Recruitment of Hippocampal and Thalamic Pathways to the Central Amygdala in the Control of Feeding Behavior Under Novelty

It is adaptive to restrict eating under uncertainty, such as during habituation to novel foods and unfamiliar environments. However, sustained restrictive eating is a core symptom of eating disorders and has serious long-term health consequences. Current therapeutic efforts are limited, because the neural substrates of restrictive eating are poorly understood. Using a model of feeding avoidance under novelty, our recent study identified forebrain activation patterns and found evidence that the central nucleus of the amygdala (CEA) is a core integrating node. The current study analyzed the activity of CEA inputs in male and female rats to determine if specific pathways are recruited during feeding under novelty. Recruitment of direct inputs from the paraventricular nucleus of the thalamus (PVT), the infralimbic cortex (ILA), the agranular insular cortex (AI), the hippocampal ventral field CA1, and the bed nucleus of the stria terminals (BST) was assessed with combined retrograde tract tracing and Fos induction analysis. The study found that during consumption of a novel food in a novel environment, larger number of neurons within the PVTp and the CA1 that send monosynaptic inputs to the CEA were recruited compared to controls that consumed familiar food in a familiar environment. The ILA, AI, and BST inputs to the CEA were similarly recruited across conditions. There were no sex differences in activation of any of the pathways analyzed. These results suggest that the PVTp-CEA and CA1-CEA pathways underlie feeding inhibition during novelty and could be potential sites of malfunction in excessive food avoidance.