[Psychophysiology of visceral pain]. / Psychophysiologische Grundlagen viszeraler Schmerzen.

The psychophysiology of visceral pain is--different from cardiac psychophysiology--much less well investigated due to the invasiveness of its methods and problems associated with reliably and reproducibly stimulating as well as recording of the gastrointestinal tract. Despite these problems, the last 30 years have documented a number of psychophysiological phenomena such as the perception (interoception) of visceral stimuli, the effect of emotions and stress on visceral sensations, and the effect of visceral processes on cortical processing. This was mainly due to the application of neurophysiological techniques (cortical imaging and stimulation) in these investigations.

Perception and pain thresholds for cutaneous heat and cold, and rectal distension: associations and disassociations.

BACKGROUND: Hypersensitivity to somatic or visceral pain has been reported in numerous clinical conditions such as fibromyalgia or the irritable bowel syndrome, and general hypersensitivity has been proposed to be the underlying mechanism. However, cross-modal relationships especially between somatic and visceral pain have rarely been investigated even in healthy volunteers. Furthermore, psychological influences on pain have rarely been characterized across modalities. METHODS: Sixty-one healthy participants underwent testing of perception and pain thresholds for cutaneous thermode heat and cold, as well as for rectal balloon distension. Psychological testing for anxiety, depression, and pain experience (including catastrophizing and coping) as well as cardiac interoception was performed. Measurement quality and the correlations between the different modalities were examined. KEY RESULTS: Significant correlations existed between the perception thresholds for cold/heat (τB  = -0.28, p = 0.002) and cold/distension (τB  = -0.21, p = 0.03) and for the pain thresholds for cold/heat (r = -0.61, p < 0.001) and heat/distension (r = 0.33, p = 0.01). No association was found between pain thresholds and anxiety, depression, psychological experience with and processing of pain, or cardiac interoception. Retest reliabilities for pain measurements were satisfying after short intertrial intervals (all intraclass correlation coefficients >0.8), but less so after longer intervals. The individuals contributing to the respective correlations differ between measurements. CONCLUSIONS & INFERENCES: Moderate associations were found for pain thresholds across modalities. The strength of the associations and their stability over time warrants further investigation and might serve to increase the understanding of conditions affecting multiple pain modalities.

[Placebo response: in studies on pain and under other clinical conditions]. / Placeboresponse: In Studien zum Schmerz und anderen klinischen Bedingungen.

This contribution compares unexplained essential questions regarding the placebo response with current empirical evidence: (1) Are the placebo response rates equivalent in the groups treated with medication or placebo? Very little evidence has been gathered to support this generally accepted additivity while some findings negate its validity. (2) Is the placebo response a function of the probability of receiving medication or placebo? There are indications that the number of study groups included in a trial determines the level of placebo and medication response. (3) How great is the placebo response in trials that directly compare a (new) medication with one that for example is already on the market? There are indications that such comparative studies produce higher placebo response rates. (4) How high is the placebo response rate in everyday clinical practice--or does the response to a medication in trials substantiate the effect of the medication in everyday clinical practice?

In vivo short-term and long-term host reaction to starch-based scaffolds.

The implantation of biomaterials may elicit a host response to this foreign body, and the magnitude of that reaction depends on the host and on the implanted material. The aim of this study was to compare the inflammatory response induced by the implantation of starch-based (SPCL) scaffolds in two implantation rat models: subcutaneous (SC) and intramuscular (IM). Moreover, two methodologies, wet spinning (WS) and fibre-bonding (FB), were used to prepare the scaffolds. The short-term inflammatory/immune host reaction was assessed by SC and IM implantations in rats after 1 and 2 weeks, and the long-term host response was addressed after 8 and 12 weeks of SC implantation of both types of SPCL scaffolds in rats. After each time period, the scaffolds, surrounding tissue and nearby lymph nodes were explanted, and used for histological analysis and molecular biology evaluation. The results showed that SPCL-WS scaffolds seem to induce a slight lower inflammatory/immune reaction in both types of implantation models. Nonetheless, comparing the two models, the IM implantation resulted in a slightly higher inflammatory response than the SC implantation with early activation of the lymph nodes. The overall data suggests a good integration of the materials in the host, independently of the tissue location with a normal progress of the reaction for all the conditions.