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Parvalbumin-positive interneurons of the prefrontal cortex support working memory and cognitive flexibility.

Murray AJ, Woloszynowska-Fraser MU, Ansel-Bollepalli L, Cole KL, Foggetti A, Crouch B, Riedel G, Wulff P - Sci Rep (2015)

Bottom Line: It is however unclear, how impaired signaling of these neurons may contribute to PFC dysfunction.By sampling for behavioral alterations that map onto distinct symptom categories in schizophrenia, we show that dysfunction of PVI signaling in the PFC specifically produces deficits in the cognitive domain, but does not give rise to PFC-dependent correlates of negative or positive symptoms.Our results suggest that distinct aspects of the complex symptomatology of PFC dysfunction in schizophrenia can be attributed to specific prefrontal circuit elements.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom.

ABSTRACT
Dysfunction of parvalbumin (PV)-positive GABAergic interneurons (PVIs) within the prefrontal cortex (PFC) has been implicated in schizophrenia pathology. It is however unclear, how impaired signaling of these neurons may contribute to PFC dysfunction. To identify how PVIs contribute to PFC-dependent behaviors we inactivated PVIs in the PFC in mice using region- and cell-type-selective expression of tetanus toxin light chain (TeLC) and compared the functional consequences of this manipulation with non-cell-type-selective perturbations of the same circuitry. By sampling for behavioral alterations that map onto distinct symptom categories in schizophrenia, we show that dysfunction of PVI signaling in the PFC specifically produces deficits in the cognitive domain, but does not give rise to PFC-dependent correlates of negative or positive symptoms. Our results suggest that distinct aspects of the complex symptomatology of PFC dysfunction in schizophrenia can be attributed to specific prefrontal circuit elements.

No MeSH data available.


Related in: MedlinePlus

Cell-type-selective and general inactivation in the prefrontal cortex.(A) Injection of AAV-FLEX-TeLC into the PFC selectively blocks synaptic transmission in PVIs (grey shade in circuit cartoon) by cleaving VAMP2. Transmission in all other neurons remains intact. (B) Injection of ibotenic acid into the PFC causes general disruption of neuronal circuitry (grey shade). (C) Schematic of AAV spread in the mPFC of AAV-FLEX-TeLC-injected PV-Cre animals showing minimum (all animals >50% infected PVIs) and maximum (>50% infected PVIs only in most affected animals) infection area. (D) Immunohistochemistry illustrating co-localization of TeLC-GFP and PV in the mPFC (E), Schematic showing minimum (common to all animals) and maximum (in most affected animals) extent of ibotenic acid lesion in the mPFC. (F) Percentage of TeLC-GFP-expressing PVIs in subregions of the PFC. (G) Quantification of VAMP2 immunofluorescence intensity shows a substantial reduction in GFP-TeLC+/vGAT+ puncta in PFC-PV-TeLC animals compared with GFP+/vGAT+ puncta in PFC-PV-GFP animals. (H) Percentage of lesioned area in subfields of the PFC after ibotenic acid injection. PrL Prelimbic cortex; IL Infralimbic cortex; M2 Secondary motor cortex; CgL Cingulate; MO Medial orbital cortex. Scale bar in D = 20 µm. Data are mean ± s.e.m. ***p < 0.001.
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f1: Cell-type-selective and general inactivation in the prefrontal cortex.(A) Injection of AAV-FLEX-TeLC into the PFC selectively blocks synaptic transmission in PVIs (grey shade in circuit cartoon) by cleaving VAMP2. Transmission in all other neurons remains intact. (B) Injection of ibotenic acid into the PFC causes general disruption of neuronal circuitry (grey shade). (C) Schematic of AAV spread in the mPFC of AAV-FLEX-TeLC-injected PV-Cre animals showing minimum (all animals >50% infected PVIs) and maximum (>50% infected PVIs only in most affected animals) infection area. (D) Immunohistochemistry illustrating co-localization of TeLC-GFP and PV in the mPFC (E), Schematic showing minimum (common to all animals) and maximum (in most affected animals) extent of ibotenic acid lesion in the mPFC. (F) Percentage of TeLC-GFP-expressing PVIs in subregions of the PFC. (G) Quantification of VAMP2 immunofluorescence intensity shows a substantial reduction in GFP-TeLC+/vGAT+ puncta in PFC-PV-TeLC animals compared with GFP+/vGAT+ puncta in PFC-PV-GFP animals. (H) Percentage of lesioned area in subfields of the PFC after ibotenic acid injection. PrL Prelimbic cortex; IL Infralimbic cortex; M2 Secondary motor cortex; CgL Cingulate; MO Medial orbital cortex. Scale bar in D = 20 µm. Data are mean ± s.e.m. ***p < 0.001.

Mentions: We made stereotaxic injections of adeno-associated viruses carrying a GFP-tagged TeLC (or GFP alone as control, Fig. S1) reading frame inverted (3’ to 5’) in a flip-excision cassette (AAV-FLEX-TeLC and AAV-FLEX-GFP)26 into the PFC of PV-Cre knock-in mice27. As Cre-recombinase is required to flip the reading frame into the correct orientation, transcription of TeLC can only occur in PVIs26. Once expressed, TeLC efficiently stops transmitter release by cleaving VAMP2, a protein required for synaptic vesicle docking26 (Fig. 1A). Bilateral infusions of AAV-FLEX-TeLC resulted in expression of TeLC in over 75% of PVIs in prelimbic and infralimbic regions of the PFC (Fig. 1C,D,F). Additionally, TeLC expression was found in the cingulate and medial orbital cortices, demonstrating functional removal of PVIs across an area of mouse PFC thought to integrate functions of the dorsolateral, medial and orbital PFC in humans282930. Transgene-expression in PV-negative cells was scarce (4.3%) and likely includes PVIs containing PV levels below detection threshold. Similar results were obtained for control AAV-FLEX-GFP injections (PFC-PV-GFP mice, data not shown). As expected, immunoreactivity for VAMP2 was strongly reduced in TeLC-positive terminals of PFC-PV-TeLC mice when compared with GFP-positive terminals of PFC-PV-GFP mice (p < 0.0001; t = 22.2; n = 4 animals per group; Fig. 1G). The residual VAMP2 immunoreactivity is likely due to low affinity recognition of VAMP2 cleavage products by the antibody31. However, using the same AAV-FLEX-TeLC we have previously shown that transmission of hippocampal PVIs was fully abolished 10 days after virus injection despite residual VAMP2 immunoreactivity26. In principle, loss of PVI-mediated inhibition could induce hyper-activity in pyramidal cells and induce ictal discharges in the PFC, which in turn could complicate the interpretation of behavioral data. However, local field potential (LFP) recordings from PFC showed no indication of enhanced synchronous activity in PFC-PV-TeLC mice. PFC-PV-TeLC and PFC-PV-GFP mice displayed similar absolute power at different spectral frequency bands (Fig. S2). In a second set of experiments we also made non-cell-type-specific PFC lesions, which have previously been used to investigate the behavioral role of the PFC, by injection of the fiber-sparing neurotoxin ibotenic acid323334353637 (or saline as control; PFC-Lesion and PFC-Saline mice; Fig. 1B,E,H). We reasoned that this approach would confirm the PFC-dependence of our behavioral tests and that qualitative comparison of the behavioral deficits between PV-cell-selective and non-cell-type-selective circuit lesions would allow us to dissociate general PFC functions from those that specifically involve PVIs. To produce perturbations of comparable location and extent we titrated ibotenic acid injections according to viral spread.


Parvalbumin-positive interneurons of the prefrontal cortex support working memory and cognitive flexibility.

Murray AJ, Woloszynowska-Fraser MU, Ansel-Bollepalli L, Cole KL, Foggetti A, Crouch B, Riedel G, Wulff P - Sci Rep (2015)

Cell-type-selective and general inactivation in the prefrontal cortex.(A) Injection of AAV-FLEX-TeLC into the PFC selectively blocks synaptic transmission in PVIs (grey shade in circuit cartoon) by cleaving VAMP2. Transmission in all other neurons remains intact. (B) Injection of ibotenic acid into the PFC causes general disruption of neuronal circuitry (grey shade). (C) Schematic of AAV spread in the mPFC of AAV-FLEX-TeLC-injected PV-Cre animals showing minimum (all animals >50% infected PVIs) and maximum (>50% infected PVIs only in most affected animals) infection area. (D) Immunohistochemistry illustrating co-localization of TeLC-GFP and PV in the mPFC (E), Schematic showing minimum (common to all animals) and maximum (in most affected animals) extent of ibotenic acid lesion in the mPFC. (F) Percentage of TeLC-GFP-expressing PVIs in subregions of the PFC. (G) Quantification of VAMP2 immunofluorescence intensity shows a substantial reduction in GFP-TeLC+/vGAT+ puncta in PFC-PV-TeLC animals compared with GFP+/vGAT+ puncta in PFC-PV-GFP animals. (H) Percentage of lesioned area in subfields of the PFC after ibotenic acid injection. PrL Prelimbic cortex; IL Infralimbic cortex; M2 Secondary motor cortex; CgL Cingulate; MO Medial orbital cortex. Scale bar in D = 20 µm. Data are mean ± s.e.m. ***p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660359&req=5

f1: Cell-type-selective and general inactivation in the prefrontal cortex.(A) Injection of AAV-FLEX-TeLC into the PFC selectively blocks synaptic transmission in PVIs (grey shade in circuit cartoon) by cleaving VAMP2. Transmission in all other neurons remains intact. (B) Injection of ibotenic acid into the PFC causes general disruption of neuronal circuitry (grey shade). (C) Schematic of AAV spread in the mPFC of AAV-FLEX-TeLC-injected PV-Cre animals showing minimum (all animals >50% infected PVIs) and maximum (>50% infected PVIs only in most affected animals) infection area. (D) Immunohistochemistry illustrating co-localization of TeLC-GFP and PV in the mPFC (E), Schematic showing minimum (common to all animals) and maximum (in most affected animals) extent of ibotenic acid lesion in the mPFC. (F) Percentage of TeLC-GFP-expressing PVIs in subregions of the PFC. (G) Quantification of VAMP2 immunofluorescence intensity shows a substantial reduction in GFP-TeLC+/vGAT+ puncta in PFC-PV-TeLC animals compared with GFP+/vGAT+ puncta in PFC-PV-GFP animals. (H) Percentage of lesioned area in subfields of the PFC after ibotenic acid injection. PrL Prelimbic cortex; IL Infralimbic cortex; M2 Secondary motor cortex; CgL Cingulate; MO Medial orbital cortex. Scale bar in D = 20 µm. Data are mean ± s.e.m. ***p < 0.001.
Mentions: We made stereotaxic injections of adeno-associated viruses carrying a GFP-tagged TeLC (or GFP alone as control, Fig. S1) reading frame inverted (3’ to 5’) in a flip-excision cassette (AAV-FLEX-TeLC and AAV-FLEX-GFP)26 into the PFC of PV-Cre knock-in mice27. As Cre-recombinase is required to flip the reading frame into the correct orientation, transcription of TeLC can only occur in PVIs26. Once expressed, TeLC efficiently stops transmitter release by cleaving VAMP2, a protein required for synaptic vesicle docking26 (Fig. 1A). Bilateral infusions of AAV-FLEX-TeLC resulted in expression of TeLC in over 75% of PVIs in prelimbic and infralimbic regions of the PFC (Fig. 1C,D,F). Additionally, TeLC expression was found in the cingulate and medial orbital cortices, demonstrating functional removal of PVIs across an area of mouse PFC thought to integrate functions of the dorsolateral, medial and orbital PFC in humans282930. Transgene-expression in PV-negative cells was scarce (4.3%) and likely includes PVIs containing PV levels below detection threshold. Similar results were obtained for control AAV-FLEX-GFP injections (PFC-PV-GFP mice, data not shown). As expected, immunoreactivity for VAMP2 was strongly reduced in TeLC-positive terminals of PFC-PV-TeLC mice when compared with GFP-positive terminals of PFC-PV-GFP mice (p < 0.0001; t = 22.2; n = 4 animals per group; Fig. 1G). The residual VAMP2 immunoreactivity is likely due to low affinity recognition of VAMP2 cleavage products by the antibody31. However, using the same AAV-FLEX-TeLC we have previously shown that transmission of hippocampal PVIs was fully abolished 10 days after virus injection despite residual VAMP2 immunoreactivity26. In principle, loss of PVI-mediated inhibition could induce hyper-activity in pyramidal cells and induce ictal discharges in the PFC, which in turn could complicate the interpretation of behavioral data. However, local field potential (LFP) recordings from PFC showed no indication of enhanced synchronous activity in PFC-PV-TeLC mice. PFC-PV-TeLC and PFC-PV-GFP mice displayed similar absolute power at different spectral frequency bands (Fig. S2). In a second set of experiments we also made non-cell-type-specific PFC lesions, which have previously been used to investigate the behavioral role of the PFC, by injection of the fiber-sparing neurotoxin ibotenic acid323334353637 (or saline as control; PFC-Lesion and PFC-Saline mice; Fig. 1B,E,H). We reasoned that this approach would confirm the PFC-dependence of our behavioral tests and that qualitative comparison of the behavioral deficits between PV-cell-selective and non-cell-type-selective circuit lesions would allow us to dissociate general PFC functions from those that specifically involve PVIs. To produce perturbations of comparable location and extent we titrated ibotenic acid injections according to viral spread.

Bottom Line: It is however unclear, how impaired signaling of these neurons may contribute to PFC dysfunction.By sampling for behavioral alterations that map onto distinct symptom categories in schizophrenia, we show that dysfunction of PVI signaling in the PFC specifically produces deficits in the cognitive domain, but does not give rise to PFC-dependent correlates of negative or positive symptoms.Our results suggest that distinct aspects of the complex symptomatology of PFC dysfunction in schizophrenia can be attributed to specific prefrontal circuit elements.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom.

ABSTRACT
Dysfunction of parvalbumin (PV)-positive GABAergic interneurons (PVIs) within the prefrontal cortex (PFC) has been implicated in schizophrenia pathology. It is however unclear, how impaired signaling of these neurons may contribute to PFC dysfunction. To identify how PVIs contribute to PFC-dependent behaviors we inactivated PVIs in the PFC in mice using region- and cell-type-selective expression of tetanus toxin light chain (TeLC) and compared the functional consequences of this manipulation with non-cell-type-selective perturbations of the same circuitry. By sampling for behavioral alterations that map onto distinct symptom categories in schizophrenia, we show that dysfunction of PVI signaling in the PFC specifically produces deficits in the cognitive domain, but does not give rise to PFC-dependent correlates of negative or positive symptoms. Our results suggest that distinct aspects of the complex symptomatology of PFC dysfunction in schizophrenia can be attributed to specific prefrontal circuit elements.

No MeSH data available.


Related in: MedlinePlus