Lack of plasmic beta-endorphin response to a gastronomic meal in healthy humans

Antinociceptive effect of intermittent fasting via the orexin pathway on formalin-induced acute pain in mice

It has been suggested that stress responses induced by fasting have analgesic effects on nociception by elevating the levels of stress-related hormones, while there is limited understanding of pain control mechanisms. Here, we investigated whether acute or intermittent fasting alleviates formalin-induced pain in mice and whether spinal orexin A (OXA) plays a role in this process. 6, 12, or 24 h acute fasting (AF) and 12 or 24 h intermittent fasting (IF) decreased the second phase of pain after intraplantar formalin administration. There was no difference in walking time in the rota-rod test and distance traveld in the open field test in all groups. Plasma corticosterone level and immobility time in the forced swim test were increased after 12 h AF, but not after 12 h IF. 12 h AF and IF increased not only the activation of OXA neurons in the lateral hypothalamus but also the expression of OXA in the lateral hypothalamus and spinal cord. Blockade of spinal orexin 1 receptor with SB334867 restored formalin-induced pain and spinal c-Fos immunoreactivity that were decreased after 12 h IF. These results suggest that 12 h IF produces antinociceptive effects on formalin-induced pain not by corticosterone elevation but by OXA-mediated pathway.

Opioid peptides and the control of human ingestive behaviour

A variety of evidence suggests that endogenous opioid peptides play a role in the short-term control of eating. More recently, opioid receptor antagonists like naltrexone have been approved as a treatment for alcohol dependence. Here we review the evidence for a role of opioid peptides in both normal and abnormal eating and drinking behaviours and in particular try to identify the nature of the role of opioids in these behaviours. Particular attention is paid to the idea that opioid reward processes may be involved both in the short-term control of eating and hedonic aspects of alcohol consumption, and parallels are drawn between the effects of opiate antagonists on food pleasantness and the experience of drinking alcohol. The review also explores the extent to which data from studies using opiate antagonists and agonists provide evidence for a direct role of endogenous opioids in the control of ingestive behaviour, or alternatively whether these data may be better explained through non-specific effects such as the nausea commonly reported following administration of opiate antagonists. The review concludes that the present data suggests a single opioid mechanism is unlikely to explain all aspects of ingestive behaviour, but also concludes that opioid-mediated reward mechanisms play an important control in hedonic aspects of ingestion. The review also highlights the need for further empirical work in order to elucidate further the role of opioid peptides in human ingestive behaviour.

Functional food science and behaviour and psychological functions

The impact of ingesting various foods on psychological and behavioural functions is a topic of both interest and concern to the general public. In this article, the scientific literature concerning demonstrated cause-and-effect relationships is reviewed, beginning with methodological considerations specific to the quantification of particular behaviours and psychological events. The essential function of food is to satisfy hunger and the need for essential nutrients. The contributions of macronutrients to appetite and satiety are described, as well as their impact on metabolism and energy balance. Functional properties of macronutrient substitutes (high-intensity sweeteners, fat replacers) and flavour enhancers are examined in relation to their contribution to hunger, satiety, and energy balance. The effects of foods and individual nutrients on the performance of diverse psychomotor tasks are studied with consideration given to the various validated quantitative tools used to assess behaviour. The effects of food components on activation, sedation, and affective states such as dysphoria are also reviewed, with special attention given to brain function and neuroactive substances such as serotonin and the endorphins. The case of hyperactivity in children is given special emphasis with reference to the potential influence of sugar and food additives. Safety issues related to food constituents and additives are discussed. Finally, a set of criteria is proposed for the evaluation and elaboration of studies in the behavioural and psychological fields, along with suggestions for future research.

Endogenous opiates: 1991

This paper is the fourteenth installment of our annual review of research concerning the opiate system. It includes papers published during 1991 involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.

Immunoreactive beta-endorphin increases after an aspartame chocolate drink in healthy human subjects

It has been claimed that sucrose intake induces a rise in beta-endorphins. In an attempt to discriminate between the sensorial and metabolic effects of sucrose intake in this process, the effects of two chocolate drinks were compared: one sweetened with 50 g of sucrose, the other with 80 mg of aspartame. Plasma beta-endorphin concentrations were more elevated after the aspartame drink than after sucrose or fasting, while insulin increased after drinking as much with aspartame as with sucrose. We suggest that the increase in beta-endorphin after aspartame edulcorated chocolate is related with insulin secretion in the absence of marked changes in blood glucose or with a direct effect of aspartame itself on beta-endorphin liberation.