Preemptive Caffeine Administration Blocks the Increase in Postoperative Pain Caused by Previous Sleep Loss in the Rat: A Potential Role for Preoptic Adenosine A2A Receptors in Sleep-Pain Interactions.

Sleep and pain are reciprocally related, but the precise mechanisms underlying this relationship are poorly understood. This study used a rat model of surgical pain to examine the effect of previous sleep loss on postoperative pain and tested the hypothesis that preoptic adenosinergic mechanisms regulate sleep-pain interactions. Relative to ad libitum sleep, 6 hours of total sleep deprivation prior to a surgical incision significantly enhanced postoperative mechanical hypersensitivity in the affected paw and prolonged the time to recovery from surgery. There were no sex-specific differences in these measures. There were also no changes in adrenocorticotropic hormone and corticosterone levels after sleep deprivation, suggesting that this effect was not mediated by the stress associated with the sleep perturbation. Systemic administration of the nonselective adenosine receptor antagonist caffeine at the onset of sleep deprivation prevented the sleep deprivation-induced increase in postoperative hypersensitivity. Microinjection of the adenosine A2A receptor antagonist ZM 241385 into the median preoptic nucleus (MnPO) blocked the increase in surgical pain levels and duration caused by prior sleep deprivation and eliminated the thermal hyperalgesia induced by sleep deprivation in a group of nonoperated (i.e., without surgical incision) rats. These data show that even a brief sleep disturbance prior to surgery worsens postoperative pain and are consistent with our hypothesis that adenosine A2A receptors in the MnPO contribute to regulate these sleep-pain interactions.

A test of different menu labeling presentations.

Chain restaurants will soon need to disclose calorie information on menus, but research on the impact of calorie labels on food choices is mixed. This study tested whether calorie information presented in different formats influenced calories ordered and perceived restaurant healthfulness. Participants in an online survey were randomly assigned to a menu with either (1) no calorie labels (No Calories); (2) calorie labels (Calories); (3) calorie labels ordered from low to high calories (Rank-Ordered Calories); or (4) calorie labels ordered from low to high calories that also had red/green circles indicating higher and lower calorie choices (Colored Calories). Participants ordered items for dinner, estimated calories ordered, and rated restaurant healthfulness. Participants in the Rank-Ordered Calories condition and those in the Colored Calories condition ordered fewer calories than the No Calories group. There was no significant difference in calories ordered between the Calories and No Calories groups. Participants in each calorie label condition were significantly more accurate in estimating calories ordered compared to the No Calories group. Those in the Colored Calories group perceived the restaurant as healthier. The results suggest that presenting calorie information in the modified Rank-Ordered or Colored Calories formats may increase menu labeling effectiveness.