Fos-like immunoreactivity in vagal and hypoglossal nuclei in different feeding states: a quantitative study

This study characterized the distribution of Fos-like immunoreactivity (FLI) in three hindbrain nuclei: dorsal motor nucleus of the vagus (DMN), nucleus of the solitary tract (NST) and hypoglossal nucleus (HG) in response to eating or activation of specific components of feeding behavior. The degree of FLI was quantified by automated image analysis software that provided an efficient and sensitive method for counting the number of cells labelled with Fos antibody. Ingestion, and anticipation, of a meal both increased FLI in the DMN and HG, but not in the NST. Sham feeding 1 M sucrose was a more potent stimulus for FLI activation in DMN and NST than combined oral plus gastric/postingestive stimulation provided by real feeding the same food. The results indicate that the physiological stimulus of eating is sufficient to elicit FLI in the hindbrain and that specific components of the feeding act, especially oral stimulation provided by sham feeding, can activate FLI. The results suggest further that, under specific experimental conditions, gastric and/or postgastric stimulation may decrease FLI in the NST and DMN.