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Prefrontal dopamine regulates fear reinstatement through the downregulation of extinction circuits.

Hitora-Imamura N, Miura Y, Teshirogi C, Ikegaya Y, Matsuki N, Nomura H - Elife (2015)

Bottom Line: By utilising a contextual fear-conditioning task in mice, we found that reinstatement was accompanied by decreased c-Fos expression in the infralimbic cortex (IL) with reduction of synaptic input and enhanced c-Fos expression in the medial subdivision of the central nucleus of the amygdala (CeM).Moreover, we found that IL dopamine plays a key role in reinstatement.A reinstatement-inducing reminder shock induced c-Fos expression in the IL-projecting dopaminergic neurons in the ventral tegmental area, and the blocking of IL D1 signalling prevented reduction of synaptic input, CeM c-Fos expression, and fear reinstatement.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.

ABSTRACT
Prevention of relapses is a major challenge in treating anxiety disorders. Fear reinstatement can cause relapse in spite of successful fear reduction through extinction-based exposure therapy. By utilising a contextual fear-conditioning task in mice, we found that reinstatement was accompanied by decreased c-Fos expression in the infralimbic cortex (IL) with reduction of synaptic input and enhanced c-Fos expression in the medial subdivision of the central nucleus of the amygdala (CeM). Moreover, we found that IL dopamine plays a key role in reinstatement. A reinstatement-inducing reminder shock induced c-Fos expression in the IL-projecting dopaminergic neurons in the ventral tegmental area, and the blocking of IL D1 signalling prevented reduction of synaptic input, CeM c-Fos expression, and fear reinstatement. These findings demonstrate that a dopamine-dependent inactivation of extinction circuits underlies fear reinstatement and may explain the comorbidity of substance use disorders and anxiety disorders.

No MeSH data available.


Related in: MedlinePlus

A reminder shock activates dopaminergic VTA neurons projecting to the IL.(A) Coronal brain section of a mouse with Alexa 488-conjugated cholera toxin subunit B (CTB) infusion into the IL. (B) A representative immunofluorescence image of the ventral tegmental area (VTA) neurons with c-Fos, tyrosine hydroxylase (TH), and CTB. (C) A reminder shock increased the proportion of c-Fos+ neurons in IL-projecting TH+ VTA neurons (no shock: n = 7, reminder shock: n = 6 mice; t(11) = 4.3, p = 0.0012). (D) A reminder shock did not increase the proportion of c-Fos+ neurons in IL-projecting TH− VTA neurons (no shock: n = 7, reminder shock: n = 6 mice). **p < 0.01, Data represent mean ± standard error.DOI:http://dx.doi.org/10.7554/eLife.08274.011
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fig3: A reminder shock activates dopaminergic VTA neurons projecting to the IL.(A) Coronal brain section of a mouse with Alexa 488-conjugated cholera toxin subunit B (CTB) infusion into the IL. (B) A representative immunofluorescence image of the ventral tegmental area (VTA) neurons with c-Fos, tyrosine hydroxylase (TH), and CTB. (C) A reminder shock increased the proportion of c-Fos+ neurons in IL-projecting TH+ VTA neurons (no shock: n = 7, reminder shock: n = 6 mice; t(11) = 4.3, p = 0.0012). (D) A reminder shock did not increase the proportion of c-Fos+ neurons in IL-projecting TH− VTA neurons (no shock: n = 7, reminder shock: n = 6 mice). **p < 0.01, Data represent mean ± standard error.DOI:http://dx.doi.org/10.7554/eLife.08274.011

Mentions: The mPFC, including the IL, receives dopaminergic innervation from the ventral tegmental area (VTA). It is reported that aversive stimuli activate VTA dopaminergic neurons (Matsumoto and Hikosaka, 2009; Brischoux et al., 2009) and elevate dopamine concentration in the PFC (Abercrombie et al., 1989; Hamamura and Fibiger, 1993). Additionally, dopamine application with electric stimulation suppresses transmitter release onto mPFC neurons via dopamine D1 receptors (D1Rs) (Law-Tho et al., 1994; Gao et al., 2001). Therefore, we hypothesised that a reminder shock activates the VTA-to-IL circuit and that dopamine D1 signalling in the IL contributes to reduction of synaptic input onto IL neurons and subsequent fear reinstatement. In order to assess this idea, we tested whether a reminder shock induces c-Fos expression in the VTA neurons projecting to the IL. We retrogradely labelled the neurons projecting to the IL by infusing Alexa 488-conjugated cholera toxin subunit B (CTB) into the IL (Figure 3A). Of the retrogradely labelled cells (CTBIL+) in the VTA, 59.1 ± 4.5% were immunopositive for a dopamine neuron marker, tyrosine hydroxylase (TH+), indicating that they were dopaminergic. This is within the range reported in previous studies (Margolis et al., 2006; Lammel et al., 2011). The mice underwent conditioning, extinction training, test 1, and were exposed to chamber B with or without a reminder shock; their brains were removed 90 min later. c-Fos and TH were immunostained and observed in the VTA (Figure 3B). We found that a reminder shock increased c-Fos expression in the CTBIL+ TH+ VTA neurons (Figure 3C), but not in the CTBIL+ TH− VTA neurons (Figure 3D). This result suggests that a reminder shock activates dopaminergic VTA neurons projecting to the IL.10.7554/eLife.08274.011Figure 3.A reminder shock activates dopaminergic VTA neurons projecting to the IL.


Prefrontal dopamine regulates fear reinstatement through the downregulation of extinction circuits.

Hitora-Imamura N, Miura Y, Teshirogi C, Ikegaya Y, Matsuki N, Nomura H - Elife (2015)

A reminder shock activates dopaminergic VTA neurons projecting to the IL.(A) Coronal brain section of a mouse with Alexa 488-conjugated cholera toxin subunit B (CTB) infusion into the IL. (B) A representative immunofluorescence image of the ventral tegmental area (VTA) neurons with c-Fos, tyrosine hydroxylase (TH), and CTB. (C) A reminder shock increased the proportion of c-Fos+ neurons in IL-projecting TH+ VTA neurons (no shock: n = 7, reminder shock: n = 6 mice; t(11) = 4.3, p = 0.0012). (D) A reminder shock did not increase the proportion of c-Fos+ neurons in IL-projecting TH− VTA neurons (no shock: n = 7, reminder shock: n = 6 mice). **p < 0.01, Data represent mean ± standard error.DOI:http://dx.doi.org/10.7554/eLife.08274.011
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Related In: Results  -  Collection

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fig3: A reminder shock activates dopaminergic VTA neurons projecting to the IL.(A) Coronal brain section of a mouse with Alexa 488-conjugated cholera toxin subunit B (CTB) infusion into the IL. (B) A representative immunofluorescence image of the ventral tegmental area (VTA) neurons with c-Fos, tyrosine hydroxylase (TH), and CTB. (C) A reminder shock increased the proportion of c-Fos+ neurons in IL-projecting TH+ VTA neurons (no shock: n = 7, reminder shock: n = 6 mice; t(11) = 4.3, p = 0.0012). (D) A reminder shock did not increase the proportion of c-Fos+ neurons in IL-projecting TH− VTA neurons (no shock: n = 7, reminder shock: n = 6 mice). **p < 0.01, Data represent mean ± standard error.DOI:http://dx.doi.org/10.7554/eLife.08274.011
Mentions: The mPFC, including the IL, receives dopaminergic innervation from the ventral tegmental area (VTA). It is reported that aversive stimuli activate VTA dopaminergic neurons (Matsumoto and Hikosaka, 2009; Brischoux et al., 2009) and elevate dopamine concentration in the PFC (Abercrombie et al., 1989; Hamamura and Fibiger, 1993). Additionally, dopamine application with electric stimulation suppresses transmitter release onto mPFC neurons via dopamine D1 receptors (D1Rs) (Law-Tho et al., 1994; Gao et al., 2001). Therefore, we hypothesised that a reminder shock activates the VTA-to-IL circuit and that dopamine D1 signalling in the IL contributes to reduction of synaptic input onto IL neurons and subsequent fear reinstatement. In order to assess this idea, we tested whether a reminder shock induces c-Fos expression in the VTA neurons projecting to the IL. We retrogradely labelled the neurons projecting to the IL by infusing Alexa 488-conjugated cholera toxin subunit B (CTB) into the IL (Figure 3A). Of the retrogradely labelled cells (CTBIL+) in the VTA, 59.1 ± 4.5% were immunopositive for a dopamine neuron marker, tyrosine hydroxylase (TH+), indicating that they were dopaminergic. This is within the range reported in previous studies (Margolis et al., 2006; Lammel et al., 2011). The mice underwent conditioning, extinction training, test 1, and were exposed to chamber B with or without a reminder shock; their brains were removed 90 min later. c-Fos and TH were immunostained and observed in the VTA (Figure 3B). We found that a reminder shock increased c-Fos expression in the CTBIL+ TH+ VTA neurons (Figure 3C), but not in the CTBIL+ TH− VTA neurons (Figure 3D). This result suggests that a reminder shock activates dopaminergic VTA neurons projecting to the IL.10.7554/eLife.08274.011Figure 3.A reminder shock activates dopaminergic VTA neurons projecting to the IL.

Bottom Line: By utilising a contextual fear-conditioning task in mice, we found that reinstatement was accompanied by decreased c-Fos expression in the infralimbic cortex (IL) with reduction of synaptic input and enhanced c-Fos expression in the medial subdivision of the central nucleus of the amygdala (CeM).Moreover, we found that IL dopamine plays a key role in reinstatement.A reinstatement-inducing reminder shock induced c-Fos expression in the IL-projecting dopaminergic neurons in the ventral tegmental area, and the blocking of IL D1 signalling prevented reduction of synaptic input, CeM c-Fos expression, and fear reinstatement.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.

ABSTRACT
Prevention of relapses is a major challenge in treating anxiety disorders. Fear reinstatement can cause relapse in spite of successful fear reduction through extinction-based exposure therapy. By utilising a contextual fear-conditioning task in mice, we found that reinstatement was accompanied by decreased c-Fos expression in the infralimbic cortex (IL) with reduction of synaptic input and enhanced c-Fos expression in the medial subdivision of the central nucleus of the amygdala (CeM). Moreover, we found that IL dopamine plays a key role in reinstatement. A reinstatement-inducing reminder shock induced c-Fos expression in the IL-projecting dopaminergic neurons in the ventral tegmental area, and the blocking of IL D1 signalling prevented reduction of synaptic input, CeM c-Fos expression, and fear reinstatement. These findings demonstrate that a dopamine-dependent inactivation of extinction circuits underlies fear reinstatement and may explain the comorbidity of substance use disorders and anxiety disorders.

No MeSH data available.


Related in: MedlinePlus