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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 anterior segment morphology.OCT images of the anterior segment and retina assessed for morphological changes and the amount of light reaching the retina (A, B, D & E). None of the anterior components of the eye are different between mutant mice and littermate controls at 5 (VAChTSix3-Cre-flox/flox, n = 6; control VAChTflox/flox, n = 12), or at 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). Images of the anterior segment have been combined with images of the retina. NR, neural retina; RPE, retinal pigment epithelium. (C, F) Central cornea thickness (CCT), anterior chamber diameter (ACD), anterior chamber width (ACW), pupil diameter (PD) and ratio of pupil diameter: anterior chamber depth (PD:ACW) did not differ between VAChTSix3-Cre-flox/flox and VAChTflox/flox mice at 5 or 12 months, respectively.
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pone.0133989.g011: Characterization of anterior segment morphology.OCT images of the anterior segment and retina assessed for morphological changes and the amount of light reaching the retina (A, B, D & E). None of the anterior components of the eye are different between mutant mice and littermate controls at 5 (VAChTSix3-Cre-flox/flox, n = 6; control VAChTflox/flox, n = 12), or at 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). Images of the anterior segment have been combined with images of the retina. NR, neural retina; RPE, retinal pigment epithelium. (C, F) Central cornea thickness (CCT), anterior chamber diameter (ACD), anterior chamber width (ACW), pupil diameter (PD) and ratio of pupil diameter: anterior chamber depth (PD:ACW) did not differ between VAChTSix3-Cre-flox/flox and VAChTflox/flox mice at 5 or 12 months, respectively.

Mentions: Three-dimensional in vivo imaging of the anterior segment (cornea, lens, iris, and anterior chamber) by OCT reveals no anterior obstructions or abnormalities in VAChTSix3-Cre-flox/flox mice compared to littermate controls, which could impede incipient light from reaching the retina and confound any assessment of principal ERG components (Fig 11A–11D). In addition, no evidence of micropthalmia, anophthalmy, angle closure or cornea or lens opacity that would obstruct light from reaching the retina was found. Central cornea thickness, anterior chamber angle, anterior chamber depth, and thickness of the anterior and posterior retina were quantified using a digiter caliper tool. VAChTSix3-Cre-flox/flox mice show no significant differences from littermate controls in any of these measures taken and at either age (Fig 11E and 11F). Additionally, intraocular pressure (IOP) was assessed to rule out elevated IOP as a contributing factor to any structural aberration, as elevated intraocular pressure (IOP) results in apoptosis-induced retinal ganglion cell death [49]. The IOP (mmHg) of VAChTSix3-Cre-flox/flox mice is not significantly different from littermate controls at either 5 (VAChTflox/flox 8.45 ± 0.42; VAChTSix3-Cre-flox/flox 8.64 ± 0.42) or 12 months of age (VAChTflox/flox 8.07 ± 0.37; VAChTSix3-Cre-flox/flox 8.62 ± 0.19).


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 anterior segment morphology.OCT images of the anterior segment and retina assessed for morphological changes and the amount of light reaching the retina (A, B, D & E). None of the anterior components of the eye are different between mutant mice and littermate controls at 5 (VAChTSix3-Cre-flox/flox, n = 6; control VAChTflox/flox, n = 12), or at 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). Images of the anterior segment have been combined with images of the retina. NR, neural retina; RPE, retinal pigment epithelium. (C, F) Central cornea thickness (CCT), anterior chamber diameter (ACD), anterior chamber width (ACW), pupil diameter (PD) and ratio of pupil diameter: anterior chamber depth (PD:ACW) did not differ between VAChTSix3-Cre-flox/flox and VAChTflox/flox mice at 5 or 12 months, respectively.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4520552&req=5

pone.0133989.g011: Characterization of anterior segment morphology.OCT images of the anterior segment and retina assessed for morphological changes and the amount of light reaching the retina (A, B, D & E). None of the anterior components of the eye are different between mutant mice and littermate controls at 5 (VAChTSix3-Cre-flox/flox, n = 6; control VAChTflox/flox, n = 12), or at 12 months of age (VAChTSix3-Cre-flox/flox, n = 5; control, n = 5). Images of the anterior segment have been combined with images of the retina. NR, neural retina; RPE, retinal pigment epithelium. (C, F) Central cornea thickness (CCT), anterior chamber diameter (ACD), anterior chamber width (ACW), pupil diameter (PD) and ratio of pupil diameter: anterior chamber depth (PD:ACW) did not differ between VAChTSix3-Cre-flox/flox and VAChTflox/flox mice at 5 or 12 months, respectively.
Mentions: Three-dimensional in vivo imaging of the anterior segment (cornea, lens, iris, and anterior chamber) by OCT reveals no anterior obstructions or abnormalities in VAChTSix3-Cre-flox/flox mice compared to littermate controls, which could impede incipient light from reaching the retina and confound any assessment of principal ERG components (Fig 11A–11D). In addition, no evidence of micropthalmia, anophthalmy, angle closure or cornea or lens opacity that would obstruct light from reaching the retina was found. Central cornea thickness, anterior chamber angle, anterior chamber depth, and thickness of the anterior and posterior retina were quantified using a digiter caliper tool. VAChTSix3-Cre-flox/flox mice show no significant differences from littermate controls in any of these measures taken and at either age (Fig 11E and 11F). Additionally, intraocular pressure (IOP) was assessed to rule out elevated IOP as a contributing factor to any structural aberration, as elevated intraocular pressure (IOP) results in apoptosis-induced retinal ganglion cell death [49]. The IOP (mmHg) of VAChTSix3-Cre-flox/flox mice is not significantly different from littermate controls at either 5 (VAChTflox/flox 8.45 ± 0.42; VAChTSix3-Cre-flox/flox 8.64 ± 0.42) or 12 months of age (VAChTflox/flox 8.07 ± 0.37; VAChTSix3-Cre-flox/flox 8.62 ± 0.19).

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