Taking a compassionate approach to the non-human animals used in biomedical research is in line with emerging ideas around a "culture of care". It is important to expose biomedical sciences students to the concept of a culture of care at an early stage and give them opportunities to explore related practices and ideas. However, there is no simple tool to explore biomedical sciences students' attitudes towards laboratory animals.
View Article and Find Full Text PDFIn the present experiments, we tested the conclusion from previous electrophysiological experiments that gavage of sweet food and systemically applied insulin both stimulate oxytocin secretion. To do so, we measured oxytocin secretion from urethane-anaesthetised male rats, and demonstrated a significant increase in secretion in response to gavage of sweetened condensed milk but not isocaloric cream, and a significant increase in response to intravenous injection of insulin. We compared the measurements made in response to sweetened condensed milk with the predictions from a computational model, which we used to predict plasma concentrations of oxytocin from the published electrophysiological responses of oxytocin cells.
View Article and Find Full Text PDFThe supramammillary nucleus (SuM) has an emerging role in appetite control. We have shown that the rat SuM is activated during hunger or food anticipation, or by ghrelin administration. In the present study, we characterised the connectivity between the SuM and key appetite- and motivation-related nuclei in the rat.
View Article and Find Full Text PDFThe circulating orexigenic hormone ghrelin targets many brain areas involved in feeding control and signals via a dedicated receptor, the growth hormone secretagogue receptor 1A. One unexplored target area for ghrelin is the supramammillary nucleus (SuM), a hypothalamic area involved in motivation and reinforcement and also recently linked to metabolic control. Given that ghrelin binds to the SuM, we explored whether SuM cells respond to ghrelin and/or are activated when endogenous ghrelin levels are elevated.
View Article and Find Full Text PDFOxytocin is a potent anorexigen and is believed to have a role in satiety signaling. We developed rat models to study the activity of oxytocin neurons in response to voluntary consumption or oral gavage of foods using c-Fos immunohistochemistry and in vivo electrophysiology. Using c-Fos expression as an indirect marker of neural activation, we showed that the percentage of magnocellular oxytocin neurons expressing c-Fos increased with voluntary consumption of sweetened condensed milk (SCM).
View Article and Find Full Text PDFRelease of neuroactive substances by exocytosis from dendrites is surprisingly widespread and is not confined to a particular class of transmitters: it occurs in multiple brain regions, and includes a range of neuropeptides, classical neurotransmitters, and signaling molecules, such as nitric oxide, carbon monoxide, ATP, and arachidonic acid. This review is focused on hypothalamic neuroendocrine cells that release vasopressin and oxytocin and midbrain neurons that release dopamine. For these two model systems, the stimuli, mechanisms, and physiological functions of dendritic release have been explored in greater detail than is yet available for other neurons and neuroactive substances.
View Article and Find Full Text PDFHealth nudge interventions to steer people into healthier lifestyles are increasingly applied by governments worldwide, and it is natural to look to such approaches to improve health by altering what people choose to eat. However, to produce policy recommendations that are likely to be effective, we need to be able to make valid predictions about the consequences of proposed interventions, and for this, we need a better understanding of the determinants of food choice. These determinants include dietary components (e.
View Article and Find Full Text PDFObesity (Silver Spring)
October 2016
Objective: Energy intake is regulated by overlapping homeostatic and hedonic systems. Consumption of palatable foods has been implicated in weight gain, but this assumes that homeostatic control systems do not accurately detect this hedonically driven energy intake. This study tested this assumption, hypothesizing that satiated rats would reduce their voluntary food intake and maintain a stable body weight after consuming a palatable food.
View Article and Find Full Text PDF"Food addiction" has become a focus of interest for researchers attempting to explain certain processes and/or behaviors that may contribute to the development of obesity. Although the scientific discussion on "food addiction" is in its nascent stage, it has potentially important implications for treatment and prevention strategies. As such, it is important to critically reflect on the appropriateness of the term "food addiction", which combines the concepts of "substance-based" and behavioral addiction.
View Article and Find Full Text PDFFlaring and warping of the disk of the Milky Way have been inferred from observations of atomic hydrogen but stars associated with flaring have not hitherto been reported. In the area beyond the Galactic centre the stars are largely hidden from view by dust, and the kinematic distances of the gas cannot be estimated. Thirty-two possible Cepheid stars (young pulsating variable stars) in the direction of the Galactic bulge were recently identified.
View Article and Find Full Text PDFAlmost all circulating gut peptides contribute to the control of food intake by signalling satiety. One important exception is ghrelin, the only orexigenic peptide hormone thus far described. Ghrelin secretion increases before meals and behavioural and electrophysiological evidence shows that ghrelin acts in the hypothalamus via homeostatic pathways to signal hunger and increase food intake and adiposity.
View Article and Find Full Text PDFOxytocin neurons have a physiological role in food intake and energy balance. Central administration of oxytocin is powerfully anorexigenic, reducing food intake and meal duration. The central mechanisms underlying this effect of oxytocin have become better understood in the past few years.
View Article and Find Full Text PDFDecisions about what, when and how much to eat are made by the brain, though these choices can be strongly influenced by the hedonic and rewarding properties of sweet or fatty foods. The rumbling before and the fullness after eating tells us that the gut also has an important role in the initiation and termination of feeding. Gut-derived peptides continually convey homeostatic information to the brain to guide feeding.
View Article and Find Full Text PDFNeurobiological mechanisms that normally control food intake and energy expenditure can be overcome by environmental cues and by stress. Of particular importance is the influence of the mesolimbic reward pathway. In genetically susceptible individuals, problematic over-eating likely reflects a changing balance in the control exerted by homeostatic versus reward circuits that are strongly influenced by environmental factors such as stress.
View Article and Find Full Text PDFThe pleasure derived from eating may feel like a simple emotion, but the decision to eat, and perhaps more importantly what to eat, involves central pathways linking energy homeostasis and reward and their regulation by metabolic and endocrine factors. Evidence is mounting that modulation of the hedonic aspects of energy balance is under the control of peripheral neuropeptides conventionally associated with homeostatic appetite control. Here, we describe the significance of reward in feeding, the neural substrates underlying the reward pathway and their modification by peptides released into the circulation from peripheral tissues.
View Article and Find Full Text PDFBackground: Vestibulo-ocular reflex (VOR) gain adaptation, a longstanding experimental model of cerebellar learning, utilizes sites of plasticity in both cerebellar cortex and brainstem. However, the mechanisms by which the activity of cortical Purkinje cells may guide synaptic plasticity in brainstem vestibular neurons are unclear. Theoretical analyses indicate that vestibular plasticity should depend upon the correlation between Purkinje cell and vestibular afferent inputs, so that, in gain-down learning for example, increased cortical activity should induce long-term depression (LTD) at vestibular synapses.
View Article and Find Full Text PDFThere is very little published information about the outcomes of patients treated by telemedicine in developing countries. Over a two-year period, seven medical students from five universities spent their electives at a hospital in Papua New Guinea. They assisted with the review of a total of 44 e-referrals made by local doctors; the referrals resulted in 61 queries in a wide range of specialties.
View Article and Find Full Text PDFP2X receptors are adenosine 5'-triphosphate (ATP)-gated cation-selective channels. Seven cloned subunits (P2X(1-7)) are found in the plasma membrane of many cells in the brain and periphery. ATP-dependent opening of nuclear membrane channels, which resemble P2X(7) receptors, has been reported previously.
View Article and Find Full Text PDF