The induction of c-Fos in the NTS after taste aversion learning is not correlated with measures of conditioned fear

The induction of c-Fos-like immunoreactivity (c-FLI) in the nucleus of the solitary tract (NTS) has been shown to be correlated with behavioral expres sion of a conditioned taste aversion (CTA). However, because this cellular response is also dependent on an intact amygdala, it may represent the acti vation of a stress-related autonomic response. The present experiments addr essed this possibility by evaluating the correlation between c-FLI in the i ntermediate division of the NTS (iNTS) and 2 measures of conditioned fear: freezing and changes in mean arterial pressure (MAP) and heart rate (HR). E xposure to the taste conditioned stimulus (CS) resulted in a marked inducti on of c-FLI in the iNTS, whereas exposure to a fear CS did not. Further, ex posure to a taste CS did not selectively lead to increases in MAP or HR. Re sults suggest that induction of c-FLI in the iNTS may reflect the activatio n of a cell population whose function is unique to the CTA paradigm.