Behavorial and molecular responsed genereted in rat brain structures upon a feeding behavior paradigm

Abstract

Classic non-homeostatic structures involved in food intake regulation are reciprocally influenced by metabolic signals. Orexigenic peptides expressed in the olfactory bulb (OB) and hippocampus (HP) modulate olfactory processing and memory, respectively. Hypothalamic circuits also modulate feeding behavior by activating and releasing AgRP in response to peripheral orexigenic signals. Adequate feeding in response to fasting states requires the expression of p75NTR in AgRP neurons. Given the close relation between different feeding structures, we questioned whether there may be a similar role for p75NTR and AgRP in the OB and HP on the consummatory ingestive behavior of fed and fasted rats. Female rats were divided as: 1) control group (n = 5) fed ad libitum (ALD), and 2) an experimental fasted group (FG) (n = 5) undergoing 4 h of food deprivation. Rats were confronted with a T-maze containing a chow pellet (CP) and an avocado extract-coated pellet (AVO) and allowed to explore and consume either pellet of choice. OB and HP were dissected for histology analysis and p75NTR and AgRP gene expression was analyzed by means of RT-PCR. We found that FG rats were significantly faster when performing feeding tasks compared to ALD rats (median latencies: 46.6” vs 2’ 46”, p= 0.032). Both, FG and ALD rats consumed higher portions of AVO in comparison to CP (total consumption: FG, 10.4 ± 0.7 g AVO vs 6.5 ± 0.8 g CP; ALD, 8.7 ± 0.8 g AVO vs 3.1 ± 0.3 g CP), however these results did not show statistical significance. AgRP RNA was not expressed in the HP of neither FG nor ALD rats, however, was expressed in the OB of both groups. p75NTR RNA was expressed in the HP and OB of FG rats. In conclusion, metabolic states motivate different behavioral feeding responses in rats as suggested by shorter latencies to feed in the FG group, and induce the expression of p75NTR and AgRP in brain structures associated with non-homeostatic food intake regulation.