A Cluster Analysis of Oral and Cognitive Health Indicators: An Exploratory Study on Cholinergic Activity as the Link

INTRODUCTION

Poor oral health has been suggested as a risk factor for cognitive decline. Yet, biologically plausible mechanisms explaining this relationship remain unknown.

OBJECTIVES

We aimed (1) to identify oral and cognitive health clustering patterns among middle-aged to elderly Canadians and (2) to investigate the extent to which these patterns could be explained by bone mineral density (BMD), a proxy measure of the cholinergic neurons' activity.

METHODS

This cross-sectional study used baseline data from the Comprehensive cohort of the Canadian Longitudinal Study of Aging (CLSA). Oral health was assessed by a self-report questionnaire, and 7 task-based instruments measured cognitive health. We identified oral and cognitive health clusters, our outcome variables, using latent class analysis. Two sets of multivariate logistic regression and 95% confidence intervals were used to investigate whether BMD explains the odds of membership in a certain oral and cognitive health group. The final models were adjusted for socioeconomic, health, and lifestyle factors.

RESULTS

Our study sample (N = 25,444: 13,035 males, 12,409 females) was grouped into 5 and 4 clusters based on the oral health status and performance on the cognitive tasks, respectively. After adjusting for all potential covariates, increase in BMD was not associated with higher odds of membership in classes with better oral health (odds ratio [OR] = 1.58 [95% confidence interval {CI}: 0.85-2.92]) and cognitive health (OR = 1.61 [95% CI: 1-2.6]) compared with the groups with the least favorable oral and cognitive health status, respectively.

CONCLUSION

Middle-aged and elderly Canadians show different oral and cognitive health profiles, based on their denture-wearing status and performance on cognitive tests. No evidence could be found to support BMD in place of cholinergic neurons' activity as the common explanatory factor behind the association between oral health and cognitive health.

KNOWLEDGE TRANSFER STATEMENT

This study is probably the first of its kind to shed light on the cholinergic system as a potential pathway influencing oral and cognitive health. Our findings may support the notion that any potential association between poor oral health and cognitive health might be explained by common contributors, helping clinicians to find the common risk factors for both conditions.

A descriptive analysis of first trimester urinary concentrations of 14 bisphenol analogues in the MIREC Canadian pregnancy cohort

BACKGROUND

Concern over the health effects of BPA, particularly for the developing fetus, has led to an increasing use of bisphenol analogues in industrial and consumer products, which may be as hormonally active as BPA. Biomonitoring data for many bisphenol analogues, especially in pregnant populations, are limited.

METHODS

We measured concentrations of 14 bisphenol analogues in 1st trimester urine samples (n = 1851) from the Maternal-Infant Research on Environmental Chemicals (MIREC) Canadian pregnancy cohort (2008-2011). We examined patterns of exposure according to sociodemographic and sampling characteristics as well as occupation and frequency of consumption of canned fish within the previous 3 months.

RESULTS

BPA was detected in 89% of participants with a specific gravity standardized geometric mean concentration of 0.990 μg/L. Biphenol 4,4' (BP 4,4'), 4,4'-dihydroxydiphenyl ether (DHDPE), and bisphenol E (BPE) were detected in >97% of participants. Bisphenol F (BPF) and bisphenol S (BPS) were detected in >60% of participants. Specific gravity standardized geometric mean concentrations of these 5 compounds ranged from 0.024 to 0.564 μg/L. Nine bisphenol analogues were detected in <9% of participants. Concentrations of BP 4,4', DHDPE, and BPE were higher in younger women and those with higher pre-pregnancy BMI, lower household income, lower education, and among smokers. We found a similar pattern of differences in BPF for age, education, and smoking status while BPS similarly differed across categories of pre-pregnancy BMI. Participants who were unemployed or working in the service industry had higher molar sum of 7 bisphenol analogues than those working in healthcare, education, or an office setting. Canned fish consumption was not related to bisphenol analogue concentrations.

CONCLUSION

BP 4,4', DHDPE, BPE, BPF, and BPS were highly detected in 1st trimester urine samples in this large pan-Canadian pregnancy cohort. This suggests widespread exposure to these analogues around 2008-2011 and warrants further investigation into associations with health outcomes.

Immunoinflammatory processes: Overlapping mechanisms between obesity and eating disorders?

Obesity and eating disorders are conditions that involve eating behaviors and are sometimes comorbid. Current evidence supports alterations in immunoinflammatory processes in both obesity and eating disorders. A plausible hypothesis is that immunoinflammatory processes may be involved in the pathophysiology of obesity and eating disorders. The aim of this review is to highlight the link between obesity and eating disorders, with a particular focus on immunoinflammatory processes. First, the relation between obesity and eating disorders will be presented, followed by a brief review of the literature on their association with immunoinflammatory processes. Second, developmental factors will be discussed to clarify the link between obesity, eating disorders, and immunoinflammatory processes. Genetic and epigenetic risk factors as well as the potential roles of stress pathways and early life development will be presented. Finally, implications of these findings for future research are discussed. This review highlighted biological and developmental aspects that overlap between obesity and EDs, emphasizing the need for biopsychosocial research approaches to advance current knowledge and practice in these fields.

Interpersonal capitalization moderates the associations of chronic caregiving stress and depression with inflammation

Chronic stress and depression can enhance chronic low-grade inflammation. Interpersonal factors may buffer the impact of stress and depression on inflammation. Interpersonal capitalization is a social support process in which one discloses positive personal events and experiences to close others. Greater capitalization may attenuate the deleterious impact of chronic stress and depression. The goal of the current study was to assess whether interpersonal capitalization is associated with inflammation and whether it moderates the association of chronic stress and depression with inflammation. In this cross-sectional study of chronic caregiving stress, 222 caregiving mothers of adolescents with developmental disabilities or comparison mothers of typically developing adolescents completed a self-reported daily diary assessment of capitalization, the Center for Epidemiological Study-Depression scale, and provided blood samples to assess interleukin-6, tumor necrosis factor-α, and C-reactive protein, three circulating inflammatory markers. Regression analysis indicated that there was no main effect of capitalization on inflammation, p = .24, R² = .006. However, there was a significant three-way interaction among capitalization, chronic caregiving stress, and depressive symptoms, p = .01, R² = .02. Among participants with lower capitalization, greater depressive symptoms were associated with higher inflammation in the caregiving group, but not in the comparison group. Among participants with higher capitalization, greater depressive symptoms were no longer significantly associated with higher inflammation among caregivers, but were marginally related to inflammation in the comparison group. Capitalization may thus be an interpersonal process mitigating the effects of chronic stress and depression on inflammation.

Associations among oxytocin receptor gene (OXTR) DNA methylation in adulthood, exposure to early life adversity, and childhood trajectories of anxiousness

Recent models propose deoxyribonucleic acid methylation of key neuro-regulatory genes as a molecular mechanism underlying the increased risk of mental disorder associated with early life adversity (ELA). The goal of this study was to examine the association of ELA with oxytocin receptor gene (OXTR) methylation among young adults. Drawing from a 21-year longitudinal cohort, we compared adulthood OXTR methylation frequency of 46 adults (23 males and 23 females) selected for high or low ELA exposure based on childhood socioeconomic status and exposure to physical and sexual abuse during childhood and adolescence. Associations between OXTR methylation and teacher-rated childhood trajectories of anxiousness were also assessed. ELA exposure was associated with one significant CpG site in the first intron among females, but not among males. Similarly, childhood trajectories of anxiousness were related to one significant CpG site within the promoter region among females, but not among males. This study suggests that females might be more sensitive to the impact of ELA on OXTR methylation than males.

Cognitive Vulnerability to Depression in Adolescents with Depression, their Healthy Siblings and a Control Group: A Cross-sectional Study

Introduction

At least half of first depressive episode appear before adulthood. A negative cognitive bias is present among individuals who suffer from major depression. This bias is also reported among individuals at high risk of major depression (e.g. child of depressed mother). When present, cognitive vulnerability may predispose to major depression. No study to date aimed to evaluate the cognitive vulnerability of siblings of depressed individuals.

Objectives and aims

To review the principles behind cognitive vulnerability. To assess cognitive vulnerability in depressed adolescents, in healthy siblings and in a control group.

Methods

Eighty adolescents (27 adolescents treated for depression, 24 healthy siblings and 29 controls), aged between 12 and 20 years old, were recruited and assessed using validated measures of bio-psycho-social vulnerabilities. All diagnoses were confirmed using a K-SADS interview. Cortisol level samples were obtained through morning saliva. Cognitive vulnerability was assessed using self-report questionnaires (CES-D, LEIDS-R, EPQ) as well as computer-based tasks (Ekman's tasks of facial recognition and the movie for assessment of social cognition [MASC]). We translated the MASC from German to French. The parents of the adolescents also filled the LEIDSR and the CESD.

Results

The LEIDS-R presented a significant increase in certain subscales (hopelessness, aggression and rumination) compared to the healthy siblings and the controls. Interestingly, there was also a correlation between the LEIDS R results of the parents and of the depressed adolescent (r = 0.43, P = 0.04).

Conclusions

The LEIDSR appears to be the most sensitive task to detect cognitive vulnerability. A relation between the parent response and the depressed adolescent response could be found.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Association of Stress Hormone System, Epigenetics and Imaging

Introduction

Major depressive disorder (MDD) is a common psychiatric condition, affecting up to 350 million people worldwide. Its pathogenesis seems to involve dysregulation of the hypothalamic-pituitary (HPA) axis and inflammation as key elements of the condition. Stressful life events and in particular early life adversity seem to play an important role as risk factors for MDD. Epigenetic, which has been found to impact in the transcription of genes, seem to be associated with brain structure and function. Aim of the research was to provide an overview about neuroimaging (epi)-genetics in MDD.

Methods

Functional MRI, epigenetic and genetic information was obtained in a cohort of patients with MDD and healthy controls. Associations between, early life adversity, methylation of FKBP5 and SLC6A4, genetic variants and brain function and connectivity have been analysed.

Results

Higher methylation of SLC6A4 gene was associated with higher BOLD response during emotion processing and lower BOLD response during higher order cognitive processes. Healthy participants with higher SLC6A4 methylation involved prefrontal cortical regions to a greater extent than the participants with lower SLC6A4 methylation, when trying to switch attention away from negative emotional stimuli (Frodl et al., 2015). Moreover, FKBP5 methylation was association with HPA axis functioning and amygdala brain function in patients with MDD. FKBP5 methylation also was related to grey matter volume.

Conclusions

Our study provides further support to the hypothesis that DNA methylation plays a role. Particular peripheral DNA methylation states of MDD candidate genes are associated with brain function during emotion processing in patients with MDD.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Tooth Loss Increases the Risk of Diminished Cognitive Function

Emerging evidence suggests that oral health is associated with cognitive function. This review aims to systematically assess this association in adult populations via prospective cohort study designs. Eligible study reports were identified by searching the MEDLINE (via Ovoid), EMBASE, PsycoINFO, and Cochrane Library databases. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated with a random effects model. From 1,251 identified articles, 10 were included in the systematic review and 8 in the meta-analysis. Random effects analysis showed, with statistically low heterogeneity, that individuals with suboptimal dentition (<20 teeth) were at a 20% higher risk for developing cognitive decline (HR = 1.26, 95% CI = 1.14 to 1.40) and dementia (HR = 1.22, 95% CI = 1.04 to 1.43) than those with optimal dentition (≥20 teeth). Studies on the association between periodontal disease and cognitive status showed conflicting results. Within the limits of the quality of published evidence, this meta-analysis lends further support to the hypothesis that tooth loss is associated with an increased risk of cognitive impairment and dementia.

Knowledge Transfer Statement: Based on the published literature, the results of this study show that the risk for cognitive impairment and dementia increases with loss of teeth. This information adds to the evidence showing links between oral and general health and suggests that oral health strategies aimed to preserve teeth may be important in reducing risk of systemic disease.

Dopamine cross-sensitization between psychostimulant drugs and stress in healthy male volunteers

Dysregulation of the stress response system is a potential etiological factor in the development of and relapse to multiple neuropsychiatric disorders. Previously we reported that repeated intermittent d-amphetamine administration can lead to progressively greater dopamine release, thereby providing evidence of drug-induced neurochemical sensitization. Here, we test the hypothesis that repeated exposure to d-amphetamine increases dopaminergic responses to stress; that is, produces cross-sensitization. Using positron emission tomography, we measured in 17 healthy male volunteers (mean ± s.d. = 22.1 ± 3.4 years) [(11)C]raclopride binding responses to a validated psychosocial stress task before and 2 weeks after a regimen of repeated d-amphetamine (3 × 0.3 mg kg(-1), by mouth; n = 8) or placebo (3 × lactose, by mouth; n = 9). Mood and physiological measurements were recorded throughout each session. Before the d-amphetamine regimen, exposure to the stress task increased behavioral and physiological indices of stress (anxiety, heart rate, cortisol, all P ⩽ 0.05). Following the d-amphetamine regimen, the stress-induced cortisol responses were augmented (P < 0.04), and voxel-based analyses showed larger stress-induced decreases in [(11)C]raclopride non-displaceable binding potential across the striatum. In the placebo group, re-exposure to stress led to smaller clusters of decreased [(11)C]raclopride binding, primarily in the sensorimotor striatum (P < 0.05). Together, this study provides evidence for drug × stress cross-sensitization; moreover, random exposure to stimulants and/or stress cumulatively, while enhancing dopamine release in striatal areas, may contribute to a lowered set point for psychopathologies in which altered dopamine neurotransmission is invoked.

Dietary vitamin A intake and bone health in the elderly: the Rotterdam Study

BACKGROUND/OBJECTIVES

High vitamin A intake may be associated with a decreased bone mineral density (BMD) and increased risk of fractures. Our objectives were to study whether dietary intake of vitamin A (total, retinol or beta-carotene) is associated with BMD and fracture risk and if associations are modified by body mass index (BMI) and vitamin D.

SUBJECTS/METHODS

Participants were aged 55 years and older (n=5288) from the Rotterdam Study, a population-based prospective cohort. Baseline vitamin A and D intake was measured by a food frequency questionnaire. BMD was measured by dual-energy X-ray absorptiometry at four visits between baseline (1989-1993) and 2004. Serum vitamin D was assessed in a subgroup (n=3161). Fracture incidence data were derived from medical records with a mean follow-up time of 13.9 years.

RESULTS

Median intake of vitamin A ranged from 684 retinol equivalents (REs)/day (quintile 1) to 2000 REs/day (quintile 5). After adjustment for confounders related to lifestyle and socioeconomic status, BMD was significantly higher in subjects in the highest quintile of total vitamin A (mean difference in BMD (95% confidence interval (CI))=11.53 (0.37-22.7) mg/cm(2)) and retinol intake (mean difference in BMD (95% CI)=12.57 (1.10-24.05) mg/cm(2)) than in the middle quintile. Additional adjustment for BMI diluted these associations. Fracture risk was reduced in these subjects. Significant interaction was present between intake of retinol and overweight (BMI >25 kg/m(2)) in relation to fractures (P for interaction =0.05), but not BMD. Stratified analysis showed that these favourable associations with fracture risk were only present in overweight subjects (BMI >25 kg/m(2)). No effect modification by vitamin D intake or serum levels was observed.

CONCLUSIONS

Our results suggest a plausible favourable relation between high vitamin A intake from the diet and fracture risk in overweight subjects, whereas the association between vitamin A and BMD is mainly explained by BMI.

Tryptophan hydroxylase(2) gene polymorphisms predict brain serotonin synthesis in the orbitofrontal cortex in humans

Brain regional serotonin synthesis can be estimated in vivo using positron emission tomography (PET) and α-[((11))C]methyl-L-tryptophan ((11)C-AMT) trapping (K*) as a proxy. Recently, we reported evidence of lower normalized (11)C-AMT trapping in the orbitofrontal cortex (OBFC) of subjects meeting the criteria for an impulsive and/or aggressive behavioral phenotype. In this study, we examined whether part of the variance in OBFC serotonin synthesis is related to polymorphisms of the gene that encodes for the indoleamine's rate-limiting enzyme in the brain, tryptophan hydroxylase-2 (TPH(2)). In all, 46 healthy controls had PET (11)C-AMT scans and were genotyped for 11 single-nucleotide polymorphisms (SNPs) distributed across the TPH(2) gene and its 5' upstream region. Several TPH(2) SNPs were associated with lower normalized blood-to-brain clearance of (11)C-AMT in the OBFC. Dose-effect relationships were found for two variants (rs6582071 and rs4641527, respectively, located in the 5' upstream region and intron 1) that have previously been associated with suicide. Associations in the OBFC remained statistically significant in a mixed larger sample of patients and controls. These results suggest that in humans, genetic factors might partly account for variations in serotonin synthesis in the OBFC.

The effects of experimentally lowered serotonin function on emotional information processing and memory in remitted depressed patients

It has been well documented that acute tryptophan depletion (ATD) induces symptoms in remitted depressed patients treated with an SSRI. ATD also has effects on cognition, both in patients and in healthy samples. The exact nature of ATD-induced cognitive changes in depression remains unclear. It is also unclear whether cognitive effects can be induced through partial ('low-dose') depletion. The aim of this study is to investigate the differential effects of low-dose and high-dose ATD on emotional information processing and mood in remitted depressed patients. Eighteen remitted depressed patients received high-dose and low-dose ATD in a randomized, double-blind, within-subjects crossover design. Mood was assessed before and after administration of the depletion drink. Five hours after administration, patients conducted tests measuring neutral and emotional information processing. High-dose ATD increased depressive symptoms and induced a temporary depressive 'relapse' in half of the patients. High-dose ATD also decreased the recognition of fear and impaired learning and memory retrieval. The impaired learning occurred only in mood-responders. Low-dose ATD had no effects on mood but speeded the recognition of facial expressions of disgust. Accurate recognition of sad faces at baseline was associated with mood response to ATD. High-dose ATD leads to changes in memory and in the recognition of negative facial expressions in SSRI-treated remitted depressed patients. The effect of low-dose ATD on mood and cognition seems to be quite limited. Emotional information processing at baseline predicts mood-response to ATD.

Multi-level approach to anaesthetic effects produced by sevoflurane or propofol in humans: 1. BIS and blink reflex †

BACKGROUND

The relative roles of forebrain and brainstem in producing adequate anaesthesia are unclear.

METHODS

We simultaneously analysed the effects of sevoflurane (Group S; n = 18) or propofol (Group P; n = 29) on the bispectral index (BIS) and the first component of the blink reflex (R1). The dose of anaesthetic agent was increased until loss of blink reflex. After discontinuation and reappearance of blink reflex activity, the amount was increased again. The area under curve R1 (area-R1) of the electromyogram of the orbicularis oculi muscle after electrical stimulation of the supraorbital nerve was measured. Using a sigmoid E(max) model and a first-order rate constant k(e0), we characterized the dose-response relationships for BIS and area-R1.

RESULTS

Concentration-dependent depression of BIS and area-R1 was adequately modelled. The concentration that causes an effect midway between minimum and maximum (EC50) for area-R1 was smaller than EC50 for BIS in both groups [0.34 (0.19) vs 1.29 (0.19) vol% and 1.78 (0.65) vs 2.69 (0.67) mug ml(-1); mean (sd)]. At doses of sevoflurane and propofol with equivalent depression of BIS, sevoflurane depressed area-R1 more than propofol. The k(e0) for area-R1 was about half that for BIS in both groups: 0.24 (0.19-0.29) vs 0.48 (0.38-0.60) min(-1) for Group S; 0.28 (0.23-0.34) vs 0.46 (0.40-0.54) min(-1) for Group P, geometric mean (95% CI).

CONCLUSIONS

The blink reflex (brainstem function) is more sensitive to sevoflurane or propofol than BIS (forebrain function). Sevoflurane suppresses the blink reflex more than propofol. Different k(e0)s for blink reflex vs BIS indicate different effect sites.

Multi-level approach to anaesthetic effects produced by sevoflurane or propofol in humans: 2. BIS and tetanic stimulus-induced withdrawal reflex †

BACKGROUND

General anaesthesia could be assessed at two sites: cortical structures and the spinal cord. However, the practicalities of measurement at these two sites differ substantially.

METHODS

We simultaneously analysed effects of sevoflurane (Group S; n = 16) or propofol (Group P; n = 17) on bispectral index (BIS) and the tetanic stimulus-induced withdrawal reflex (TIWR). TIWR was quantified by the area under the curve of the electromyogram of the biceps femoris muscle after electrical stimulation of the sural nerve. After loss of consciousness, TIWR was evoked once per minute. The anaesthetic was increased until TIWR disappeared. After discontinuation of the anaesthetic and reappearance of TIWR, the amount of anaesthetic was increased again. Using a sigmoid E(max) model and a first-order rate constant k(e0), we characterized the dose-response relationships for BIS and TIWR.

RESULTS

Concentration-dependent depression of TIWR was reasonably well modelled for sevoflurane, but poorly for propofol. TIWR was completely suppressed by sevoflurane, but not propofol. Sevoflurane reduced TIWR to 5 mV ms (very weak movement) at 1.68 vol% end-expired concentration [approximately minimum alveolar concentration (MAC value)]. The k(e0)s for TIWR were smaller than those for BIS: 0.25 (0.16-0.39) vs 0.41 (0.33-0.51) min(-1) for Group S; 0.25 (0.22-0.30) vs 0.34 (0.29-0.40) min(-1) for Group P [geometric mean (95% CI)].

CONCLUSIONS

High concentrations of sevoflurane depress TIWR more than propofol. With propofol, we frequently observed a paradoxical behaviour of muscles of the lower leg. TIWR lags behind BIS, indicating different effect sites for two intended anaesthetic effects: unresponsiveness to noxious stimulation and unconsciousness.

Acute prefrontal cortex TMS in healthy volunteers: Effects on brain 11C-αMtrp trapping

High-frequency repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (LDLPFC) is a technique with purported efficacy as a treatment for major depression. Here, we assessed in vivo, in healthy volunteers, the effect of acute rTMS of the LDLPFC, relative to the stimulation of the left occipital cortex (LOC), on brain regional serotonin synthesis capacity, using the [(11)C]-alpha-methyl-tryptophan ((11)C-alphaMtrp)/PET method. Ten subjects were studied twice, once following rTMS of the LDLPFC and once following rTMS of the LOC in a randomized counterbalanced order. Three blocks of 15 trains of 10 Hz rTMS were delivered 10 min apart. Behavioural and autonomic measures were recorded before and after each rTMS session. Comparisons of TMS-related changes in regional normalized brain uptake and trapping of (11)C-alphaMtrp (K*) values were carried out using SPM99. Statistically significant regional differences were identified on the basis of an extent threshold of 50 voxels, with a peak threshold of p=0.005 uncorrected. Behavioural and autonomic measures were unaffected by rTMS. Relative to LOC stimulation, LDLPFC rTMS was associated with marked changes in normalized K* in limbic areas, with significantly lower values in the left parahippocampal gyrus (BA 28) and the right insula (BA 13), and higher values in the right cingulate gyrus (BA 31) and cuneus (BA 18). These findings indicate that acute rTMS of the LDLPFC in healthy volunteers modulates aspects of tryptophan/5-HT metabolism in limbic areas. Such adaptive changes may contribute to the mechanism of action of prefrontal rTMS in major depression.

Electromyographic assessment of blink reflexes correlates with a clinical scale of depth of sedation/anaesthesia and BIS during propofol administration

BACKGROUND

General anaesthesia is characterized by loss of consciousness, amnesia and obtundation of reflex responses to noxious stimuli. Quantifying the blink reflex may reflect the depression of reflex arches induced by anaesthetics and thus being informative on the anaesthetic state.

METHODS

The relation between the electrically evoked blink reflexes and the depth of sedation and anaesthesia induced with intravenous propofol was investigated. Twenty patients received propofol by target-controlled infusion to create a stepwise deepening of sedation and anaesthesia. Depth of anaesthesia was assessed using the observer's assessment of anaesthesia and sedation (OAAS) scale, and by bispectral EEG analysis (BIS). Probit analysis was used to estimate the predicted propofol effect site concentrations producing unconsciousness, no response to noxious stimulation, and loss of blink reflex components.

RESULTS

Latency of the first (R1) and second (R2) blink component increased, whereas duration and area decreased with increasing depth of sedation and anaesthesia. A reasonably strong correlation between OAAS and the areas of R1 and R2 components was found (Spearman's rho = 0.92 and 0.89). The areas of R1 and R2 and the OAAS also correlated with BIS (Spearman's rho = 0.91, 0.88 and 0.90). EC(50) and EC(95) for loss of R1 were 2.8 (95% CI: 2.5-3.2) micro g/ml and 4.6 (95% CI: 4.1-5.5) micro g/ml, respectively.

CONCLUSIONS

Our results suggest that the differential sensitivity of the components of the blink reflex could be useful in monitoring depth of sedation and light levels of anaesthesia during the administration of propofol. Both OAAS and BIS correlate similarly with the blink reflex components.

Monoamine depletion in psychiatric and healthy populations: review

A number of techniques temporarily lower the functioning of monoamines: acute tryptophan depletion (ATD), alpha-methyl-para-tyrosine (AMPT) and acute phenylalanine/tyrosine depletion (APTD). This paper reviews the results of monoamine depletion studies in humans for the period 1966 until December 2002. The evidence suggests that all three interventions are specific, in terms of their short-term effects on one or two neurotransmitter systems, rather than on brain protein metabolism in general. The AMPT procedure is somewhat less specific, affecting both the dopamine and norepinephrine systems. The behavioral effects of ATD and AMPT are remarkably similar. Neither procedure has an immediate effect on the symptoms of depressed patients; however, both induce transient depressive symptoms in some remitted depressed patients. The magnitude of the effects, response rate and quality of response are also comparable. APTD has not been studied in recovered major depressive patients. Despite the similarities, the effects are distinctive in that ATD affects a subgroup of recently remitted patients treated with serotonergic medications, whereas AMPT affects recently remitted patients treated with noradrenergic medications. The evidence also suggests that ATD and APTD affect different cognitive functions, in particular different memory systems. Few studies investigated cognitive effects of the procedures in patients. Patients who are in remission for longer may also be vulnerable to ATD and AMPT, but the relationship with prior treatment is much weaker. For these patients, individual vulnerability markers are the more important determinants of depressive response, making these techniques potentially useful models of vulnerability to depression.

Electromyographic assessment of blink and corneal reflexes during midazolam administration: useful methods for assessing depth of anesthesia?

BACKGROUND

There are at least three components of the anesthetic state: loss of consciousness, amnesia and obtundation of reflex responses to noxious stimuli. To investigate the third component, we used a standard electrical stimulus to evoke a blink reflex, which was electromyographically recorded. These data may give information on the anesthetic state.

METHODS

The relation between the electrically evoked blink and corneal reflexes and the depth of sedation and anesthesia induced with intravenous midazolam was investigated. Ten patients received i.v. increments of midazolam (1 mg, 2 mg, 3 mg, 3 mg, 3 mg, etc., until a 21-mg total dose) to create a step-wise deepening of sedation and anesthesia. Depth of anesthesia was assessed by the Observer's Assessment of Alertness/Sedation (OAAS) scale, ranging from 5 ( = awake and alert) to 0 ( = no motor response to tetanic stimulation).

RESULTS

Latency of the first (R1) and second (R2) blink components and the corneal (C) reflex component increased, whereas duration and area decreased with increasing depth of sedation and anesthesia. R1 was last seen at an OAAS score [mean (SD)] of 1.8 (0.8), R2 at a score of 3.1 (1.1), C at a score of 3.8 (0.8), and R3 at 4.8 (0.5). These end-points were all statistically different from each other, except R2 vs. C.

CONCLUSIONS

Our results suggest that the differential sensitivity of the components of the blink reflex could be useful to monitor depth of sedation and light levels of anesthesia during the administration of midazolam.

The dose-response and time-effect relationships of intrathecal bupivacaine in rats. The influence of epinephrine and pH

The present study defined the dose-response relationship of intrathecally injected bupivacaine in rats. The effect was a quantified drug-induced and graded reduction in the magnitude of the withdrawal reflexes elicited by transcutaneous electrical stimulation. Intrathecal epinephrine reduced the magnitude of the withdrawal reflexes. The combination of epinephrine and bupivacaine resulted in a dose-response relationship different from that of bupivacaine alone, and the combination was more effective than bupivacaine alone. The intrathecal combinations of bupivacaine and 25 micrograms of the alpha 2-adrenergic antagonist idazoxan had an effect not different from that of bupivacaine alone, but the duration of effect was shorter. The dose-response relationship of bupivacaine was not different whether the pH of the solution was 4.4 or 6.1. The results concerning the effect as a function of time confirm those of earlier studies: 1) the duration of effect depends on the dose of bupivacaine; 2) epinephrine protracts the duration of effect; 3) the pH is of no relevance. Thermal tests for nociception showed that antinociception outlasted motor symptoms. Epinephrine enhanced this effect of bupivacaine, but did not change the duration of motor impairment.