulation. The sympathetic amylase secretion obtained in a background of parasympathetic activity seemed to be dependent entirely on beta 1-adrenoceptors. When high sympathetic stimulation frequency (3-10 Hz) was used a reduction in salivary flow was seen, which was accompanied by a reduced amylase output. This effect was counteracted by alpha-adrenoceptor blockade. Isoprenaline, injected intravenously during an ongoing parasympathetic activity, was found to evoke an augmented amylase secretion in a similar way as sympathetic nerve stimulation.

Amylase in parotid saliva of rats after sympathetic nervous decentralization

The marked increase in the amylase secretion that occurs in parasympathetic saliva some days after sympathetic ganglionectomy occurred after decentralization also; hence, it results from lack of impulses from the central nervous system. It occurred whether salivation was evoked by activating muscarinic receptors with methacholine, peptidergic receptors with substance P or physalaemin, or alpha-adrenoceptors with phenylephrine. Unilateral operation affected to some degree the contralateral gland also.