Homeostatic-like Potentiation of the Aversive Habenulo-raphe Pathway in an Animal Model of Post-stroke Depression

• Main Author: Maillé, Sébastien
• Other Authors: Beiques, Jean-Claude
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2018
• Subjects: Stroke; Depression; Habenula; Dorsal Raphe Nucleus; Prefrontal cortex; Homeostatic plasticity
• Online Access: http://hdl.handle.net/10393/37287; http://dx.doi.org/10.20381/ruor-21559

Stroke is the third leading cause of death and the primary cause of adult long-term disability in Canada. Despite advances in rehabilitation research, stroke survivors experience an unusually high incidence of depressive symptoms which undermine recovery outcomes by reducing patient motivation levels. Human and animal studies have linked the incidence of post-stroke depression and the extent of prefrontal cortex (PFC) damage. The PFC and the lateral habenula (LHb) are limbic structures that are strongly connected to the serotonergic dorsal raphe nucleus (DRN), a key neuronal hub for mood regulation. We hypothesized that PFC stroke produces a depressive phenotype by triggering maladaptive reorganization in mood-related networks. We used viral and optogenetic strategies to functionally characterize PFC and LHb projections to DRN. Moreover, we found that PFC stroke causes a time-dependent remodeling of LHb inputs to DRN 5-HT neurons which results in altered postsynaptic glutamate receptor number and subunit composition. This remodeling likely reflects a homeostatic upregulation of LHb-DRN synapses in response to stroke-induced challenge to network activity. Since these synapses encode stress and aversion, potentiation of this pathway could contribute to depressive symptoms following stroke. However, more work will be needed to identify the behavioral and network-level consequences of altered LHb-DRN dynamics. Thus, a deeper understanding of circuit mechanisms implicated in post-stroke depression will provide insights into this disease and open new treatment avenues to improve recovery.