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Whole-Retina Reduced Electrophysiological Activity in Mice Bearing Retina-Specific Deletion of Vesicular Acetylcholine Transporter.

Bedore J, Martyn AC, Li AK, Dolinar EA, McDonald IS, Coupland SG, Prado VF, Prado MA, Hill KA - PLoS ONE (2015)

Bottom Line: One of the unanswered questions is how acetylcholine contributes to the functional capacity of mature retinal circuits.Reduced a-wave amplitude was proportional to the reduction in b-wave amplitude and not associated with altered a-wave 10%-90% rise time or inner and outer segment thicknesses.Reduced amplitude across the electroretinogram wave form does not suggest dysfunction in specific retinal cell types and could reflect underlying changes in the retinal and/or extraretinal microenvironment.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The University of Western Ontario, London, Ontario, Canada N6A 5B7.

ABSTRACT

Background: Despite rigorous characterization of the role of acetylcholine in retinal development, long-term effects of its absence as a neurotransmitter are unknown. One of the unanswered questions is how acetylcholine contributes to the functional capacity of mature retinal circuits. The current study investigates the effects of disrupting cholinergic signalling in mice, through deletion of vesicular acetylcholine transporter (VAChT) in the developing retina, pigmented epithelium, optic nerve and optic stalk, on electrophysiology and structure of the mature retina.

Methods & results: A combination of electroretinography, optical coherence tomography imaging and histological evaluation assessed retinal integrity in mice bearing retina- targeted (embryonic day 12.5) deletion of VAChT (VAChTSix3-Cre-flox/flox) and littermate controls at 5 and 12 months of age. VAChTSix3-Cre-flox/flox mice did not show any gross changes in nuclear layer cellularity or synaptic layer thickness. However, VAChTSix3-Cre-flox/flox mice showed reduced electrophysiological response of the retina to light stimulus under scotopic conditions at 5 and 12 months of age, including reduced a-wave, b-wave, and oscillatory potential (OP) amplitudes and decreased OP peak power and total energy. Reduced a-wave amplitude was proportional to the reduction in b-wave amplitude and not associated with altered a-wave 10%-90% rise time or inner and outer segment thicknesses.

Significance: This study used a novel genetic model in the first examination of function and structure of the mature mouse retina with disruption of cholinergic signalling. Reduced amplitude across the electroretinogram wave form does not suggest dysfunction in specific retinal cell types and could reflect underlying changes in the retinal and/or extraretinal microenvironment. Our findings suggest that release of acetylcholine by VAChT is essential for the normal electrophysiological response of the mature mouse retina.

No MeSH data available.


Related in: MedlinePlus

Characterization of retinal layer morphology.(A, B, E & F) Representative images of Hematoxylin and eosin (H&E) stained 6 μ cross sections of retinas from VAChTflox/flox control and VAChTSix3-Cre-flox/flox retinas at (A-B) 5 and (E-F) 12 months of age showing retinal layers. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; OS, outer segment; RPE, retinal pigment epithelium. Retinal layer morphology was assessed in VAChTSix3-Cre-flox/flox mice at (C, D) 5 (VAChTSix3-Cre-flox/flox, n = 5; littermate control VAChTflox/flox, n = 5) and (G-H) 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; littermate control, n = 5). INL and ONL cell counts are normal in VAChTSix3-Cre-flox/flox mice at 5 and 12 months of age (C, G). Measurements of synaptic layer thickness of the IPL and OPL show no differences between VAChTSix3-Cre-flox/flox and control mice (D, H). Scale bar represents 50 μm for all images.
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pone.0133989.g010: Characterization of retinal layer morphology.(A, B, E & F) Representative images of Hematoxylin and eosin (H&E) stained 6 μ cross sections of retinas from VAChTflox/flox control and VAChTSix3-Cre-flox/flox retinas at (A-B) 5 and (E-F) 12 months of age showing retinal layers. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; OS, outer segment; RPE, retinal pigment epithelium. Retinal layer morphology was assessed in VAChTSix3-Cre-flox/flox mice at (C, D) 5 (VAChTSix3-Cre-flox/flox, n = 5; littermate control VAChTflox/flox, n = 5) and (G-H) 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; littermate control, n = 5). INL and ONL cell counts are normal in VAChTSix3-Cre-flox/flox mice at 5 and 12 months of age (C, G). Measurements of synaptic layer thickness of the IPL and OPL show no differences between VAChTSix3-Cre-flox/flox and control mice (D, H). Scale bar represents 50 μm for all images.

Mentions: To investigate whether structural changes resulted from retina-specific deletion of VAChT, VAChTSix3-Cre-flox/flox and littermate control retinas were assessed histologically at 5 and 12 months of age (Fig 10). Cellularity of the inner and outer nuclear layer is normal in VAChTSix3-Cre-flox/flox mice relative to littermate controls at 5 (Fig 10A) and 12 months of age (Fig 10B). Synaptic layer thicknesses of the outer plexiform layer and inner plexiform layer are not different between VAChTSix3-Cre-flox/flox and littermate control mice (Fig 10C and 10D). The retinal IS:OS ratio did not differ significantly with age or genotype [1.80 ± 0.04 and 1.72 ± 0.04 for 5- and 12-month-old VAChTSix3-Cre-flox/flox mice and 1.69 ± 0.04 and 1.74 ± 0.06 for 5- and 12-month-old littermate control mice (mean+/-SEM)].


Whole-Retina Reduced Electrophysiological Activity in Mice Bearing Retina-Specific Deletion of Vesicular Acetylcholine Transporter.

Bedore J, Martyn AC, Li AK, Dolinar EA, McDonald IS, Coupland SG, Prado VF, Prado MA, Hill KA - PLoS ONE (2015)

Characterization of retinal layer morphology.(A, B, E & F) Representative images of Hematoxylin and eosin (H&E) stained 6 μ cross sections of retinas from VAChTflox/flox control and VAChTSix3-Cre-flox/flox retinas at (A-B) 5 and (E-F) 12 months of age showing retinal layers. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; OS, outer segment; RPE, retinal pigment epithelium. Retinal layer morphology was assessed in VAChTSix3-Cre-flox/flox mice at (C, D) 5 (VAChTSix3-Cre-flox/flox, n = 5; littermate control VAChTflox/flox, n = 5) and (G-H) 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; littermate control, n = 5). INL and ONL cell counts are normal in VAChTSix3-Cre-flox/flox mice at 5 and 12 months of age (C, G). Measurements of synaptic layer thickness of the IPL and OPL show no differences between VAChTSix3-Cre-flox/flox and control mice (D, H). Scale bar represents 50 μm for all images.
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pone.0133989.g010: Characterization of retinal layer morphology.(A, B, E & F) Representative images of Hematoxylin and eosin (H&E) stained 6 μ cross sections of retinas from VAChTflox/flox control and VAChTSix3-Cre-flox/flox retinas at (A-B) 5 and (E-F) 12 months of age showing retinal layers. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; OS, outer segment; RPE, retinal pigment epithelium. Retinal layer morphology was assessed in VAChTSix3-Cre-flox/flox mice at (C, D) 5 (VAChTSix3-Cre-flox/flox, n = 5; littermate control VAChTflox/flox, n = 5) and (G-H) 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; littermate control, n = 5). INL and ONL cell counts are normal in VAChTSix3-Cre-flox/flox mice at 5 and 12 months of age (C, G). Measurements of synaptic layer thickness of the IPL and OPL show no differences between VAChTSix3-Cre-flox/flox and control mice (D, H). Scale bar represents 50 μm for all images.
Mentions: To investigate whether structural changes resulted from retina-specific deletion of VAChT, VAChTSix3-Cre-flox/flox and littermate control retinas were assessed histologically at 5 and 12 months of age (Fig 10). Cellularity of the inner and outer nuclear layer is normal in VAChTSix3-Cre-flox/flox mice relative to littermate controls at 5 (Fig 10A) and 12 months of age (Fig 10B). Synaptic layer thicknesses of the outer plexiform layer and inner plexiform layer are not different between VAChTSix3-Cre-flox/flox and littermate control mice (Fig 10C and 10D). The retinal IS:OS ratio did not differ significantly with age or genotype [1.80 ± 0.04 and 1.72 ± 0.04 for 5- and 12-month-old VAChTSix3-Cre-flox/flox mice and 1.69 ± 0.04 and 1.74 ± 0.06 for 5- and 12-month-old littermate control mice (mean+/-SEM)].

Bottom Line: One of the unanswered questions is how acetylcholine contributes to the functional capacity of mature retinal circuits.Reduced a-wave amplitude was proportional to the reduction in b-wave amplitude and not associated with altered a-wave 10%-90% rise time or inner and outer segment thicknesses.Reduced amplitude across the electroretinogram wave form does not suggest dysfunction in specific retinal cell types and could reflect underlying changes in the retinal and/or extraretinal microenvironment.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The University of Western Ontario, London, Ontario, Canada N6A 5B7.

ABSTRACT

Background: Despite rigorous characterization of the role of acetylcholine in retinal development, long-term effects of its absence as a neurotransmitter are unknown. One of the unanswered questions is how acetylcholine contributes to the functional capacity of mature retinal circuits. The current study investigates the effects of disrupting cholinergic signalling in mice, through deletion of vesicular acetylcholine transporter (VAChT) in the developing retina, pigmented epithelium, optic nerve and optic stalk, on electrophysiology and structure of the mature retina.

Methods & results: A combination of electroretinography, optical coherence tomography imaging and histological evaluation assessed retinal integrity in mice bearing retina- targeted (embryonic day 12.5) deletion of VAChT (VAChTSix3-Cre-flox/flox) and littermate controls at 5 and 12 months of age. VAChTSix3-Cre-flox/flox mice did not show any gross changes in nuclear layer cellularity or synaptic layer thickness. However, VAChTSix3-Cre-flox/flox mice showed reduced electrophysiological response of the retina to light stimulus under scotopic conditions at 5 and 12 months of age, including reduced a-wave, b-wave, and oscillatory potential (OP) amplitudes and decreased OP peak power and total energy. Reduced a-wave amplitude was proportional to the reduction in b-wave amplitude and not associated with altered a-wave 10%-90% rise time or inner and outer segment thicknesses.

Significance: This study used a novel genetic model in the first examination of function and structure of the mature mouse retina with disruption of cholinergic signalling. Reduced amplitude across the electroretinogram wave form does not suggest dysfunction in specific retinal cell types and could reflect underlying changes in the retinal and/or extraretinal microenvironment. Our findings suggest that release of acetylcholine by VAChT is essential for the normal electrophysiological response of the mature mouse retina.

No MeSH data available.


Related in: MedlinePlus