Epigenetic Modifications in the Rat Neonate Olfactory Bulb and Anterior Piriform Cortex Associated with Olfactory and Tactile Experiences

Abstract

Rodents are macrosmatic; they depend heavily on the olfactory system, which includes the olfactory bulb and anterior piriform cortex, to navigate their environment. The olfactory system is key to the survival of neonatal pups in order to learn the scents of the dam, which aid in nipple attachment and overall attachment to the caregiver. This attachment‐based learning was mimicked in rodents using a laboratory‐based experimental design in which neonatal pups were classically conditioned to associate the novel scent of peppermint with stroking, an action that mimics sensory cues associated with caregiving. The effects of attachment‐based learning on mRNA levels of epigenetic regulators, as well as epigenetic modifications of Bdnf and Reln, genes involved in neuroplasticity, are unknown.We investigated changes in gene expression of Bdnf, Reln, and epigenetic regulators (DNMT1, DNMT3a, DNMT3b, HDAC1, HDAC2, HDAC5, TET1, Gadd45B, and MeCP2) following infant olfactory learning. Using an odor‐stroke paradigm, Long‐Evans rat pups (postnatal days 6 or 7) (n=46) were assigned to either a paired (simultaneous peppermint odor and stroking), unpaired (non‐simultaneous peppermint odor and stroking), or odor‐/stroke‐only condition. Brains were harvested 30 minutes after conditioning. Using Real‐time PCR, we found experience‐induced changes in gene expression profiles in both brain regions. For example, Bdnf exon IV gene expression in the olfactory bulb significantly increased in rats that received contiguous presentation of both stimuli; however, gene expression of HDAC2, HDAC5, TET1, and Gadd45B significantly decreased in the same subjects. In the anterior piriform cortex, there were significant increases in gene expression of Bdnf exons I and IV, DNMT3b, and Gadd45B in both paired and unpaired subjects. Understanding the unknown epigenetic modifications involved in attachment‐based learning may elucidate the mechanisms of the emotional connection an infant learns for the caregiver and its profound influence on neurological development.Support or Funding InformationSpecial thanks to Dr. Roth and Tiffany Doherty for their support and guidance along with Lauren Webb's and Tiffany's completion of odor‐stroke conditioning. This research is funded through grants P20GM103653, R01HD087509, and private donation funds to Dr. Roth.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.