Late onset obesity in mice with targeted deletion of potassium inward rectifier Kir7.1 from cells expressing the melanocortin-4 receptor.

Energy stores in fat tissue are determined in part by the activity of hypothalamic neurones expressing the melanocortin-4 receptor (MC4R). Even a partial reduction in MC4R expression levels in mice, rats or humans produces hyperphagia and morbid obesity. Thus, it is of great interest to understand the molecular basis of neuromodulation by the MC4R. The MC4R is a G protein-coupled receptor that signals efficiently through GαS , and this signalling pathway is essential for normal MC4R function in vivo. However, previous data from hypothalamic slice preparations indicated that activation of the MC4R depolarised neurones via G protein-independent regulation of the ion channel Kir7.1. In the present study, we show that deletion of Kcnj13 (ie, the gene encoding Kir7.1) specifically from MC4R neurones produced resistance to melanocortin peptide-induced depolarisation of MC4R paraventricular nucleus neurones in brain slices, resistance to the sustained anorexic effect of exogenously administered melanocortin peptides, late onset obesity, increased linear growth and glucose intolerance. Some MC4R-mediated phenotypes appeared intact, including Agouti-related peptide-induced stimulation of food intake and MC4R-mediated induction of peptide YY release from intestinal L cells. Thus, a subset of the consequences of MC4R signalling in vivo appears to be dependent on expression of the Kir7.1 channel in MC4R cells.

The effect of noise-cancelling headphones or music on pain perception and anxiety in men undergoing transrectal prostate biopsy.

OBJECTIVE: To assess the effect of noise-cancelling headphones with or without music on patient pain and anxiety associated with routine, office-based transrectal ultrasound (TRUS)-guided prostate biopsy in a prospective randomized study. METHODS: Patients scheduled for prostate biopsy as a result of elevated prostate-specific antigen and/or abnormal digital rectal examination were prospectively enrolled and randomized into a control, noise-cancelling headphones, or music-headphones group. Patients completed pain and anxiety questionnaires and had their physiological parameters assessed before and after the procedure and compared across groups. RESULTS: Eighty-eight patients were enrolled. Pain scores increased from baseline across all study groups, with the lowest mean score in the music group. No appreciable change was noted in anxiety scores after the procedure between groups (P>.05). Although postbiopsy systolic blood pressure values remained comparable with baseline levels in all groups, postbiopsy diastolic blood pressure increased in the control and headphones groups (P=.062 and .088, respectively) but remained stable in the music group (P=.552) after biopsy, indicating lesser physiological response to anxiety and pain in this group. CONCLUSION: Music-induced attention shift during prostate biopsy may have a beneficial impact on procedural anxiety and pain perception, but no apparent effect was noted for use of headphones alone. Further studies are necessary to explore strategies to reduce perceived anxiety and pain in men undergoing prostate biopsy.