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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 electrophysiology under scotopic conditions.Representative scotopic ERG traces for VAChTSix3-Cre-flox/flox and VAChTflox/flox littermate control mice at (A) 5 and (B) 12 months of age at eleven light stimuli of increasing strength. ERG waveforms assessed in response to 11 light stimuli of increasing luminance (0.001 to 25 cd˖s/m2). Waveforms are arranged from lowest stimulus luminance (top) to highest (bottom). Amplitudes of the a-wave (squares) and b-wave (circles) are reduced in VAChTSix3-Cre-flox/flox retinas relative to littermate controls, whereas implicit times of the a- and b-waves are unaffected by the loss of VAChT.; the stimulus onset is indicated by a sideways cross mark.
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pone.0133989.g003: Characterization of retinal electrophysiology under scotopic conditions.Representative scotopic ERG traces for VAChTSix3-Cre-flox/flox and VAChTflox/flox littermate control mice at (A) 5 and (B) 12 months of age at eleven light stimuli of increasing strength. ERG waveforms assessed in response to 11 light stimuli of increasing luminance (0.001 to 25 cd˖s/m2). Waveforms are arranged from lowest stimulus luminance (top) to highest (bottom). Amplitudes of the a-wave (squares) and b-wave (circles) are reduced in VAChTSix3-Cre-flox/flox retinas relative to littermate controls, whereas implicit times of the a- and b-waves are unaffected by the loss of VAChT.; the stimulus onset is indicated by a sideways cross mark.

Mentions: VAChTSix3-Cre-flox/flox mice show reduced amplitude of three major components of the scotopic ERG (a-wave, b-wave and OPs) relative to littermate controls over scotopic adapted flash intensities stimulating rod and mixed rod-cone activity [38] at 5 and 12 months of age (Fig 3). VAChTSix3-Cre-flox/flox mice show reduced a-wave amplitude both at 5 months (Fig 4A;, P<0.001) and 12 months of age (Fig 4B; P<0.001). B-wave amplitude is also significantly decreased in VAChTSix3-Cre-flox/flox mice at 5 months of age (Fig 4C; P<0.0001) and 12 months of age (Fig 4D; P<0.0001). At 5 months of age, the magnitude of a-wave and b-wave reduction in VAChTSix3-Cre-flox/flox mice showed a strong correlation (Fig 4E; P<0.0001; r = 0.9007; r2 = 0.8113). At 12 months of age the magnitude of a- and b-wave reduction in VAChTSix3-Cre-flox/flox mice also showed a strong correlation (Fig 4F; P<0.01; r = 0.7642; r2 = 0.5839). A-wave implicit time is not significantly different from littermate control mice at either 5 or 12 months of age (Fig 4G and 4H). There are also no significant differences in b-wave implicit times between VAChTSix3-Cre-flox/flox and littermate controls at either 5 or 12 months of age (Fig 4I and 4J).


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 electrophysiology under scotopic conditions.Representative scotopic ERG traces for VAChTSix3-Cre-flox/flox and VAChTflox/flox littermate control mice at (A) 5 and (B) 12 months of age at eleven light stimuli of increasing strength. ERG waveforms assessed in response to 11 light stimuli of increasing luminance (0.001 to 25 cd˖s/m2). Waveforms are arranged from lowest stimulus luminance (top) to highest (bottom). Amplitudes of the a-wave (squares) and b-wave (circles) are reduced in VAChTSix3-Cre-flox/flox retinas relative to littermate controls, whereas implicit times of the a- and b-waves are unaffected by the loss of VAChT.; the stimulus onset is indicated by a sideways cross mark.
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Related In: Results  -  Collection

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pone.0133989.g003: Characterization of retinal electrophysiology under scotopic conditions.Representative scotopic ERG traces for VAChTSix3-Cre-flox/flox and VAChTflox/flox littermate control mice at (A) 5 and (B) 12 months of age at eleven light stimuli of increasing strength. ERG waveforms assessed in response to 11 light stimuli of increasing luminance (0.001 to 25 cd˖s/m2). Waveforms are arranged from lowest stimulus luminance (top) to highest (bottom). Amplitudes of the a-wave (squares) and b-wave (circles) are reduced in VAChTSix3-Cre-flox/flox retinas relative to littermate controls, whereas implicit times of the a- and b-waves are unaffected by the loss of VAChT.; the stimulus onset is indicated by a sideways cross mark.
Mentions: VAChTSix3-Cre-flox/flox mice show reduced amplitude of three major components of the scotopic ERG (a-wave, b-wave and OPs) relative to littermate controls over scotopic adapted flash intensities stimulating rod and mixed rod-cone activity [38] at 5 and 12 months of age (Fig 3). VAChTSix3-Cre-flox/flox mice show reduced a-wave amplitude both at 5 months (Fig 4A;, P<0.001) and 12 months of age (Fig 4B; P<0.001). B-wave amplitude is also significantly decreased in VAChTSix3-Cre-flox/flox mice at 5 months of age (Fig 4C; P<0.0001) and 12 months of age (Fig 4D; P<0.0001). At 5 months of age, the magnitude of a-wave and b-wave reduction in VAChTSix3-Cre-flox/flox mice showed a strong correlation (Fig 4E; P<0.0001; r = 0.9007; r2 = 0.8113). At 12 months of age the magnitude of a- and b-wave reduction in VAChTSix3-Cre-flox/flox mice also showed a strong correlation (Fig 4F; P<0.01; r = 0.7642; r2 = 0.5839). A-wave implicit time is not significantly different from littermate control mice at either 5 or 12 months of age (Fig 4G and 4H). There are also no significant differences in b-wave implicit times between VAChTSix3-Cre-flox/flox and littermate controls at either 5 or 12 months of age (Fig 4I and 4J).

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