Stress‐induced hyperphagia? Characterising the activity of the ghrelin axis in male rats with high anxiety behaviour

While evidence is emerging that the temporal pattern of feeding may influence anxiety, it is unclear to what extent anxiety may itself impact spontaneous feeding behaviour. To address this, we have quantified spontaneous feeding, ghrelin secretion and adult hippocampal neurogenesis (AHN) in male low (LAB) and high (HAB) anxiety-behaviour rats. LAB and HAB rats showed the expected anxiogenic profile in the elevated plus-maze, HAB rats avoiding the open arms entirely. A 16% reduction in total food intake in HAB rats (p = .017) was due to a 35% reduction in light phase food consumption (p = .004). However, there were no significant changes in the number or duration of individual feeding events, and the 24-h feeding profile remained largely unaltered. Although basal circulating ghrelin was comparable in HAB and LAB rats, the 57% elevation in circulating ghrelin induced by a 24-h fast in LAB rats (p = .022) was completely abolished in HAB rats. In comparison with adult LAB rats, the number of newborn neurones (BrdU⁺/NeuN⁺) in the dentate gyrus of HAB rats was elevated by 68% and 103% in the sub-granular zone and granule cell layer, respectively (p = .0004 and p < .0001), these increases being observed across the rostro-caudal extent of the hippocampus. In contrast, the number of newborn non-neuronal (BrdU⁺/NeuN^-) cells was unaltered. Thus, even in the context of the marked anxiety in HAB rats, mild hypophagia occurs without significant alteration in feeding patterns. Despite a blunting of fasting-induced ghrelin release, elevated AHN suggests an appropriate feedback response to the increased anxiety-related behaviour.