2020 |
Mcgowan, Josephine |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
Elucidating the Mechanisms Underlying Ketamine-Induced Protection Against Fear Overgeneralization @ Columbia University Health Sciences
PROJECT SUMMARY / ABSTRACT Though stress is necessary for the adaptive survival of a species, stress exposure can also elicit maladaptive physiological and behavioral responses. Chronic stress in particular often leads to maladaptive responses, and subsequent development of psychiatric disorders such as post-traumatic stress disorder (PTSD) and major depressive disorder (MDD). A core symptom observed in these disorders is increased fear generalization, as defined by the overgeneralization of fear from a conditioned, fear-inducing stimulus to novel, neutral stimuli. We have previously discovered that a single injection of (R,S)-ketamine, a rapid-acting antidepressant, protects mice against stress-induced depressive-like behavior (Brachman et al., 2016) and attenuates learned fear following contextual fear conditioning (CFC) (McGowan et al., 2017). We have also found that, using a contextual fear discrimination (CFD) protocol, (R,S)-ketamine decreases fear generalization (Mastrodonato et al., 2018). The Denny laboratory has reported that the ventral hippocampus (vHPC), specifically ventral CA3 (vCA3), mediates (R,S)-ketamine's effects on attenuating learned fear in the CFC paradigm. However, how exactly (R,S)-ketamine modulates the ensembles in vCA3 to decrease fear generalization is yet to be explored. This research plan will lay the groundwork to uncover the effects of (R,S)-ketamine administration on fear generalization throughout CFD using a combination of in vivo microdialysis and in vivo Ca2+ imaging in vCA3. Both of these in vivo techniques will allow for chronic assessment of underlying changes throughout (R,S)- ketamine administration and during behavioral expression (e.g., fear overgeneralization). In Aim 1, I will test the hypothesis that neurochemical changes in glutamate, gamma-aminobutyric acid (GABA), and serotonin (5- HT) in vCA3 potentially mediate (R,S)-ketamine's effects on fear generalization in male and female mice. By using in vivo microdialysis, I will determine how neurotransmitters relevant to learning and memory are contributing to fear generalization in both saline (control)-injected and (R,S)-ketamine-injected mice. I will test the hypothesis that glutamate and 5-HT in vCA3 are persistently increased, while GABA is decreased, during expression of fear in saline-treated mice, but that this persistent increase is mitigated by (R,S)-ketamine treatment. In Aim 2, I will utilize nVoke minimicroscopes developed by Inscopix to perform in vivo Ca2+ imaging and will test the hypothesis that (R,S)-ketamine prevents the heightened excitatory Ca2+ activity in vCA3 induced by stress, and thus, decreases fear generalization in male and female mice. For Aim 2A, I will visualize Ca2+ transients in excitatory cells of vCA3. For Aim 2B, I will visualize Ca2+ transients in inhibitory cells of vCA3. To date, no longitudinal studies utilizing in vivo Ca2+ imaging or in vivo microdialysis studies have yet been performed for fear generalization and/or following (R,S)-ketamine administration. Overall, my goal for this proposal is to better understand how (R,S)-ketamine may alter neurotransmitters and neural ensembles, resulting in decreased fear generalization, a core symptom in PTSD and MDD patients.
|
1 |
2021 |
Mcgowan, Josephine |
F99Activity Code Description: To support the Pre-doctoral Phase of a Pre-doctoral to Post-doctoral transition award that provides 1-2 years of predoctoral support for highly motivated graduate students. The F99 activity code is intended to only be used in conjunction with a K00 Award |
Dissecting the Contribution of the Ventral Hippocampus to (R,S)-Ketamine's Fear Buffering Effects @ Columbia University Health Sciences
PROJECT SUMMARY / ABSTRACT Though stress is necessary for the adaptive survival of a species, stress exposure can also elicit maladaptive physiological and behavioral responses. Stress-induced maladaptive responses may lead to subsequent development of psychiatric disorders such as post-traumatic stress disorder (PTSD) and major depressive disorder (MDD). A core symptom observed in these disorders is increased fear expression, as defined by heightened fear responses in the presence of stimuli associated with fear. We have previously discovered that a single injection of (R,S)-ketamine, a rapid-acting antidepressant, attenuates learned fear following contextual fear conditioning (CFC). We and others have reported that the ventral hippocampus (vHPC), specifically ventral CA3 (vCA3), mediates (R,S)-ketamine?s effects on attenuating learned fear. However, how exactly (R,S)-ketamine modulates the ensembles in vCA3 to decrease fear generalization is yet to be explored. It has additionally been shown that ventral CA1 (vCA1) contributes to fear behavior. Thus, this research plan will lay the groundwork to uncover the effects of (R,S)-ketamine administration on fear behavior using of in vivo microdialysis to complement and further explain the data already collected from in vivo Ca2+ imaging in vCA3 and vCA1. Overall, my goal for this proposal is to better understand how (R,S)-ketamine alters neurotransmitters and neuronal ensembles to buffer against heightened fear expression. My preliminary findings outlined in Aim 1 show that (R,S)-ketamine: 1) blunts responses to shocks during fear encoding specifically in vCA3; 2) differentially affects activity in ventral hippocampal regions CA3 and CA1; and 3) decreases correlated activity in the ventral hippocampus during both fear encoding and retrieval. Together, these findings lead me to my hypothesis that there are distinct changes in neurotransmitter content immediately following (R,S)-ketamine administration that are long-lasting and that blunt the experience of a fearful stressor. However, to test this hypothesis, I need to utilize in vivo microdialysis as outlined in Aim 2 to measure levels of glutamate, gamma-aminobutyric acid (GABA), and serotonin (5-HT) in vCA3 or vCA1 of male and female mice to understand how they potentially mediate (R,S)-ketamine?s effects. To date, no longitudinal studies utilizing in vivo Ca2+ imaging or in vivo microdialysis studies have yet been performed investigating (R,S)-ketamine effects on fear behavior. In Aim 3, I describe a postdoctoral research direction to accomplish my goal of understanding the biological substrates of stress resilience. I have gained experience in behavior, in vivo techniques, cellular and molecular neuroscience, and microscopy. However, I have yet to conduct techniques that manipulate circuits, or that probe the contribution of transcriptomic changes after drug treatment or with stress. Thus, I plan to address these gaps in my knowledge by finding a post-doctoral position that allows me to grow in these skills. In summary, this proposal will lead to the development of a diverse skillset in order to become a successful independent researcher in the psychiatric field.
|
1 |