Increased pupillary sensitivity to pilocarpine in depression

Cholinergic regulation of mood: from basic and clinical studies to emerging therapeutics

Mood disorders are highly prevalent and are the leading cause of disability worldwide. The neurobiological mechanisms underlying depression remain poorly understood, although theories regarding dysfunction within various neurotransmitter systems have been postulated. Over 50 years ago, clinical studies suggested that increases in central acetylcholine could lead to depressed mood. Evidence has continued to accumulate suggesting that the cholinergic system has a important role in mood regulation. In particular, the finding that the antimuscarinic agent, scopolamine, exerts fast-onset and sustained antidepressant effects in depressed humans has led to a renewal of interest in the cholinergic system as an important player in the neurochemistry of major depression and bipolar disorder. Here, we synthesize current knowledge regarding the modulation of mood by the central cholinergic system, drawing upon studies from human postmortem brain, neuroimaging, and drug challenge investigations, as well as animal model studies. First, we describe an illustrative series of early discoveries which suggest a role for acetylcholine in the pathophysiology of mood disorders. Then, we discuss more recent studies conducted in humans and/or animals which have identified roles for both acetylcholinergic muscarinic and nicotinic receptors in different mood states, and as targets for novel therapies.

Pupillometric Characteristics in Patients with Choroidal Neovascularization Due to Age-Related Macular Degeneration

Purpose

To study the pupillary light reflex in patients with choroidal neovascularization due to age-related macular degeneration (AMD).

Methods

The study included 15 patients with AMD and 15 control subjects. A full recording of the pupil's reaction to light was registered and the following eight parameters were measured and reported: baseline pupil radius (R1), latency (T1), minimum pupil radius (R2), amplitude (AMP), maximum constriction velocity (VCmax), maximum constriction acceleration (AC-max), time for maximum velocity (T2), and time for maximum constriction (T3).

Results

All variables measured presented alterations in the AMD group and a number of them were significantly reduced in the AMD group.

Conclusions

The presence of neovascular AMD significantly affects the pupil's response to light stimulus when compared to normal subjects.

Visual system manifestations of Alzheimer's disease

Alzheimer's disease (AD) is an increasingly common disease with massive personal and economic costs. While it has long been known that AD impacts the visual system, there has recently been an increased focus on understanding both pathophysiological mechanisms that may be shared between the eye and brain and how related biomarkers could be useful for AD diagnosis. Here, were review pertinent cellular and molecular mechanisms of AD pathophysiology, the presence of AD pathology in the visual system, associated functional changes, and potential development of diagnostic tools based on the visual system. Additionally, we discuss links between AD and visual disorders, including possible pathophysiological mechanisms and their relevance for improving our understanding of AD.

Pupillometry in Chinese female patients with depression: a pilot study

The pupillary responses to light in patients with depression and normal controls were evaluated among Chinese females. Four parameters related to the pupil were assessed using a video-based pupillometer. The results showed that there were significant differences in the pupil area in the darkness and the pupil area at the peak of constriction between depressed patients and normal controls.

Cholinergic sensitivity predicts severity of mania

Our laboratory and others have reported that pupillary constrictions following application of the cholinergic agonist pilocarpine are increased in depressed patients. Moreover, mood improvements in manic patients, given lithium or Depakote, are also correlated with increases in pupil sensitivity. The present report describes the relationship between symptom severity and cholinergic sensitivity in a larger group (N=20) of manic patients (bipolar I; 296.4x). Pupil responses to pilocarpine eye drops (0-2%) were recorded using infrared pupillometry. The results were compared with pupil sizes measured under conditions of cholinergic blockade (0.5% tropicamide). Pupil responses were computed as percentages of the maximal range of areas measured under saturating agonist and antagonist conditions. Dose response curves were subjected to a log-logit transformation and ED(50) values were determined by weighted least squares regression. Bech-Rafaelsen mania ratings were found to be linearly related to ED(50) values (r=0.48). Patients with more severe mania required higher concentrations of pilocarpine in order to elicit a 50% reduction in pupil size. The present findings support a putative cholinergic role in the regulation of mood state. Moreover, the results suggest that pupillary responses may provide a simple and non-invasive means to evaluate cholinergic sensitivity in patients with affective disorders.

Automated standardized pupillometry with optical method for purposes of clinical practice and research

The aim of the current study was the introduction and standardization of two experimental conditions for dynamic pupillometry. Pupillometry is a method that can provide valuable data concerning the functioning of the autonomous nervous system. The system for recording the pupil reaction was developed in the Laboratory of Clinical Neurophysiology of the 1st Department of Neurology of Aristotle University of Thessaloniki, in co-operation with the Laboratory of Fluid Mechanics of the Aristotle University of Thessaloniki. This system is fully automated. It includes an infra-red video camera, which has the capacity to record in complete darkness, and an SLE (clinical photic stimulator) lamp. A software application automatically performed all the procedures. During the first experiment, one flash was administered. During the second experiment, a series of 25 flashes (1 Hz frequency) was administered. Fifty physically and mentally healthy subjects aged 23-48 years took part in the study. Means, standard deviations and ranges for all variables characterizing normal subjects during both experimental conditions are reported. Test/re-test results and comparisons of the two eyes are also reported. The combined use of these two experimental conditions in dynamic pupillometry may be a very useful tool in medical research. There are already reports on the usefulness of pupillometry in the research of various diseases, including depression and Alzheimer's disease. It is expected that it will also be a valuable research tool in the study of diabetes, alcoholism, myasthenia gravis, cancer, multiple sclerosis, etc.

Decreases in dilated pupil size in depressed patients with age may reflect adrenergic changes

Some studies have suggested that noradrenergic activity may decrease with age in depressed patients. Pupil size is regulated by a balance between norepinephrine and acetylcholine. The present study compares pupil size in 10 unmedicated patients with unipolar depression (296. 3) and in 16 normal controls. Pupil size after dilation with tropicamide, a cholinergic antagonist, was inversely related to age in the patients (r=-0.87), but did not diminish with age in controls. The results suggest that pupil size may provide an index of diminished noradrenergic function with age in patients with major depression.

Changes in pupil reaction to light in Alzheimer's disease patients: a preliminary report

The aim of this preliminary study was to compare the pupil reaction to light in Alzheimer's disease (AD) patients before and after treatment and in normal controls. Ten AD patients diagnosed according to DSM-IV and NINCDS-ADRDA criteria (five medication-free and five under anticholinesterase treatment) and five age- and gender-matched controls took part in the study. Drug-free patients and all control subjects were free of any medication for at least four weeks. An optical method was used to assess the pupil reaction to a single flash. Medication-free AD patients manifested shorter latency and lower amplitude of maximum response to light in comparison to controls. These findings are in agreement with the presence of a cholinergic deficit in AD patients. Pharmacological treatment with donepezil, which is an anticholinesterase agent partially improves this deficit. The results of this preliminary investigation suggest that dynamic pupillometry could be a useful adjunct to assist the diagnosis of early AD, and the differential diagnosis between different types of dementia. AD patients seem to manifest a specific pattern of pupil reaction to light, and some characteristics of this pattern are detectable even in patients receiving anticholinesterase medication. However, this is only a preliminary report and further research is mandatory.

Photopic and scotopic light detection in patients with seasonal affective disorder and control subjects

BACKGROUND

Retinal sensitivity may play a role in the pathogenesis of seasonal affective disorder (SAD) and response to light therapy.

METHODS

Using a dark adaptation procedure, SAD patients and normal control subjects were tested in the winter and summer, with patients retested after light treatment. The eyes were preadapted to bright light followed by 30 min in darkness, during which subjects detected a dim signal titrated around the detection threshold. Photopic (cone-mediated) and scotopic (rod-mediated) components of the data were identified by nonlinear exponential curve fits to successive threshold estimates.

RESULTS

Patients (n = 24) showed significantly lower cone and rod thresholds in the summer than winter, while control subjects (n = 12) showed a similar trend. Relative to the control subjects, however, patients were supersensitive in winter (lower cone final threshold, faster rod recovery). Clinical responders to morning light showed a small summer-like increase in cone sensitivity, whereas nonresponders became subsensitive. In comparison to darker-eyed patients, blue-eyed patients showed a larger summertime increase in cone sensitivity and a similar trend after response to morning light.

CONCLUSIONS

Heightened retinal sensitivity with increased light exposure, and supersensitivity of patients relative to control subjects in winter, may play roles in the pathogenesis of winter depression and the action of therapeutic light.

Sodium valproate increases pupillary responsiveness to a cholinergic agonist in responders with mania

BACKGROUND

The cholinergic hypothesis of affective disorders predicts that mania is a hypocholinergic state relative to monoaminergic activity. Treatments that increase cholinergic sensitivity are expected to improve manic symptoms. Valproic acid is an effective treatment for mania. Little, however, is known about the cholinergic effects of this agent.

METHODS

Ten male hypomanic or manic patients were treated with valproic acid (1500-2000 mg) for 2 weeks. Cholinergic sensitivity was assessed before, and after treatment using graded concentrations of pilocarpine eyedrops (0.03-2.0%). Pupil size changes were quantified using an infrared pupillometer and ED50 values were referenced to maximal dilation with 0.5% tropicamide.

RESULTS

Valproate treatment decreased Bech mania ratings and ED50 values (p < .0001). Improvements in mania after treatment were closely correlated with decreases in ED50 (r = .76; p < .01). This relationship was indistinguishable from one previously observed after lithium treatment.

CONCLUSIONS

These results provide support for the cholinergic-adrenergic hypothesis. Moreover, similar pupillary reactions to valproic acid and lithium treatments suggest that these agents may share a common action on muscarinic receptors.

Pupillary cholinergic sensitivity to pilocarpine increases in manic lithium responders

BACKGROUND

The cholinergic hypothesis of affective disorders predicts that mania is a hypocholinergic state relative to monoaminergic activity. Treatments that increase cholinergic sensitivity are expected to improve manic symptoms.

METHODS

Ten male hypomanic or manic patients were treated with lithium carbonate (0.7-1.1 mEq/L) for 2 weeks. Cholinergic sensitivity was assessed prior to, and following treatments, using graded concentrations of pilocarpine eyedrops (.03-2.0%). Pupil size changes were quantified using an infrared pupillometer and ED50 values were referenced to maximal dilation with .5% tropicamide.

RESULTS

Lithium treatment decreased Bech mania ratings and ED50 values (p < .001). Improvements in mania with lithium treatment were closely correlated with decreases in ED50 (r = .88, p < .001).

CONCLUSIONS

These results support the cholinergic-adrenergic hypothesis and suggest that one possible mechanism for the antimanic effects of lithium may involve increasing cholinergic activity in relation to monoaminergic neurotransmission.

Changes in pupil reaction to light in melancholic patients

The aim of the current study was to compare the pupil reaction to light in depressed patients and normal control subjects. Seven depressed patients with melancholic features according to DSM-IV criteria and 14 age- and gender-matched control subjects took part in the study. All were free of any medication for at least 2 weeks. All were aged between 25 and 50 years. An optical method was used to assess the pupil reaction to a single flash. Depressed patients manifested shorter latency for constriction than control subjects, and a marginal difference in the total work produced by acetylcholine. The results of the current study support the theory that there is a norepinephrine hypoactivity in melancholic depression, with less affected acetylcholine activity.