Arguello, A. A. | bioRxiv Science

bioRxiv2021

Optogenetic inhibition of the dorsal hippocampus CA3 region during early-stage cocaine-memory reconsolidation disrupts subsequent context-induced cocaine seeking in rats

The dorsal hippocampus (DH) is key to the long-term maintenance of cocaine memories following retrieval-induced memory destabilization; even though, it is not the site of protein synthesis-dependent memory reconsolidation. Here, we took advantage of the temporal and spatial specificity of an optogenetic manipulation to examine the role of the cornu ammonis 3 subregion of the DH (dCA3) in early-stage cocaine-memory reconsolidation. Male Sprague-Dawley rats expressing eNpHR3.0 in the DH were trained to self-administer cocaine in a distinct context and underwent extinction training in a different context. Rats then received a 15-min memory-reactivation session, to destabilize cocaine memories and trigger reconsolidation, or remained in their home cages (no-reactivation controls). Optogenetic inhibition of the dCA3 for 1 h immediately, but not 1 h, after memory reactivation resulted in cocaine-memory impairment as indicated by reduction in drug-seeking behavior selectively in the cocaine-paired context 3 d later, at test, relative to responding in no-inhibition, no-reactivation, and no-eNpHR3.0 controls. Cocaine-memory impairment was associated with reduced c-Fos expression, an index of neuronal activation, in the dCA3 stratum lucidum (SL) and stratum pyramidale (SP) at test. Based on these observations and extant literature, we postulate that recurrent circuits in the SP are activated during early-stage memory reconsolidation to maintain labile cocaine memories prior to protein synthesis-dependent restabilization in another brain region, such as the basolateral amygdala. Furthermore, SL and SP interneurons may enhance memory reconsolidation by limiting synaptic noise in the SP and also contribute to recall as elements of the updated cocaine engram or retrieval links.

neuroscience↗

bioRxiv2020

SimpylCellCounter: An Automated Solution for Quantifying Cells in Brain Tissue

Rationale & ObjectiveManual quantification of activated cells can provide valuable information about stimuli-induced changes within brain regions; however, this analysis remains time intensive. Therefore, we created SimpylCellCounter (SCC), an automated method to quantify cells that express Cfos protein, an index of neuronal activity, in brain tissue and benchmarked it against two widely-used methods: OpenColonyFormingUnit (OCFU) and ImageJ Edge Detection Macro (IMJM). MethodsIn Experiment 1, manually-obtained counts were compared to those detected via OCFU, IMJM and SCC. The absolute error in counts (manual versus automated method) was calculated, and error types were categorized as false positives or negatives. In Experiment 2, performance analytics of OCFU, IMJM and SCC were compared. In Experiment 3, SCC performed analysis on images it was not trained on, to assess its general utility. Results & ConclusionsWe found SCC to be highly accurate and efficient in quantifying both cells with circular morphologies and those expressing Cfos. Additionally, SCC utilizes a new approach for counting overlapping cells with a pretrained convolutional neural network classifier. The current study demonstrates that SCC is a novel, automated tool to quantify cells in brain tissue, complementing current, open-sourced quantification methods designed to detect cells in vitro.

neuroscience↗