A Method to Investigate the Role of DH and mPFC Interactions in Episodic-Like Memory Consolidation
Mentor 1
Karyn Frick
Mentor 2
Miranda Schwabe
Start Date
16-4-2021 12:00 AM
Description
Concurrent activity in both the dorsal hippocampus (DH) and medial prefrontal cortex (mPFC) is necessary for the consolidation of spatial memory in mice, however, the mechanisms by which these two regions interact are not fully understood. To investigate the role of these interactions in memory consolidation, we present preliminary work piloting a method to label and modulate activity of neurons projecting from DH to mPFC. First, we tested a retrograde Cre viral construct (pENN.AAVrg.hSyn.HI.eGFP-Cre.WPRE.SV40) that is taken up by axons and transported retrogradely to cell bodies of neurons. The retrograde Cre was infused into the mPFC, DH, or RE of young female mice, and brains were collected 3, 4, or 6 weeks later to determine the extent of viral expression in the cell bodies of projection neurons. Immediately after extraction, brains were flash frozen and were later sectioned using a cryostat, mounted on slides, and imaged using a fluorescent microscope. Imaging allowed us to identify that the 4-week timepoint is optimal for visualizing projections from DH to mPFC. Next, we combined the Cre-GFP AAV in the PFC with the Cre-dependent DREADD (pAAV-hSyn-dF-HA-KORD-IRES-mCitrine) in the DH and confirmed expression of the DREADD at 4 weeks. Because Cre recombinase can affect cell health and, therefore, affect behavior, we tested Cre-infused mice, as well as control mice receiving saline in the PFC, in open field, object recognition and object placement tasks to assess effects of Cre virus on anxiety, object recognition, and spatial memory. Future work will use this viral method to inactivate DH-mPFC projections to test their role in memory consolidation. The results from this and future studies will allow us to better understand the circuitry underlying memory formation and may lead to advances in treatments for alleviating memory dysfunction.
A Method to Investigate the Role of DH and mPFC Interactions in Episodic-Like Memory Consolidation
Concurrent activity in both the dorsal hippocampus (DH) and medial prefrontal cortex (mPFC) is necessary for the consolidation of spatial memory in mice, however, the mechanisms by which these two regions interact are not fully understood. To investigate the role of these interactions in memory consolidation, we present preliminary work piloting a method to label and modulate activity of neurons projecting from DH to mPFC. First, we tested a retrograde Cre viral construct (pENN.AAVrg.hSyn.HI.eGFP-Cre.WPRE.SV40) that is taken up by axons and transported retrogradely to cell bodies of neurons. The retrograde Cre was infused into the mPFC, DH, or RE of young female mice, and brains were collected 3, 4, or 6 weeks later to determine the extent of viral expression in the cell bodies of projection neurons. Immediately after extraction, brains were flash frozen and were later sectioned using a cryostat, mounted on slides, and imaged using a fluorescent microscope. Imaging allowed us to identify that the 4-week timepoint is optimal for visualizing projections from DH to mPFC. Next, we combined the Cre-GFP AAV in the PFC with the Cre-dependent DREADD (pAAV-hSyn-dF-HA-KORD-IRES-mCitrine) in the DH and confirmed expression of the DREADD at 4 weeks. Because Cre recombinase can affect cell health and, therefore, affect behavior, we tested Cre-infused mice, as well as control mice receiving saline in the PFC, in open field, object recognition and object placement tasks to assess effects of Cre virus on anxiety, object recognition, and spatial memory. Future work will use this viral method to inactivate DH-mPFC projections to test their role in memory consolidation. The results from this and future studies will allow us to better understand the circuitry underlying memory formation and may lead to advances in treatments for alleviating memory dysfunction.
