Psychological and neuroendocrine responses to social stress and to the administration of the alpha-2-receptor antagonist, yohimbine, in highly trained endurance athletes in comparison to untrained healthy controls.

INTRODUCTION: Several clinical studies suggest antidepressive and anxiolytic effects of regular endurance training. The mechanisms by which exercise exerts these effects are still unclear. It was hypothesized that athletes might show a diminished reaction to psychosocial stress and noradrenergic stimulation. METHODS: 12 male athletes and 12 healthy untrained male controls underwent a challenge paradigm on 3 separate days: the alpha-2-receptor antagonist yohimbine (0.4 mg/kg), placebo or a psychosocial stress test (SST) were administered. Responses were measured by psychometric scales, plasma cortisol, blood pressure and heart rate. RESULTS: Before testing, psychometric variables and cortisol levels were not different between the 2 groups. In comparison to placebo conditions, both the social stress test and the administration of yohimbine were followed by significant increases of anxiety symptoms, plasma cortisol, heart rate and blood pressure in both groups. However, these responses were not significantly different between the group of athletes and the control group. DISCUSSION: These results do not support the hypotheses that high aerobic fitness is associated with attenuated psychological and neuroendocrine responses to yohimbine or to psychosocial stress.

Amphipols from A to Z.

Amphipols (APols) are short amphipathic polymers that can substitute for detergents to keep integral membrane proteins (MPs) water soluble. In this review, we discuss their structure and solution behavior; the way they associate with MPs; and the structure, dynamics, and solution properties of the resulting complexes. All MPs tested to date form water-soluble complexes with APols, and their biochemical stability is in general greatly improved compared with MPs in detergent solutions. The functionality and ligand-binding properties of APol-trapped MPs are reviewed, and the mechanisms by which APols stabilize MPs are discussed. Applications of APols include MP folding and cell-free synthesis, structural studies by NMR, electron microscopy and X-ray diffraction, APol-mediated immobilization of MPs onto solid supports, proteomics, delivery of MPs to preexisting membranes, and vaccine formulation.