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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

Assessment of oscillatory potential implicit times.Implicit times of OP peaks assessed in VAChTSix3-Cre-flox/flox mice (open circles) and littermate controls (VAChTflox/flox, closed squares) at either 5 (VAChTSix3-Cre-flox/flox, n = 7; control, n = 12) or 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). The initial implicit time, measures time from stimulus onset to the peak of the first OP, is not different between genotypes at (A) 5 months of age, but is significantly reduced in VAChTSix3-Cre-flox/flox mice at (B) 12 months of age. The implicit times of OP3 (C-D), OP4 (E-F), and OP5 (G-H) are not different between genotypes at either age. δ, P < 0.05; α, P < 0.0001 versus control mice.
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pone.0133989.g009: Assessment of oscillatory potential implicit times.Implicit times of OP peaks assessed in VAChTSix3-Cre-flox/flox mice (open circles) and littermate controls (VAChTflox/flox, closed squares) at either 5 (VAChTSix3-Cre-flox/flox, n = 7; control, n = 12) or 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). The initial implicit time, measures time from stimulus onset to the peak of the first OP, is not different between genotypes at (A) 5 months of age, but is significantly reduced in VAChTSix3-Cre-flox/flox mice at (B) 12 months of age. The implicit times of OP3 (C-D), OP4 (E-F), and OP5 (G-H) are not different between genotypes at either age. δ, P < 0.05; α, P < 0.0001 versus control mice.

Mentions: Upon comparing individual OP peaks in the time-domain (Fig 8A–8H) all four OPs are significantly reduced in VAChTSix3-Cre-flox/flox retinas at both ages, OP2 (P < 0.0001), OP3 (P < 0.0001), OP4 (P < 0.0001), OP5 (P<0.01). This is also reflected by decreased summed OP amplitude in VAChTSix3-Cre-flox/flox retinas in comparison to littermate control mice at both ages (Fig 8I and 8J; P < 0.0001). At 5 months of age, there are no significant differences in OP1 implicit time or any OP interpeak intervals (Fig 9A, 9C, 9E and 9G). However, at 12 months of age, the implicit time of OP1 is significantly shorter in VAChTSix3-Cre-flox/flox mice (P<0.0001). The implicit times of all subsequent OPs are not significantly different between genotypes at this age (Fig 9D, 9F and 9H). No significant interactions between age and genotype, indicating worsening or recovery of deficits in VAChTSix3-Cre-flox/flox retinas were found for any of the ERG measures analyzed.


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)

Assessment of oscillatory potential implicit times.Implicit times of OP peaks assessed in VAChTSix3-Cre-flox/flox mice (open circles) and littermate controls (VAChTflox/flox, closed squares) at either 5 (VAChTSix3-Cre-flox/flox, n = 7; control, n = 12) or 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). The initial implicit time, measures time from stimulus onset to the peak of the first OP, is not different between genotypes at (A) 5 months of age, but is significantly reduced in VAChTSix3-Cre-flox/flox mice at (B) 12 months of age. The implicit times of OP3 (C-D), OP4 (E-F), and OP5 (G-H) are not different between genotypes at either age. δ, P < 0.05; α, P < 0.0001 versus control mice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520552&req=5

pone.0133989.g009: Assessment of oscillatory potential implicit times.Implicit times of OP peaks assessed in VAChTSix3-Cre-flox/flox mice (open circles) and littermate controls (VAChTflox/flox, closed squares) at either 5 (VAChTSix3-Cre-flox/flox, n = 7; control, n = 12) or 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). The initial implicit time, measures time from stimulus onset to the peak of the first OP, is not different between genotypes at (A) 5 months of age, but is significantly reduced in VAChTSix3-Cre-flox/flox mice at (B) 12 months of age. The implicit times of OP3 (C-D), OP4 (E-F), and OP5 (G-H) are not different between genotypes at either age. δ, P < 0.05; α, P < 0.0001 versus control mice.
Mentions: Upon comparing individual OP peaks in the time-domain (Fig 8A–8H) all four OPs are significantly reduced in VAChTSix3-Cre-flox/flox retinas at both ages, OP2 (P < 0.0001), OP3 (P < 0.0001), OP4 (P < 0.0001), OP5 (P<0.01). This is also reflected by decreased summed OP amplitude in VAChTSix3-Cre-flox/flox retinas in comparison to littermate control mice at both ages (Fig 8I and 8J; P < 0.0001). At 5 months of age, there are no significant differences in OP1 implicit time or any OP interpeak intervals (Fig 9A, 9C, 9E and 9G). However, at 12 months of age, the implicit time of OP1 is significantly shorter in VAChTSix3-Cre-flox/flox mice (P<0.0001). The implicit times of all subsequent OPs are not significantly different between genotypes at this age (Fig 9D, 9F and 9H). No significant interactions between age and genotype, indicating worsening or recovery of deficits in VAChTSix3-Cre-flox/flox retinas were found for any of the ERG measures analyzed.

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