Functional influence of the central noradrenergic system on the skin conductance activity in rats

Diurnal Emotional States Impact the Sleep Course

BACKGROUND

Diurnal emotional experiences seem to affect several characteristics of sleep architecture. However, this influence remains unclear, especially for positive emotions. In addition, electrodermal activity (EDA), a sympathetic robust indicator of emotional arousal, differs depending on the sleep stage. The present research has a double aim: to identify the specific effects of pre-sleep emotional states on the architecture of the subsequent sleep period; to relate such states to the sympathetic activation during the same sleep period.

METHODS

Twelve healthy volunteers (20.1 ± 1.0 yo.) participated in the experiment and each one slept 9 nights at the laboratory, divided into 3 sessions, one per week. Each session was organized over three nights. A reference night, allowing baseline pre-sleep and sleep recordings, preceded an experimental night before which participants watched a negative, neutral, or positive movie. The third and last night was devoted to analyzing the potential recovery or persistence of emotional effects induced before the experimental night. Standard polysomnography and EDA were recorded during all the nights.

RESULTS

Firstly, we found that experimental pre-sleep emotional induction increased the Rapid Eye Movement (REM) sleep rate following both negative and positive movies. While this increase was spread over the whole night for positive induction, it was limited to the second half of the sleep period for negative induction. Secondly, the valence of the pre-sleep movie also impacted the sympathetic activation during Non-REM stage 3 sleep, which increased after negative induction and decreased after positive induction.

CONCLUSION

Pre-sleep controlled emotional states impacted the subsequent REM sleep rate and modulated the sympathetic activity during the sleep period. The outcomes of this study offer interesting perspectives related to the effect of diurnal emotional influences on sleep regulation and open new avenues for potential practices designed to alleviate sleep disturbances.

The anatomical and functional relationship between the P3 and autonomic components of the orienting response

Many psychophysiologists have noted the striking similarities between the antecedent conditions for the P3 component of the event-related potential and the orienting response: both are typically elicited by salient, unexpected, novel, task-relevant, and other motivationally significant stimuli. Although the close coupling of the P3 and orienting response has been well documented, the neural basis and functional role of this relationship is still poorly understood. Here we propose that the simultaneous occurrence of the P3 and autonomic components of the orienting response reflects the co-activation of the locus coeruleus-norepinephrine system and the peripheral sympathetic nervous system by their common major afferent: the rostral ventrolateral medulla, a key sympathoexcitatory region. A comparison of the functional significance of the locus coeruleus-norepinephrine system and the peripheral sympathetic nervous system suggests that the P3 and orienting response reflect complementary cognitive and physical contributions to the mobilization for action following motivationally significant stimuli.

Psychiatric symptoms of noradrenergic dysfunction: a pathophysiological view

What psychiatric symptoms are caused by central noradrenergic dysfunction? The hypothesis considered in this review is that noradrenergic dysfunction causes the abnormalities in arousal level observed in functional psychoses. In this review, the psychiatric symptoms of noradrenergic dysfunction were inferred pathophysiologically from the neuroscience literature. This inference was examined based on the literature on the biology of psychiatric disorders and psychotropics. Additionally, hypotheses were generated as to the cause of the noradrenergic dysfunction. The central noradrenaline system, like the peripheral system, mediates the alarm reaction during stress. Overactivity of the system increases the arousal level and amplifies the emotional reaction to stress, which could manifest as a cluster of symptoms, such as insomnia, anxiety, irritability, emotional instability and exaggerated fear or aggressiveness (hyperarousal symptoms). Underactivity of the system lowers the arousal level and attenuates the alarm reaction, which could result in hypersomnia and insensitivity to stress (hypoarousal symptoms). Clinical data support the hypothesis that, in functional psychoses, the noradrenergic dysfunction is in fact associated with the arousal symptoms described above. The anti-noradrenergic action of anxiolytics and antipsychotics can explain their sedative effects on the hyperarousal symptoms of these disorders. The results of animal experiments suggest that excessive stress can be a cause of long-term noradrenergic dysfunction.

The dose-dependent effect of methylphenidate on performance, cognition and psychophysiology

The effects of methylphenidate (MPH) on 32 healthy human male volunteers (aged 18 to 25 years, mean age=22.26) were examined using a within-subject design. Each participant attended six testing periods, held once per week. Within each testing period, three repeat testing sessions were undertaken: pre-medication, on-medication and two hours post-medication. In these sessions, dose was manipulated (placebo, 5 mg, 15 mg or 45 mg) according a double-blind placebo design. In this report, we focus on behavioral, autonomic arousal (heart rate, skin conductance) and psychophysiological (ERP) data acquired during the working memory task. We found increased autonomic arousal (heart rate, skin conductance and blood pressure) with MPH. A linear reduction in reaction time, omission errors and target P3 latency, and a corresponding increase in background P3 amplitude was observed with increased MPH dose. The relationship between these measures supported an increase in performance and underlying brain function with MPH. To our knowledge, this is the first paper to use behavioral, arousal and electrophysiological measures in an integrative approach to study the effects of MPH on healthy adults.

Decrement of the skin conductance response to repeated volitional inspiration

OBJECTIVE

To examine response decrement of the recently reported inspiratory skin conductance response (SCR) [Lim CL, Seto-Poon M, Clouston PD, Morris JG. Sudomotor nerve conduction velocity and central processing time of the skin conductance response. Clin Neurophysiol 2003;114:2172-80].

METHODS

Twelve healthy adult volunteers performed 3 tasks (A) a control task of maintaining tidal breathing and then two randomized tasks, (B) a deep inspiration to a target oral pressure and (C) tapping with a finger. Each task was performed 30 times on cue every 20s in 3 runs with 5 min of rest between runs. The SCR, oral pressure, airflow, inspired volume and cue signal were recorded continuously and analysed offline. SCR amplitude was logarithmically transformed and then statistically analysed, using a linear mixed effects model, as a function of run number, trial number and absolute error between target and actual oral pressures.

RESULTS

Inspiratory efforts elicited exponentially decreasing SCR amplitude with increasing trial number during each run (P < 0.0001). After adjusting for trial number, the mean SCR amplitude of the second and the third run were, respectively, 24.2 (95% CI (0.175, 0.336), P < 0.001) and 14.4% (95% CI (0.104, 0.200), P < 0.001) of the first run amplitude.

CONCLUSIONS

Volitional deep inspiration reliably activates an SCR that exhibits response decrement with repetition, which may be habituation.

SIGNIFICANCE

The volitional inspiratory SCR may assist in the assessment of sympathetic autonomic status in patients with peripheral afferent neuropathy.

Proposal for a noradrenaline hypothesis of schizophrenia

In this article, we have reevaluated the role of noradrenergic dysfunction in the pathogenesis of schizophrenia in the light of today's neuroscience and clinical data. Neurophysiological, psychophysiological, psychopharmacological, and biochemical findings that have accumulated in last decades indicate that certain noradrenergic dysfunctions play important roles in the pathogenesis of the disorder. Moreover, these findings provide us with consistent evidence for the existence of two syndromes generated by either overactivity or underactivity of the central noradrenaline (NA) system. The former appears to correspond to the type I syndrome (positive symptoms) and the latter to the type II syndrome (negative symptoms). We conclude that the involvement of brain NA in cerebral metabolism and blood flow as well as the amine's role in brain development and neuronal differentiation may provide the mechanisms underlying the disease process in schizophrenia. Development of chemical agents acting specifically on the brain noradrenergic mechanisms may be a promising approach to novel treatments of the disorder.

Ephedrine, but not phenylephrine, increases bispectral index values during combined general and epidural anesthesia

Ephedrine and phenylephrine are used to treat hypotension during combined general and epidural anesthesia, and they may change anesthetic depth. In the current study, we evaluated the effects of ephedrine versus phenylephrine on bispectral index (BIS) during combined general and epidural anesthesia. After injection of ropivacaine through the epidural catheter, general anesthesia was induced with propofol and vecuronium, and was maintained with 0.75% sevoflurane. Approximately 10 min after the intubation, BIS was recorded as a baseline value. Patients with decreases in arterial blood pressure <30% of the preanesthetic values were defined as control group (n = 9). Patients who had to be treated for larger decreases in arterial blood pressure were randomly assigned to receive ephedrine 0.1 mg/kg (n = 17) or phenylephrine 2 micro g/kg (n = 17). BIS values were recorded at 1-min intervals for 10 min. BIS in the ephedrine group was significantly larger from 7 to 10 min than that in the control and phenylephrine groups (P < 0.05). Seven patients in the ephedrine group had BIS >60, whereas no patient in the control and phenylephrine groups had BIS >60 (P < 0.005). Ephedrine, but not phenylephrine, increased BIS during general anesthesia combined with epidural anesthesia.

Autonomic activity in relation to cerebrospinal fluid neurochemistry in obsessive and disruptive children and adolescents

Electrodermal activity and heart rate were recorded during rest, simple tones, and a reaction time task in 43 male and female adolescents and children with obsessive compulsive disorder and 30 male adolescents and children with disruptive behavior disorders who had lumbar cerebrospinal fluid drawn during the same week. Partial correlations controlling for age and sex showed that in the obsessive group metabolites of serotonin and dopamine, but not of norepinephrine, were positively correlated with electrodermal responsivity, most consistently in the reaction time task. This result was not replicated in disruptive boys. Adrenocorticotropic hormone was positively related to electrodermal activity and heart rate throughout the session. The results for the obsessive adolescents suggest that nigrostriatal dopamine turnover and central serotonin turnover affect electrodermal activity, generally confirming and extending conclusions from pharmacological studies. Diagnosis may affect these relationships.

Possible noradrenergic dysfunction in schizophrenia

In spite of extensive studies over the last 2 decades to find direct evidence in support of the dopamine hypothesis of schizophrenia, no undisputed experimental data has been obtained. In contrast, estimation of noradrenalin (another major catecholamine) and its metabolites in postmortem brain and in the cerebrospinal fluid appears to be producing consistent results. To understand the meaning of this change for the pathogenesis of the illness, we have carried out animal experiments in which reproducibility of schizophrenic signs and symptoms by noradrenergic dysfunction, and treatability of the disorder by modulation of noradrenergic activity were studied. First, psychophysiological signs in skin conductance responsiveness (nonhabituating or nonresponding change) and smooth pursuit eye movement (spiky or stepwise pursuit) could be reproduced by enhancing or suppressing central noradrenergic activity. Behavioral abnormalities resembling schizophrenic symptoms are known to be reproducible by over- or underactivity of the system (overarousal or underarousal syndrome). Secondly, the action of various drugs capable of modulating schizophrenic symptoms was analyzed in relation to noradrenergic activity. Haloperidol, in particular, had a potent suppressing effect on skin conductance activity (spontaneous fluctuation rate and habituation rate) when administered chronically, suggesting its inhibitory action on noradrenergic activity.