Oleamide administered into the nucleus accumbens shell regulates feeding behaviour via CB1 and 5-HT2C receptors.

The central nervous system control of food intake has been extensively studied, hence, several neurotransmitter systems regulating this function are now clearly identified, for example, the endocannabinoid and serotoninergic systems. The former stimulates feeding while the latter inhibits it. Oleamide (Ole) is a cannabimimetic molecule affecting both systems. In this work, we tested the orexigenic and anorectic potential of Ole when administered into the nucleus accumbens shell (NAcS), a brain region that has been related to the orexigenic effects of cannabinoids. Additionally, we tested if Ole administered into this nucleus affects the activity of the hypothalamic nuclei involved in feeding behaviour, just as other cannabinoids do. We found a hyperphagic effect of Ole that is mediated through CB1 activation. The combination of Ole and the CB1 antagonist, AM251, produced a hypophagia that was fully blocked by SB212084, a 5-HT2C receptor antagonist. We also show that blockade of 5-HT2C and 5-HT2A receptors in the NAcS stimulates food intake. Finally, the combination of Ole and AM251 activates hypothalamic nuclei, an effect also blocked by SB242084. In conclusion, we show, for the first time, that Ole administered into the NAcS has a dual effect on feeding behaviour, acting through cannabinoid and serotonin receptors. These effects probably result from a downstream interaction with the hypothalamus.

Viewing Art in Different Contexts.

While aesthetic experiences are not limited to any particular context, their sensorial, cognitive and behavioral properties can be profoundly affected by the circumstances in which they occur. Given the ubiquitous nature of contextual effects in nearly all aspects of behavior, investigations aimed at delineating the context-dependent and context-independent aspects of aesthetic experience and engagement with aesthetic objects in a diverse range of settings are important in empirical aesthetics. Here, we analyze the viewing behavior of visitors (N = 19) freely viewing 15 paintings in the 20th-century Australian collection room at the Art Gallery of New South Wales. In particular, we focus on how aspects of viewing behavior including viewing distance in the gallery condition and eye gaze measures such as fixation count, total fixation duration and average fixation duration are affected by the artworks' physical characteristics including size and image statistics properties such as Fourier amplitude spectrum, fractal dimension and entropy. In addition, the same artworks were viewed in the laboratory, either scaled to fit most of the screen (N = 22) or to preserve their relative size as in the museum condition (N = 17) to assess the robustness of these relationships across different presentation contexts. We find that the effects of presentation context are modulated by the artworks' physical characteristics.

CB1R mediates oleamide's reward while 5HT2cR mediates aversion in the nucleus accumbens shell of rats.

In this study, we have pursued to assess oleamide's potential role in reward and aversion mechanisms. To reach this goal we infused oleamide, either 1 µg into the nucleus accumbens shell (NAccS) and evaluated its effects on conditioned place preference (CCP) or 10 µg, to evaluate conditioned place aversion (CPA). Extinction and reinstatement were also evaluated in both cases. We sought to determine if CPP occurs via cannabinoid receptor 1 (CB1R) and CPA via serontoninergic 2c receptor (5HT2cR). Results revealed that 1 µg of oleamide administered bilaterally into the NAccS induced CPP, while 10 µg induced CPA. In both conditions CPP or CPA, reinstatement after extinction was induced. AM251 (CB1R inverse-agonist) prevented CPP induced with 1 µg; while SB242084 (5HT2cR antagonist) not only prevented CPA induced with 10 µg but caused a switch to CPP. These results suggest that oleamide at low doses promotes reward through CB1R, and aversion at high doses via 5HT2cR.