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Brain serotonin (5-HT) plays an important role in the regulation of food intake. The ingestive effects of 5-HT are mediated by a number of different receptor subtypes. The 5-HT1A receptor agonist 8-OH-DPAT produces hyperphagia or a decrease of food intake depending on animal feeding regime. These hyper- and hypophagic effects of the 5-HT1A receptor agonist have been the subject of many studies mostly carried out in rats. However, there is still little known if (1) the effects are mediated by presynaptic 5-HT1A autoreceptors in the raphe nuclei or by postsynaptic 5-HT1A receptors in serotonergic terminal structures and if (2) 8-OHDPAT has similar effects in other species. This study investigates the impact of 8-OH-DPAT administration on feeding behaviour in non- and food-deprived NMRI and C57BL mice as well as transgenic L35 mice, characterized by an overexpression of postsynaptic 5-HT1A receptors. Additionally, the microstructure of feeding, water intake and home cage activity were examined. 8-OH-DPAT increased food intake in non-deprived NMRI but not in C57BL mice and induced a hypophagic effect in food-deprived NMRI and C57BL mice. Preliminary data indicate neither a difference in feeding behaviour in L35 mice after 8-OH-DPAT administration nor a variety in the other parameters measured compared to control
mice. These results suggest a central role for the 5-HT1A receptor on feeding behaviour in mice, in which the hyperphagic effect of 8-OH-DPAT is most likely mediated by 5-HT1A autoreceptors.
Understanding the neurophysiology role of the 5-HT system on food intake may help to achieve new insights in disturbances of eating and body weight disorders.