Comparison of diphenhydramine and modafinil on arousal and autonomic functions in healthy volunteers

No evidence for a modulating effect of continuous transcutaneous auricular vagus nerve stimulation on markers of noradrenergic activity

Although transcutaneous auricular vagus nerve stimulation (taVNS) is thought to increase central noradrenergic activity, findings supporting such mechanism are scarce and inconsistent. This study aimed to investigate whether taVNS modulates indirect markers of phasic and tonic noradrenergic activity. Sixty-six healthy participants performed a novelty auditory oddball task twice on separate days: once while receiving taVNS (left cymba concha), once during sham (left earlobe) stimulation. To maximize potential effects, the stimulation was delivered continuously (frequency: 25 Hz; width: 250 μs) at an intensity individually calibrated to the maximal level below pain threshold. The stimulation was administered 10 min before the oddball task and maintained throughout the session. Event-related pupil dilation (ERPD) to target stimuli and pre-stimulus baseline pupil size were assessed during the oddball task as markers of phasic and tonic noradrenergic activity, respectively. Prior to and at the end of stimulation, tonic pupil size at rest, cortisol, and salivary alpha-amylase were assessed as markers of tonic noradrenergic activity. Finally, we explored the effect of taVNS on cardiac vagal activity, respiratory rate, and salivary flow rate. Results showed a greater ERPD to both target and novelty compared to standard stimuli in the oddball task. In contrast to our hypotheses, taVNS did not impact any of the tested markers. Our findings strongly suggest that continuous stimulation of the cymba concha with the tested stimulation parameters is ineffective to increase noradrenergic activity via a vagal pathway.

Predicting the effectiveness of engagement and disengagement emotion regulation based on emotional reactivity in borderline personality disorder

Improving emotion regulation is central to borderline personality disorder (BPD) treatment, but little research indicates which emotion regulation strategies are optimally effective and when. Basic emotion science suggests that engagement emotion regulation strategies that process emotional content become less effective as emotional intensity increases, whereas disengagement strategies that disengage from it do not. This study examined whether emotional reactivity to emotional stimuli predicts the effectiveness of engagement and disengagement emotion regulation across self-report, general physiologic (heart rate), sympathetic (skin conductance responses), and parasympathetic (respiratory sinus arrythmia) emotion in BPD, healthy, and clinical control (i.e. generalized anxiety disorder; GAD) groups. 120 participants (40 per group) were exposed to emotion inductions and then instructed to implement engagement (mindful awareness) and disengagement (distraction) strategies while self-report and physiological emotion measurements were taken. In the BPD and GAD groups, higher heart rate or respiratory sinus arrythmia reactivity, respectively, predicted improved mindful awareness effectiveness. Higher skin conductance reactivity predicted worsened distraction effectiveness in BPD. Higher reactivity may potentiate engagement emotion regulation, and exacerbate disengagement from emotional content, in BPD. Future research should examine other domains of emotion regulation that may be influenced by emotional intensity, and other forms of emotional intensity that may influence them.

Improvement of lupus-associated fatigue with modafinil: Report of two cases

Fatigue is a frequently reported and disabling symptom in patients with systemic lupus erythematosus (SLE). The management of Lupus-associated fatigue (LAF) is complex and requires the exclusion of disease activity and comorbidities as potentially treatable causes. Standard of care recommendations includes psychological counselling and regular physical activity. However, many SLE patients still report the persistence of LAF despite these measures. Therefore, pharmacological management may be required, which has been insufficiently investigated in clinical trials. Here, we report two patients who improved with pharmacological treatment with modafinil (MODA), a central nervous system stimulant. Both patients had an overall low disease activity (SLEDAI-2K score of 0). Their FACIT fatigue scores were 15 and 20, respectively (with a maximum score of 52, where 52 indicates the best quality of life). With MODA treatment, the first patient's FACIT fatigue score improved from 15 to 42, the second patient's score from 20 to 37. In the latter patient, it returned to 21 after stopping the drug and increased back again to 37 after re-treatment.In conclusion, our report demonstrates, for the first time, that MODA treatment is a potential pharmacological treatment option in selected patients with LAF. Clinical trials in SLE are required to confirm our observations.

Resting and Functional Pupil Response Metrics Indicate Features of Reward Sensitivity and ASD in Children

The current study examined the relationship between quantitative measures of reward and punishment sensitivity, features of autism spectrum disorder (ASD), and resting and functional pupil response metrics across a clinically heterogeneous sample. Scores on a parent-report measure of punishment and reward sensitivity were correlated with ASD features. We also assessed whether pupil measurements could be used as a physiologic correlate of reward sensitivity and predictor of ASD diagnosis. In a logistic regression model, pupil dilation metrics, sex, and IQ, correctly classified 86.3% of participants as having an ASD diagnosis versus not. This research highlights individual differences of reward sensitivity associated with ASD features. Results support the use of pupil metrics and other patient-level variables as predictors of ASD diagnostic status.

Moving beyond belief: A narrative review of potential biomarkers for transcutaneous vagus nerve stimulation

Transcutaneous vagus nerve stimulation (tVNS) is a non-invasive neurostimulation technique that is currently being tested as a potential treatment for a myriad of neurological and psychiatric disorders. However, the working mechanisms underlying tVNS are poorly understood and it remains unclear whether stimulation activates the vagus nerve for every participant. Finding a biological marker of tVNS is imperative, as it can help guide research on clinical applications and can inform researchers on optimal stimulation sites and parameters to further optimize treatment efficacy. In this narrative review, we discuss five potential biomarkers for tVNS and review currently available evidence for these markers for both invasive and tVNS. While some of these biomarkers hold promise from a theoretical perspective, none of the potential biomarkers provide clear and definitive indications that tVNS increases the vagal activity or augments activity in the locus coeruleus-noradrenaline network. We conclude the review by providing several recommendations for how to tackle the challenges and opportunities when researching potential biomarkers for the effects of tVNS.

Drug-Induced Hypertension

Untoward side effects of pharmaceuticals can result in considerable morbidity and expense to the health care system. There is likely a sizable fraction of the hypertensive population with disease either induced or exacerbated by polypharmacy. The elevation of blood pressure in drug-induced hypertension occurs through a variety of mechanisms, most notably, sodium and fluid retention, activation of the renin-angiotensin-aldosterone system, alteration of vascular tone, or a combination of these pathways. Recognition of common medications causing drug-induced hypertension is important to effectively control blood pressure. The epidemiology, pathophysiology, and management of these agents are discussed.

Use your words: The role of emotion labeling in regulating emotion in borderline personality disorder

Borderline personality disorder (BPD) treatments emphasize emotion labeling to decrease negative emotion and facilitate emotion regulation. However, no studies have examined emotion labeling in BPD or its impact on intentional emotion regulation. The present study examined the impact of emotion labeling on emotion and intentional emotion regulation attempts across self-reported and physiological indices (i.e., skin conductance response [SCR], respiratory sinus arrhythmia [RSA]) in BPD and healthy control (HC) groups. Participants listened to emotionally-evocative scripts and were either instructed to type the emotions that they were experiencing (labeling) or the objects they could imagine seeing in the script (control) into a computer. Following this, they were instructed to use either mindfulness or cognitive reappraisal to decrease their emotion. Self-reported, RSA, and SCR indices of negative emotion were collected throughout and analyzed using generalized estimating equations. Findings indicated that the BPD group experienced higher RSA during emotion labeling compared to the control task, but the HC group did not. HCs reported lower negative emotion after emotion labeling when implementing both emotion regulation strategies compared to the control task, but the BPD group did not. These findings suggest that emotion labeling may activate emotion regulatory systems in BPD and can potentiate intentional emotion regulation in HCs.

Functional Organization of the Sympathetic Pathways Controlling the Pupil: Light-Inhibited and Light-Stimulated Pathways

Pupil dilation is mediated by a sympathetic output acting in opposition to parasympathetically mediated pupil constriction. While light stimulates the parasympathetic output, giving rise to the light reflex, it can both inhibit and stimulate the sympathetic output. Light-inhibited sympathetic pathways originate in retina-receptive neurones of the pretectum and the suprachiasmatic nucleus (SCN): by attenuating sympathetic activity, they allow unimpeded operation of the light reflex. Light stimulates the noradrenergic and serotonergic pathways. The hub of the noradrenergic pathway is the locus coeruleus (LC) containing both excitatory sympathetic premotor neurones (SympPN) projecting to preganglionic neurones in the spinal cord, and inhibitory parasympathetic premotor neurones (ParaPN) projecting to preganglionic neurones in the Edinger-Westphal nucleus (EWN). SympPN receive inputs from the SCN via the dorsomedial hypothalamus, orexinergic neurones of the latero-posterior hypothalamus, wake- and sleep-promoting neurones of the hypothalamus and brain stem, nociceptive collaterals of the spinothalamic tract, whereas ParaPN receive inputs from the amygdala, sleep/arousal network, nociceptive spinothalamic collaterals. The activity of LC neurones is regulated by inhibitory α₂-adrenoceptors. There is a species difference in the function of the preautonomic LC. In diurnal animals, the α₂-adrenoceptor agonist clonidine stimulates mainly autoreceptors on SymPN, causing miosis, whereas in nocturnal animals it stimulates postsynaptic α₂-arenoceptors in the EWN, causing mydriasis. Noxious stimulation activates SympPN in diurnal animals and ParaPN in nocturnal animals, leading to pupil dilation via sympathoexcitation and parasympathetic inhibition, respectively. These differences may be attributed to increased activity of excitatory LC neurones due to stimulation by light in diurnal animals. This may also underlie the wake-promoting effect of light in diurnal animals, in contrast to its sleep-promoting effect in nocturnal species. The hub of the serotonergic pathway is the dorsal raphe nucleus that is light-sensitive, both directly and indirectly (via an orexinergic input). The light-stimulated pathways mediate a latent mydriatic effect of light on the pupil that can be unmasked by drugs that either inhibit or stimulate SympPN in these pathways. The noradrenergic pathway has widespread connections to neural networks controlling a variety of functions, such as sleep/arousal, pain, and fear/anxiety. Many physiological and psychological variables modulate pupil function via this pathway.

Modafinil Reduces Parasympathetic Activity but Does Not Influence Autonomic Reactivity to Orthostatic Load in Narcolepsy Type 1

INTRODUCTION

Modafinil may affect autonomic functions in healthy subjects. The aim of the study was to assess the long-term modafinil administration influence on the cardiac autonomic reactivity to orthostatic load in patients with narcolepsy type 1.

METHODS

In 15 patients (4 male; 11 female; median age, 47 years; range, 18-70 years) with narcolepsy type 1 treated with modafinil in daily dose of 100 to 300 mg, the short-term spectral analysis of heart rate variability (HRV) in supine-standing-supine test was performed before and after 72 hours of modafinil discontinuation.

RESULTS

The sympathovagal reactivity to orthostatic load was not modified by modafinil treatment; nevertheless, the parasympathetic activity expressed by length of R-R interval and high-frequency component of HRV is reduced in supine position in patients taking modafinil.

CONCLUSIONS

We conclude that long-term use of modafinil does not influence the cardiac autonomic reactivity to orthostatic load expressed by the HRV changes in supine-standing-supine test in narcolepsy type 1 patients, but the parasympathetic cardiac activity may be reduced in quiet supine position in patients with narcolepsy taking modafinil.

Heart rate variability and critical flicker fusion frequency changes during and after parachute jumping in experienced skydivers

PURPOSE

The purpose of this study was (1) to further explore the heart rate dynamics and assess a potential cardiovascular risk in response to 4000 m jumps in experienced skydivers; (2) to assess whether there is an impact of such jumps on skydivers' cortical arousal or not, which may impact their decision making processes.

METHOD

18 experienced skydivers performed successive jumps from a plane at 4000 m of height. Heart rate dynamics and cortical arousal were assessed by the use of heart rate variability and Critical Flicker Fusion Frequency (CFFF), respectively.

RESULTS

CFFF did not differ between the three measurement time points (p > 0.05). Mean heart rate increased during the jump (p < 0.001) and came back to pre-jump values after the jump (p < 0.001). Percentage of the differences of successive NN intervals greater than 50 ms (pNN50) decreased during the jump (p < 0.001) and kept lower values after the jump compared to pre-jump (p < 0.05). High-frequency power (HF) did not differ during the jump (p > 0.05) but decreased after the jump compared to both pre-jump (p < 0.01) and jump (p < 0.05). Sample entropy decreased during the jump (p < 0.001) and came back to pre-jump values after the jump (p > 0.05).

CONCLUSION

These results confirm a vagal input reduction associated with a rise of the sympathetic tone during the jump and suggests that the experienced skydiver is not exposed to a high cardiovascular risk. This study also shows that environmental stresses induced by free fall could not hamper the perceptual vigilance of experienced skydivers.

Agomelatine but not melatonin improves fatigue perception: a longitudinal proof-of-concept study

Chronic Fatigue Syndrome (CFS) represents a disabling condition characterized by persistent mental and physical fatigue, bodily discomfort and cognitive difficulties. To date the neural bases of CFS are poorly understood; however, mono-aminergic abnormalities, sleep-wake cycle changes and prefrontal dysfunctions are all thought to play a role in the development and maintenance of this condition. Here we explored in a group of 62 CFS subjects the impact on fatigue levels of agomelatine, an antidepressant with agonist activity at melatonin receptors (MT1 and MT2) and antagonist activity at serotoninergic 2C receptors (5HT2C). To tease out the relative effects of MT-agonism and 5HT2C antagonism on fatigue, we compared agomelatine 50mg u.i.d. with sustained release melatonin 10mg u.i.d. in the first 12-week-long phase of the study, and then switched all melatonin-treated subjects to agomelatine in the second 12-week-long phase of the study. Agomelatine treatment, but not melatonin, was associated with a significant reduction of perceived fatigue and an increase in perceived quality of life. Moreover the switch from melatonin to agomelatine was associated with a reduction of fatigue levels. Agomelatine was well tolerated by all enrolled subjects. Our data, albeit preliminary, suggest that agomelatine treatment could represent a novel useful approach to the clinical care of subjects with CFS.

Autonomic testing of women with interstitial cystitis/bladder pain syndrome

Purpose

Interstitial cystitis/bladder pain syndrome (IC/BPS) is characterized by urinary urgency, frequency, nocturia, pain worse as the bladder fills and improved after emptying. These features might suggest abnormal autonomic bladder control mechanisms. We compared the structural integrity of the autonomic nervous system (ANS) in IC/BPS and control subjects.

Methods

IRB-approved study at University Hospitals Case Medical Center, Cleveland, OH to evaluate the structural integrity of the ANS in adult females. Testing included cardiovascular response to deep breathing, Valsalva maneuver, 30 min head up tilt, and sudomotor test.

Results

Differences in ANS integrity for IC/BPS subjects and controls were determined by modified Composite Autonomic Severity Score (CASS) that includes sudomotor, adrenergic and cardiovascular indices. Baseline heart rate (HR) and HRs from each of three 10 min upright segments of a tilt test were compared and trend analyses performed using t tests. Healthy and IC/BPS subjects were demographically similar. The two groups did not differ in modified-CASS scores but elevated average peak heart rate was evident during baseline (supine; p = 0.057) for IC/BPS subjects prior to a tilt test. Difference at baseline was maintained at each interval during the tilt, with nearly identical slopes across intervals. The preliminary nature of this report denotes a small sample size and important differences may not be detected.

Conclusions

The findings show no structural ANS abnormalities in IC/BPS subjects. Higher baseline HR supports the concept of functional rather than structural change in the ANS, such as abnormality of sympathetic/parasympathetic balance that will require further evaluation.

Stimulus parameters for multifocal pupillographic objective perimetry

PURPOSE

We compared the diagnostic power of 10 stimulus variants that assessed the visual fields of both eyes by recording pupillary responses to multifocal stimuli. The 10 variants comprised 6 initial tests, and 4 subsequent variants whose design was informed by the initial results.

METHODS

Two study groups containing 16 normal and 22 primary open angle glaucoma subjects, and 15 normal and 20 primary open angle glaucoma subjects had their diagnostic status verified by a slit-lamp investigation, applanation tonometry, 3 forms of perimetry, and Stratus OCT. Stereoscopically arranged displays presented multifocal stimulus arrays having 24 stimulus regions/eye within the central 60 degrees. Pupil responses were recorded by video cameras under infrared illumination. The 10 stimulus conditions varied in presentation rate, duration, stimulus luminance, and flicker rate. Stimuli were 4 minutes in duration, presented in 8 segments of 30 seconds. Up to 15% of the data of a segment could be lost owing to blinks and fixation losses without repeating the segment.

RESULTS

Each recording gave 96 direct and consensual responses/subject. The best performing stimulus method gave a sensitivity of 1.0 ± 0.0 (mean ± SE) for moderate and severe glaucomatous fields combined at a false positive rate of 0.05. Median signal to noise ratios for peak response amplitude expressed as t-statistics exceeded 4 for several variants.

CONCLUSIONS

Stimulus delivery rates of about 1 presentation/region/s and test luminance around 150 cd/m performed best diagnostically. Unlike automated perimetry, the mfPOP method provides information on response delays and afferent and efferent defects at each region of the visual field.

Association of a deficit of arousal with fatigue in multiple sclerosis: effect of modafinil

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system, leading to chronic disability. Fatigue is a common and distressing symptom of MS which is unrelated to its clinical form, stage of development, the degree of disability, or the lesion load on magnetic resonance imaging. Fatigue in MS is associated with excessive daytime sleepiness and autonomic dysfunction. Recently it has been reported that the wakefulness-promoting drug modafinil may relieve fatigue in MS patients and ameliorate the associated cognitive difficulties. However, it is not clear to what extent the anti-fatigue effect of modafinil may be related to its alerting and sympathetic activating effects. We addressed this question by comparing three groups of subjects, MS patients with fatigue, MS patients without fatigue and healthy controls, matched for age and sex, on measures of alertness (self-ratings on the Epworth and Stanford Sleepiness Scales and on a battery of visual analogue scales; critical flicker fusion frequency; Pupillographic Sleepiness Test; choice reaction time) and autonomic function (systolic and diastolic blood pressure, heart rate, pupil diameter), and by examining the effect of a single dose (200 mg) of modafinil on these measures. MS patients with fatigue, compared with healthy controls, had reduced level of alertness on all the tests used; MS patients without fatigue did not differ from healthy controls. MS patients with fatigue had a reduced level of cardiovascular sympathetic activation compared to the other two groups. Modafinil displayed alerting and sympathomimetic effects in all three groups of subjects. As fatigue in MS is associated with reduced levels of alertness and sympathetic activity, modafinil may exert its anti-fatigue effect in MS by correcting these deficiencies. The anti-fatigue effect of modafinil may reflect the activation of the noradrenergic locus coeruleus (LC), since there is evidence that this wakefulness-promoting nucleus is damaged in MS, and that modafinil, probably via the dopaminergic system, can stimulate the LC. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Pupil and salivary indicators of autonomic dysfunction in autism spectrum disorder

Dysregulated tonic pupil size has been reported in autism spectrum disorder (ASD). Among the possible sources of this dysregulation are disruptions in the feedback loop between norepinephrine (NE) and hypothalamic systems. In the current study, we examined afternoon levels of salivary alpha-amylase (sAA, a putative correlate of NE) and cortisol (used to assess stress-based responses) in two independent samples of children with ASD. We found a larger pupil size and lower sAA levels in ASD, compared to typical and clinical age-matched controls. This was substantiated at the individual level, as sAA levels were strongly correlated with tonic pupil size. Relatively little diurnal variation in sAA taken in the home environment in the ASD group was also observed, while typical controls showed a significant linear increase throughout the day. Results are discussed in terms of potential early biomarkers and the elucidation of underlying neural dysfunction in ASD.

Enantiomeric separation and determination of the enantiomeric impurity of armodafinil by capillary electrophoresis with sulfobutyl ether-β-cyclodextrin as chiral selector

A selective capillary electrophoresis method using sulfobutyl ether-β-cyclodextrin as a chiral selector was developed and validated for the determination of the enantiomeric impurity of (R)-modafinil, i.e., armodafinil. Several parameters were optimized for a satisfactory enantioresolution, including the type and concentration of chiral selector and organic modifier, pH of background electrolyte (BGE), capillary temperature. The finally adopted condition was: 20 mmol/L phosphate buffer at pH 7.5, containing 20 mmol/L sulfobutyl ether-β-cyclodextrin and 20% methanol, at temperature of 25 °C. A good resolution of 3.3 for the two enantiomers of modafinil was achieved by applying the optimal conditions. The limit of detection (LOD) and limit of quantification (LOQ) of (S)-modafinil were 1.25 μg/mL and 2.50 μg/mL, respectively. The established method was also proven to display good selectivity, repeatability, linearity and accuracy. Finally, the method was used to investigate the enantiomeric purity of armodafinil in bulk samples.

Histamine H1 receptor antagonist cetirizine impairs working memory processing speed, but not episodic memory

BACKGROUND AND PURPOSE

The histaminergic neurotransmitter system is currently under investigation as a target for drug treatment of cognitive deficits in clinical disorders. The therapeutic potential of new drugs may initially be screened using a model of histaminergic dysfunction, for example, as associated with the use of centrally active antihistamines. Of the selective second generation antihistamines, cetirizine has been found to have central nervous system effects. The aim of the present study was to determine whether cetirizine can be used as a tool to model cognitive deficits associated with histaminergic hypofunction.

EXPERIMENTAL APPROACH

The study was conducted according to a three-way, double-blind, cross-over design. Treatments were single oral doses of cetirizine 10 and 20 mg and placebo. Effects on cognition were assessed using tests of word learning, memory scanning, vigilance, divided attention, tracking and visual information processing speed.

KEY RESULTS

Cetirizine 10 mg impaired tracking performance and both doses impaired memory scanning speed. None of the other measures indicated impaired performance.

CONCLUSION AND IMPLICATIONS

Cetirizine affects information processing speed, but these effects were not sufficient to serve as a model for cognitive deficits in clinical disorders.

Cognitive domains affected by histamine H(1)-antagonism in humans: a literature review

The neurotransmitter histamine has been suggested to be involved in cognitive functioning. Generally, studies in animals have shown a decrease in performance after decreasing histamine neurotransmission and improved performance after increasing histamine neurotransmission. It is unclear, however, what role histamine plays in cognition in humans. Up until now, most data are derived from studies and reviews that aimed to assess the sedative potential of H(1)-antagonists and not the effects on cognition in particular. The objective of this paper is specifically to review which cognitive domains are affected by H(1)-antagonists. Taken together, 90 experimental studies on the performance effects of sedative H(1)-antagonists published between 1973 and 2009 were reviewed. Results showed that psychomotor skills and attention are most frequently impaired and memory the least. Tasks assessing memory that were affected usually required rapid responses. It was concluded that both the complexity of the task as well as the demand for information processing speed determines the sensitivity to the effects of central H(1)-antagonism. The importance of the sensitive cognitive domains to histaminergic dysfunction, as well as the relation between histamine related decrease in arousal and task performance deserve further research.

Multifocal pupillographic visual field testing in glaucoma

PURPOSE

This preliminary study investigated a means of concurrently assessing the visual field defects of both eyes by recording pupillary responses to multifocal stimuli.

METHODS

Twenty normal subjects and 26 primary open angle glaucoma patients, age and sex matched, were examined by slit-lamp, Humphrey Field Analyser II achromatic 24-2 perimetry and fundus photography. The patients had moderate to severe fields in at least one eye. Two stereoscopically arranged displays presented an array of 24 stimulus regions per eye extending from fixation to 30 degrees eccentricity. Pupil responses were recorded by video cameras under infrared illumination. Four stimulus conditions were tested: each stimulus region containing either a single or a 2 x 2 array of patches, presented either steadily for 133 ms or flickered at 15 Hz for 266 ms. Mean presentation rate was 1/s/region. The 4-min duration stimuli were presented in 8 segments of 30 s. Segments did not need to be repeated unless more than 15% of a segment record was lost as a result of blinks or fixation losses.

RESULTS

The 48 stimuli produced 96 direct and consensual responses per subject. The single patch, non-flickered stimulus condition produced the best diagnostic performance, an area under the curve of 84%. The contraction amplitudes for that stimulus gave a median z-score of 3.2.

CONCLUSIONS

The method produced diagnostic accuracy approaching that of automated perimetry, but unlike perimetry provides standard errors for every point in each field as well as information on response delay and efferent defects. Only one pupil needs to function to measure both visual fields.

Comparison of ketanserin, buspirone and propranolol on arousal, pupil size and autonomic function in healthy volunteers

RATIONALE

The human pupil may be a suitable physiological test system for the assessment of excessive daytime sleepiness (EDS), but pupillometric assessment could be confounded by medication for comorbid hypertension and mood disorders.

OBJECTIVES

We examined the profile of the 5HT-2/alpha1/H1 antagonist ketanserin, the 5HT1a agonist buspirone and the beta adrenoceptor antagonist propranolol on pupillary and other measures of arousal.

MATERIALS AND METHODS

Ketanserin (20 mg), buspirone (10 mg) and propranolol (40 mg) were administered in three independent experiments according to a crossover, placebo-controlled, double-blind design. Resting pupil diameter (RPD) was sampled over 5-min in darkness with infrared pupillometry. Tests also included critical flicker fusion frequency (CFFF), visual analogue scales (VAS), the pupillary light reflex and heart rate/blood pressure.

RESULTS

Ketanserin reduced RPD, CFFF, VAS-rated arousal and blood pressure and increased the light reflex amplitude. Buspirone reduced RPD and blood pressure. Propranolol reduced heart rate but had no effects on pupillary functions or any arousal measure.

CONCLUSIONS

Ketanserin but not propranolol had a fully sedative profile and may confound pupillometric assessment of EDS. Beta adrenergic receptors do not appear to participate in arousal and pupillary functions, while 5HT1a receptors reduce pupil size without affecting arousal. Pupil size may not be used unequivocally as an index of the level of alertness in the case of drug-induced changes, when drugs interfere with the central pupil control mechanism in ways that are unrelated to their effects on arousal.

Larger tonic pupil size in young children with autism spectrum disorder

The symptoms of Autism Spectrum Disorder (ASD) have been suggested to manifest from atypical functioning of the autonomic nervous system (ANS), leading to altered arousal and atypical processing of salient stimuli. Coherent with this, persons with ASD show heightened autonomic activity, sleep difficulties, and structural and neurochemical alterations within the ANS. Recently, we observed decreased pupil responses to human faces in children with ASD. In the current study, we found differences in baseline (tonic) pupil size, with the ASD group exhibiting a larger pupil size than age-matched controls. Pupil responses are sensitive and reliable measures of ANS functioning, thus, this finding highlights the role of the ANS, and may provide clues about underlying neuropathology.

The 5-min pupillary alertness test is sensitive to modafinil: a placebo controlled study in patients with sleep apnea

RATIONALE

The extent of pupillary miosis during 5 min in darkness is a simple, recently introduced alertness test which may become useful in the clinical assessment of normal and pathological sleepiness.

OBJECTIVES

In this study, we further validated this test by testing its sensitivity to the effects of modafinil, a non-stimulant, alertness-promoting drug.

METHODS

Twelve unmedicated patients recently diagnosed with obstructive sleep apnea (OSA) after polysomnography, received placebo or modafinil (200 mg), according to a double-blind, cross-over design. The patients' resting pupil diameter (RPD) was sampled over 5 min in darkness before (10:00 A.M.) and after treatment (2:00 P.M.), and their light reflexes were elicited and recorded in darkness with an infrared video pupillometer.

RESULTS

We found a circadian miosis at 2:00 P.M. in the placebo treatment condition, which was reversed by modafinil. This effect correlated with modafinil-induced increase in subjective alertness, and it was greater in the most severely affected patients in terms of lowest oxygen saturation, independently of body mass index, age, or apneic episodes during sleep. Modafinil reduced the light reflex amplitude, suggesting an increase in the inhibitory input at the pupilloconstrictor Edinger-Westphal nucleus.

CONCLUSIONS

These effects of modafinil are best explained via an activation of the hypoxia-sensitive nucleus locus coeruleus. The 5-min pupillary alertness test has promising predictive validity, and it holds promise as a fast and sensitive method for the objective assessment of excessive daytime sleepiness, monitoring of disease progression, and response to treatment.

Arousal and the pupil: why diazepam-induced sedation is not accompanied by miosis

RATIONALE

There is a close relationship between arousal and pupil diameter, decrease in the level of arousal being accompanied by constriction of the pupil (miosis), probably reflecting the attenuation of sympathetic outflow as sedation sets in. Paradoxically, sedation induced by benzodiazepines is not accompanied by miosis.

OBJECTIVE

The objective of this study was to examine the hypothesis that diazepam may attenuate both the sympathetic and the opposing parasympathetic outflow to the iris, which may mask the miosis. Dapiprazole (sympatholytic) and tropicamide (parasympatholytic) were applied topically, together with the cold pressor test (CPT), to manipulate the sympathetic/parasympathetic balance.

MATERIALS AND METHODS

Sixteen healthy male volunteers participated in four weekly sessions according to a balanced double-blind protocol. Diazepam 10 mg (two sessions) and placebo (two sessions), associated with either 0.01% tropicamide or 0.5% dapiprazole eyedrops, were administered orally. Pupil diameter, light and darkness reflexes and pupillary sleepiness waves were recorded with infrared video pupillometry, alertness was measured by critical flicker fusion frequency (CFFF) and visual analogue scales (VAS), blood pressure and heart rate by conventional methods. CPT was applied after post-treatment testing. Data were analysed by analysis of variance, with multiple comparisons.

RESULTS

Diazepam caused sedation (reduction in VAS alertness scores and CFFF, increase in sleepiness waves), dapiprazole had a sympatholytic and tropicamide a parasympatholytic effect on the pupil. Diazepam had no effect on pupil diameter and reflexes or their modifications by the antagonists. CPT increased pupil diameter, blood pressure and heart rate, and the increase only in systolic blood pressure was attenuated by diazepam.

CONCLUSIONS

Diazepam-induced sedation is not accompanied by any change in either the sympathetic or parasympathetic influence on the iris.