Cholinergic modulation of dopaminergic reward areas: upstream and downstream targets of nicotine addiction

Nicotine reinforces smoking behaviour by activating nicotinic acetylcholine receptors in the midbrain dopaminergic reward centres. Upstream of the dopaminergic neurons nicotine induces long-term potentiation of the excitatory input to dopamine cells in the ventral tegmental area, and depresses inhibitory inputs. Both effects of nicotine were shown to last much longer than the nicotine exposure and together will activate the dopaminergic ventral tegmental area projection toward the nucleus accumbens. However, downstream of dopamine, effects of nicotine are also likely to occur. Cholinergic interneurons within the nucleus accumbens are important in the tonic control of the γ-amino buteric acid (GABA) nucleus accumbens output neurons, which project back to the ventral tegmental area. The nicotinic acetylcholine receptors that mediate this control are likely to desensitise upon preexposure to the nicotine concentrations found in the blood of smokers. Thus, synaptic mechanisms both upstream and downstream of dopamine release are potentially important factors contributing to the etiology of nicotine addiction.     

Quantification of local rectal wall displacements by virtual rectum unfolding.

BACKGROUND AND PURPOSE: To develop a method to project surface elements of a bent tubular organ, e.g. the rectum, in order to create a two-dimensional (2D) map and to use this method to quantify on a local scale shape and position variations of the rectum. PATIENTS AND METHODS: For this study we used data of 19 patients, who each received a planning CT scan and 9-13 repeat CT scans that were considered representative for the radiotherapy course. We combined maps from multiple CT scans of the same patient to quantify local rectal wall displacements. To make a map we first computed a central axis through the rectum and divided it into segments of equal length assuming that the length of these segments was invariant under rectum shape and position changes. Next, we constructed for each segment a planar cross section through the rectum, which was oriented orthogonally to that segment. The amount of rectal wall tissue was assumed to be constant in all orthogonal cross sections throughout the entire rectum. We unfolded the cross-sected rectal wall at the dorsal side and projected either the associated dose or the coordinates onto the map. RESULTS: The largest variation in the position of the rectal wall during the treatment course occurred at the upper anterior, left and right side (1 SD=5-7 mm). Near the anus the variation was <3 mm (1 SD) and at the posterior side of the rectum <4 mm (1 SD). The anterior-posterior (AP) and left-right displacements between the rectum in the planning CT scan and the mean rectum shape during the treatment were localized between 40 and 80% of the central axis. At the upper anterior, left, and right side the displacements were 5-8 mm (1 SD). These rectal wall displacements correlated with the rectum volume in the planning CT scan. At the upper anterior side the correlation coefficient between the AP displacements and the planning rectum volume was 0.85. CONCLUSIONS: We quantified variations in rectum shape and in dose in the rectal wall. The systematic error in rectal wall position was found to be larger than the random shape and position variations. We successfully developed a method to virtually unfold a rectum and to project the dose onto a 2D map. The spatial information of the dose distribution can be used in the analysis of rectum complications.     

Activation of the aryl hydrocarbon receptor is essential for mediating the anti-inflammatory effects of a novel low-molecular-weight compound

VAF347 is a low-molecular-weight compound that inhibits allergic lung inflammation in vivo. This effect is likely the result of a block of dendritic cell (DC) function to generate proinflammatory T-helper (Th) cells because VAF347 inhibits interleukin (IL)-6, CD86, and human leukocyte antigen (HLA)-DR expression by human monocyte-derived DC, 3 relevant molecules for Th-cell generation. Here we demonstrate that VAF347 interacts with the aryl hydrocarbon receptor (AhR) protein, resulting in activation of the AhR signaling pathway. Functional AhR is responsible for the biologic activity of VAF347 because (1) other AhR agonists display an identical activity profile in vitro, (2) gene silencing of wild-type AhR expression or forced overexpression of a trans-dominant negative AhR ablates VAF347 activity to inhibit cytokine induced IL-6 expression in a human monocytic cell line, and (3) AhR-deficient mice are resistant to the compound's ability to block allergic lung inflammation in vivo. These data identify the AhR protein as key molecular target of VAF347 and its essential role for mediating the anti-inflammatory effects of the compound in vitro and in vivo.     

A new automated method for rat sleep deprivation with minimal confounding effects on corticosterone and locomotor activity

The function of sleep in physiology, behaviour and cognition has become a primary focus of neuroscience. Its study inevitably includes experimental sleep deprivation designs. However, concerns exist regarding confounds like stress, increased locomotor activity levels, and decreased motivation to perform operant tasks induced by the methods employed. We here propose a novel procedure for sleep deprivation in rats and evaluate how it affects sleep, corticosterone concentration profiles, locomotor activity levels, and motivation to perform an operant task. Before, during and after 12h of total sleep deprivation by means of gradually increasing the rotation variability and the speed of a novel automated, two-compartment sleep deprivation device, sleep-wake states were assessed by electroencephalography (n=21), brain extracellular corticosterone concentrations using microdialysis (n=11), locomotor activity by infrared measurements (n=8), and operant performance using a fixed-interval-fixed-ratio task (n=16). Sleep was effectively prevented during the procedure; rats on average slept less than 1% of the time (0.8±0.2%, mean±standard error). Brain corticosterone concentrations were mildly increased during the procedure, but did not exceed normal peak concentrations. Locomotor activity was not only increased during the procedure, but also did not exceed the peak levels found during undisturbed wakefulness. Food restriction to 12 g/rat/day prevented sleep deprivation from reducing the motivation to perform an operant task. This novel procedure can be applied to sleep deprive rats in a highly effective way, while keeping corticosterone and locomotor activity within the normal range.     

A validated liquid chromatography-tandem mass spectrometry method for the quantitative determination of 4β-hydroxycholesterol in human plasma

A novel liquid chromatography-tandem mass spectrometry method is described for the quantitative determination of the endogenous CYP 3A4/5 marker 4β-hydroxycholesterol in human K(2)-EDTA plasma. It is based on alkaline hydrolysis to convert esterified to free 4β-hydroxycholesterol, followed by analyte extraction from plasma by hexane and purification of the hexane extract by normal-phase solid-phase extraction. The analyte is chromatographically separated from endogenous isobaric plasma oxysterols and excess cholesterol by a 16-min reversed-phase gradient on a C18 column; detection is performed by atmospheric pressure photoionization tandem mass spectrometry in the positive ion mode, using toluene as a dopant. Using 400μl of plasma, 4β-hydroxycholesterol can be quantified in the concentration range 10.0-250nM. Validation results show that the method is sufficiently selective towards endogenous plasma sterols and capable of quantifying the analyte with good precision and accuracy. The analyte is sufficiently stable in all relevant matrices and solvents; the addition of the anti-oxidant butylated hydroxytoluene to prevent in vitro formation of 4β-hydroxycholesterol from cholesterol during storage or analysis is not necessary, provided that long-term frozen storage of plasma occurs at -70°C.     

Effects of intraoperative breaks on mental and somatic operator fatigue: a randomized clinical trial

Background  

Intermittent work breaks are common in fields with high workload but not yet for surgeons during operations. We evaluated the effects of intraoperative breaks during complex laparoscopic surgery (5 min every half hour) on the surgeon.