Patterns of Arc mRNA expression in the rat brain following dual recall of fear- and reward-based socially acquired information

Abstract

Learning can occur via direct experience or through observation of another individual (i.e., social learning). While research focused on understanding the neural mechanisms of direct learning is prevalent, less work has examined the brain circuitry mediating the acquisition and recall of socially acquired information. Here, we aimed to further elucidate the mechanisms underlying recall of socially acquired information by having male and female rats sequentially recall a socially transmitted food preference (STFP) and a fear association via fear conditioning by-proxy (FCbP). Brain tissue was processed for mRNA expression of the immediate early gene (IEG) Arc, which expresses in the nucleus following transcription before migrating to the cytoplasm over the next 25 min. Given this timeframe, we could identify whether Arc transcription was triggered by STFP recall, FCbP recall, or both. Contrary to past research, we found no differences in any Arc expression measures across a number of prefrontal regions and the ventral CA3 of the hippocampus between controls, demonstrators, and observers. We theorize that these results may indicate that relatively little Arc-dependent neural restructuring is taking place in the prefrontal cortices and ventral CA3 following recall of recently socially acquired information or directly acquired fear associations in these areas.

Estrous cycle state-dependent renewal of appetitive behavior recruits unique patterns of Arc mRNA in female rats

“…All FISH procedures occurred in an RNAse free environment using procedures modified from Lee et al (2016) , Agee et al (2023) . One full brain series from each rat containing the mPFC, amygdala, dHPC, and vHPC was processed; two brains were excluded due to tissue damage.…”

“…Once identified, both FITC and DAPI images were taken under 40× objective and these images were compiled using a custom macro script with ImageJ (NIH, Bethesda, MD, USA) software. Because the microscope used was not confocal, samples were collected from a single plane at various levels for each region of interest like in Agee et al (2023) . Specifically, one sample for each coordinate was taken from two subregions of the mPFC: the prelimbic (PL; +4.20, +3.60, and +3.20 mm from Bregma) and infralimbic (IL; +3.20 and +2.80 mm) cortices.…”