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Ciliary neurotrophic factor signaling in the rat orbitofrontal cortex ameliorates stress-induced deficits in reversal learning.

ABSTRACT: Deficits in cognitive flexibility, i.e. the ability to modify behavior in response to changes in the environment, are present in several psychiatric disorders and are often refractory to treatment. However, improving treatment response has been hindered by a lack of understanding of the neurobiology of cognitive flexibility. Using a rat model of chronic stress (chronic intermittent cold stress, CIC) that produces selective deficits in reversal learning, a form of cognitive flexibility dependent on orbitofrontal cortex (OFC) function, we have previously shown that JAK2 signaling is required for optimal reversal learning. In this study we explore the molecular basis of those effects. We show that, within the OFC, CIC stress reduces the levels of phosphorylated JAK2 and of ciliary neurotrophic factor (CNTF), a promoter of neuronal survival and an activator of JAK2 signaling, and that neutralizing endogenous CNTF with an intra-OFC microinjection of a specific antibody is sufficient to produce reversal-learning deficits similar to stress. Intra-OFC delivery of recombinant CNTF to CIC-stressed rats, at a dose that induces JAK2 and Akt but not STAT3 or ERK, ameliorates reversal-learning deficits, and Akt blockade prevents the positive effects of CNTF. Further analysis revealed that CNTF may exert its beneficial effects by inhibiting GSK3?, a substrate of Akt and a regulator of protein degradation. We also revealed a novel mechanism of CNTF action through modulation of p38/Mnk1/eIF4E signaling. This cascade controls translation of select mRNAs, including those encoding several plasticity-related proteins. Thus, we suggest that CNTF-driven JAK2 signaling corrects stress-induced reversal learning deficits by modulating the steady-state levels of plasticity-related proteins in the OFC.

SUBMITTER: Girotti M

PROVIDER: S-EPMC6842063 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Ciliary neurotrophic factor signaling in the rat orbitofrontal cortex ameliorates stress-induced deficits in reversal learning.

Girotti Milena M Silva Jeri D JD George Christina M CM Morilak David A DA

Neuropharmacology 20190922

Deficits in cognitive flexibility, i.e. the ability to modify behavior in response to changes in the environment, are present in several psychiatric disorders and are often refractory to treatment. However, improving treatment response has been hindered by a lack of understanding of the neurobiology of cognitive flexibility. Using a rat model of chronic stress (chronic intermittent cold stress, CIC) that produces selective deficits in reversal learning, a form of cognitive flexibility dependent ...[more]

PMID: 31553898

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Project description:BackgroundDistinguishing between actions that are more likely or less likely to be rewarded is a critical aspect of goal-directed decision making. However, neuroanatomic and molecular mechanisms are not fully understood.MethodsWe used anterograde tracing, viral-mediated gene silencing, functional disconnection strategies, pharmacologic rescue, and designer receptors exclusively activated by designer drugs (DREADDs) to determine the anatomic and functional connectivity between the orbitofrontal cortex (OFC) and the amygdala in mice. In particular, we knocked down brain-derived neurotrophic factor (Bdnf) bilaterally in the OFC or generated an OFC-amygdala "disconnection" by pairing unilateral OFC Bdnf knockdown with lesions of the contralateral amygdala. We characterized decision-making strategies using a task in which mice selected actions based on the likelihood that they would be reinforced. Additionally, we assessed the effects of DREADD-mediated OFC inhibition on the consolidation of action-outcome conditioning.ResultsAs in other species, the OFC projects to the basolateral amygdala and dorsal striatum in mice. Bilateral Bdnf knockdown within the ventrolateral OFC and unilateral Bdnf knockdown accompanied by lesions of the contralateral amygdala impede goal-directed response selection, implicating BDNF-expressing OFC projection neurons in selecting actions based on their consequences. The tyrosine receptor kinase B agonist 7,8-dihydroxyflavone rescues action selection and increases dendritic spine density on excitatory neurons in the OFC. Rho-kinase inhibition also rescues goal-directed response strategies, linking neural remodeling with outcome-based decision making. Finally, DREADD-mediated OFC inhibition weakens new action-outcome memory.ConclusionsActivity-dependent and BDNF-dependent neuroplasticity within the OFC coordinate outcome-based decision making through interactions with the amygdala. These interactions break reward-seeking habits, a putative factor in multiple psychopathologies.

Dataset Information

Ciliary neurotrophic factor signaling in the rat orbitofrontal cortex ameliorates stress-induced deficits in reversal learning.

Publications

Ciliary neurotrophic factor signaling in the rat orbitofrontal cortex ameliorates stress-induced deficits in reversal learning.

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