Expression of c-Fos following voluntary ingestion of a novel or familiar taste in rats

Abstract

Taste neophobia, the rejection of novel tastes or foods, involves an interplay of various brain regions encompassing areas within the central gustatory system, as well as nuclei serving other functions. Previous findings, utilising c-Fos imaging, identified several brain regions which displayed higher activity after ingestion of a novel taste as compared to a familiar taste. The present study extends this analysis to include additional regions suspected of contributing to the neurocircuitry involved in evoking taste neophobia. Our data show increased c-Fos expression in the basolateral amygdala, central nucleus of the amygdala, gustatory portion of the thalamus, gustatory portion of the insular cortex and the medial and lateral regions of the parabrachial nucleus. These results confirm the contribution of areas previously identified as active during ingestion of novel tastes and expose additional areas that express elevated levels of c-Fos under these conditions, thus adding to the neural network involved in the detection and initial processing of taste novelty.

Keywords: Innate aversive response; Neophobic reaction; Rat; Unknown taste; c-Fos.

Fig 1.

Mean (±SE) number of c-Fos positive nuclei following ingestion of novel or familiar 0.3% saccharin solution in: rostral nucleus of the solitary tract (rNST), medial parabrachial nucleus (mPBN), lateral parabrachial nucleus (lPBN), gustatory thalamus (GT), gustatory cortex (GC), central nucleus of the amygdala (CNA), medial nucleus of the amygdala (MeA), basolateral nucleus of the amygdala (BLA), bed nucleus of the stria terminalis (BNST), lateral hypothalamus (LH), nucleus accumbens core (NAcC), nucleus accumbens shell (NAcS), nucleus basalis magnocellularis (NBM), perirhinal cortex (PrC). * Significant at p<0.05

Fig 2.

Representative digital images of c-Fos immunostaining in animals that displayed a significantly higher number of c-Fos positive cells in the novel group (left column) than the familiar group (right column) within the medial parabrachial nucleus (mPBN), lateral parabrachial nucleus (lPBN), gustatory thalamus (GT), gustatory cortex (GC), central nucleus of the amygdala (CNA), basolateral amygdala (BLA). Additional abbreviations: Cl, claustrum; CPu, caudate putamen; fr, fasciculus retroflexus; rf, rhinal fissure.