Age-Related Changes in the Daily Rhythm of
Photoreceptor Functioning and Circuitry in a Melatonin-
Proficient Mouse Strain
Kenkichi Baba1, Francesca Mazzoni2, Sharon Owino1, Susana Contreras-Alcantara1, Enrica Strettoi2,
1Circadian Rhythms and Sleep Disorders Program, Neuroscience Institute, Department of Anatomy and Neurobiology, Morehouse School of Medicine, CNR, Pisa, Italy,
2Neuroscience Institute, Italian National Research Council, CNR, Pisa, Italy
Retinal melatonin is involved in the modulation of many important retinal functions. Our previous studies have shown that
the viability of photoreceptors and ganglion cells is reduced during aging in mice that lack melatonin receptor type 1. This
demonstrates that melatonin signaling is important for the survival of retinal neurons. In the present study, we investigate
the effects of aging on photoreceptor physiology and retinal organization in CH3-f+/+ mice, a melatonin proficient mouse
strain. Our data indicate that the amplitude of the a and b waves of the scotopic and photopic electroretinogram decreases
with age. Moreover, the daily rhythm in the amplitude of the a- and b- waves is lost during the aging process. Similarly, the
scotopic threshold response is significantly affected by aging, but only when it is measured during the night. Interestingly,
the changes observed in the ERGs are not paralleled by relevant changes in retinal morphological features, and
administration of exogenous melatonin does not affect the ERGs in C3H-f+/+at 12 months of age. This suggests that the
responsiveness of the photoreceptors to exogenous melatonin is reduced during aging.
Citation: Baba K, Mazzoni F, Owino S, Contreras-Alcantara S, Strettoi E, et al. (2012) Age-Related Changes in the Daily Rhythm of Photoreceptor Functioning and
Circuitry in a Melatonin-Proficient Mouse Strain. PLoS ONE 7(5): e37799. doi:10.1371/journal.pone.0037799
Editor: Martine Migaud, Institut National de la Recherche Agronomique-CNRS UMR6175, France
Received February 7, 2012; Accepted April 24, 2012; Published May 22, 2012
Copyright: ? 2012 Baba et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by National Institutes of Health Grants NS43459, EY28821, EY022216; 5S21MD000101, 5U54NS060659, S21MD000101, G12-
RR03034, the Georgia Research Alliance (to G.T.), and EY12654 (to E.S.). The funders had no role in study design, data collection and analysis, decision to publish,
or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist. Gianluca Tosini is a PLoS ONE editorial member. This does not alter the
authors’ adherence to all the PLoS One policies on sharing data and materials.
* E-mail: firstname.lastname@example.org
In the mammalian retina, melatonin is synthesized by
photoreceptors with high levels of melatonin at night and lower
levels during the day . Melatonin in the eye is believed to be
involved in the modulation of many important retinal functions;
for instance, it can modulate the electroretinogram response
(ERG, [2–5]), and administration of exogenous melatonin
increases light-induced photoreceptor degeneration . Melatonin
may also have protective effects on photoreceptors [4,7] and on
other cell types, such as ganglion cells . Recent studies have
implicated melatonin in the pathogenesis of age-related macular
degeneration (AMD). Yi et al.  reported that oral administra-
tion of melatonin (3 mg) may protect the retina and delay the
progression of AMD, while Rosen et al.  reported that
production of melatonin is decreased in AMD patients with
respect to age-matched controls, thus suggesting that a deficiency
in melatonin may play a role in the pathogenesis of AMD.
Melatonin acts via melatonin receptors that are found in many
retinal cells types . In particular, melatonin receptors
type 1(MT1) have been localized to the photoreceptor cells in
many species, including humans [4,11,12]; thus, this neurohor-
mone may play an important role in photoreceptor functions.
Previous studies have investigated the effect of aging on the
retinal structure and functioning in the mouse. Overall, the data
indicate that the amplitude of the ERG declines with age and that
these changes do not correlate with significant changes in the
morphology of the photoreceptor cells, at least until 12 months of
age (13, 14). However, it is important to note that these studies
were performed in C57BL/6 and Balb/c mice, which are
genetically deficient to synthesize melatonin in the pineal gland
and retina (15, 16) because they have a mutation in AANAT that
prevents the synthesis of appreciable amounts of melatonin (17).
Several studies have indicated that melatonin may delay the
neurodegenerative process of aging . Therefore, we investigate
the effects of aging on retinal functioning and organization in
C3H-f+/+ mice, a melatonin proficient mouse strain [15,16].
Effect of Aging on the Scotopic Electroretinogram (ERG)
and Scotopic Threshold Response (STR)
The scotopic ERG was recorded in mice of different ages (3, 6,
and 12 months) and at two different time points (ZT6 and ZT18).
As shown in Figures 1A through 1F, the amplitude of the a and b
waves at ZT6 and ZT18 steadily decreases with age. The
amplitude of the waves of younger mice (3 months) is significantly
higher than that observed in 6-month-old mice (Two-way
ANOVA, P,0.01 followed by Tukey tests, P,0.05). The
PLoS ONE | www.plosone.org1 May 2012 | Volume 7 | Issue 5 | e37799
amplitude of the a and b waves of 12-month-old mice was
significantly lower than that measured in 6-month-old mice (Two-
way ANOVA, P,0.01 followed by Tukey tests, P,0.05). No
further decrease in the amplitude of a and b waves was observed in
older mice (Two-way ANOVA, P.0.1, data not shown). The
diurnal rhythm in the amplitude of the a and b waves was present
in young mice (3 and 6 months, Two-way Anova, P,0.01; see
Figure 1A, 1B, 1D and 1E) but not in older mice (Figures 1C and
1F; Two-way ANOVA, P.0.1). We then investigated the STR for
the three different ages at ZT6 (Figure 2A) and at ZT18
(Figure 2B). As shown in Figure 2, no differences were observed
at ZT6 between the three age groups (Two-way ANOVA,
P.0.05); however, at ZT18, the STR for 3- and 6-month-old
mice became detectable at the light intensity of 24.60 log cd*s/m2
(t-tests, P,0.05), while the light response of 12-month-old mice
became detectable at 23.60 log cd*s/m2(t-test, P,0.05).
Effects of Aging on the Photopic ERG
The effects of aging on the photopic ERG were investigated
using a protocol similar to that used by Baba et al. . The ERGs
from C3H/f+/+mice at different ages (3, 6 and 12 months) were
recorded at ZT6 and ZT18 after 2.5, 5, 10, and 15 min of rod
saturating background light exposure. Our data indicate that the
amplitude of the b wave at ZT6 was not affected by age (Figure 3A,
Two-way ANOVA, P.0.05). whereas the amplitude of the b wave
at ZT 18 was significantly affected by age (Two-way ANOVA,
P.0.01 followed by Tukey tests, P,0.05). The amplitude of the b
wave of younger mice (3 months) at ZT18 was significantly higher
than that observed in 6- and 12-month-old mice (Two-way
ANOVA, P,0.01 followed by Tukey tests, P,0.05, Figure 3B).
Effects of Aging on Retinal Organization
We next investigated whether overall retinal organization and
connectivity were affected by aging. No major alterations in retinal
morphology were evident between retinas obtained from 3- and
Figure 1. Effect of aging on the scotopic ERG and its daily rhythm. The amplitude of the a wave (A–C) and b wave (D–F) of the scotopic ERG
steadily decreased during aging, and the daily rhythm in the a and b wave amplitude was only present in mice at 3 and 6 months (Two-way ANOVA,
P,0.001, followed by Tukey tests). No significant difference in the amplitude of the a and b waves was detected in 12-month-old mice (Two-way
ANOVA, P.0.1) White circles indicate the average amplitude at ZT6, and black circles indicate the average values at ZT18. Each point represents the
mean 6 SEM, where N=4–14 for each point. Figures G through I, show representative traces of the dark-adapted ERGs at ZT18 (black lines) and at
ZT6 (grey lines) for the different ages (G=3 months; H=6 months; I=12 months).
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org2 May 2012 | Volume 7 | Issue 5 | e37799
12-month-old mice (Figure 4). Cells belonging to all retinal classes,
including rods and cones, horizontal cells, rod and cone bipolar
cells, various types of amacrine cells, such as Tyroxine Hydrox-
ylase (TH) and calbindin positive amacrines, and ganglion cells, as
well as Muller glia and astrocytes, were visualized with specific
antibodies on vertical retinal sections and appeared normal in
morphology, pattern of stratification, and overall architecture,
conforming to the published literature . Synaptic markers,
namely bassoon, kinesin II, post-synaptic density protein 95
(PSD95), and synaptophysin, were normally distributed in the two
plexiform layers of both genotypes. Local signs of focal
rearrangements (i.e., formation of rosettes, a common finding in
retinal reorganization) or signs of glial reactivity in Muller cells,
microglia and astrocytes, which are frequently reported in a
variety of pathological mutants , were undetected in these
mice. The only evident feature at 1 year of age was the locally
irregular profile of the outer plexiform layer, which was
particularly visible when markers such as PSD95 or kinesin 2
and bassoon (labeling photoreceptor synaptic endings and ribbon
proteins, respectively) were used. These antibodies showed
immunopositive elements in the outer nuclear layer (i.e. panels C,
D and E of Figure 4), indicating a mislocation of the photoreceptor
endings and their synaptic machinery toward the outer retina. We
explain this finding as the beginning of the known process of
retraction of photoreceptor endings, paralleled by sprouting of
bipolar cell dendrites common in the retina of very old mice 
but starting at one year of age .
Effects of Administration of Exogenous Melatonin on the
We previously showed that administration of exogenous
melatonin (1 mg/kg i.p.) induces a significant increase in the
amplitudes of dark-adapted ERG in young mice; specifically,
injections of 1 mg/kg of melatonin at ZT 6 can increase the
amplitude of a and b waves in 3-month-old mice (P,0.01, Two-
way ANOVA, Figure 5A, D) . In this study, we tested whether
injections of exogenous melatonin could restore the ERG
amplitude to the levels of young mice by increasing the
concentration of melatonin (0.01, 0.1 and 1 mg/Kg). In 3-
month-old mice, injection of 1 and 0.1 mg/Kg of melatonin at the
dose increased the amplitude of the a and bwaves of the scotopic
ERG (Two-way ANOVA, P.0.05, followed by Tukey tests,
Figure 2. Effect of aging on the STR. (A) No differences were observed at ZT6 in the STR among young and old mice (t-tests, P.0.5 in all cases).
Black circles, white circles, and black triangles indicate 3-, 6-, and 12-month-old mice, respectively. Each point represents the mean 6 SEM, N=6–8 for
each point. (B) At ZT18 the STR significantly increased (24.60 log log cd*s/m2vs 23.60 log cd*s/m2n) in 12-month-old mice (t-tests, P,0.05). Figures
C through E show representative traces of the ERG at the different ages (C=3 months; D=6 months; E=12 months).
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org3 May 2012 | Volume 7 | Issue 5 | e37799
P,0.05, Figures 5A and 5D). No effect was observed with
administration of 0.01 mg/Kg (Two-way ANOVA, P,0.1). The
dose of 0.1 mg/kg did not have an effect on a and b wave
amplitude in 6-month-old mice (Two-way ANOVA, P.0.05,
Figures 5B and 5E). Injecting 1mg/kg of melatonin increased the
amplitude of the a wave (Two-way ANOVA p,0.05 followed by
Tukey tests, P,0.05, melatonin vs. control, Figures 5B and 5E)
and of the b wave (Two-way ANOVA P,0.01 followed by Tukey
tests, P,0.05, melatonin vs. control, Figures 5B and 5E) in 6-
month-old mice. However, it did not increase the amplitude of the
a and b waves in 12-month-old mice (Two-way ANOVA, P.0.1
melatonin vs. control, Figures C, F). Although melatonin admin-
istered to 6-month-old mice successfully recovered the amplitude
of the a -wave, it did not fully rescue the amplitude of the b wave
(3 months vs. 6 months; Two-way ANOVA p,0.05, followed by
Tukey tests, P,0.05). The same melatonin treatment increased
both a and b wave amplitudes in 3-month-old mice (a wave
p,0.05, b wave, Two-way ANOVA, p,0.01control vs. 0.1 mg/
The role played by melatonin and melatonin receptors in the
mammalian retina is not well defined. The lack of data is due to
the fact that the vast majority of mouse strains are genetically
deficient in synthesizing melatonin in the pineal gland and retina
[20–21], so very few studies have compared retinal physiology in
melatonin-proficient and melatonin-deficient mice. This situation
is further complicated by the fact that C57/BL6 and other strains
may produce a small amount of melatonin; therefore, we cannot
completely exclude that this small amount may somehow influence
the mouse physiology . In the present study, we investigated
the effect of aging on retinal function and morphology in a
melatonin proficient mouse strain (C3H-f+/+). Our data indicate
that the following: the amplitude of the a and b waves of dark-
adapted ERG decrease with age; the daily rhythm in the ERGs is
lost by the age of 12 months; the STR at ZT18 is significantly
affected by age; the amplitude of the photopic ERG and its daily
rhythm are also affected by age; the changes observed in the ERGs
are not paralleled by gross alterations in retinal general
morphology; and administration of exogenous melatonin affects
the ERGs in 12-month-old mice.
Age-related declines in retinal function have been reported for
mice [13–14] and for humans . Our data are in agreement
with previous reports and expand these results by showing that the
daily rhythm in the scotopic and photopic ERGs and the STR are
both affected by aging (Figures 1, 2, 3). Interestingly, no further
Figure 3. Effect of aging on the photopic ERG and its daily rhythm. (A) The amplitude of b wave of the photopic ERG at ZT6 was not affected
by age at ZT6 (Two-way ANOVA, P.0.1). (B) It showed a significant decrease at ZT18 (Two-way ANOVA, P, 0.01, followed by Tukey tests, P,0.05) A
significant difference in the amplitude of the b wave between ZT6 and ZT18 was only detected in 3-month-old mice (Two-way ANOVA, P.0.1
followed by Tukey tests, P,0.05). Closed circles, open circles, and closed triangle indicate 3-, 6- and 12-month-old mice, respectively. Each data point
represents 4 to 8 animals, and the mean 6 SEM, where N=6–8 for each point. Figures C through E show representative wave forms of each age
group at ZT18 (C=3 months; D=6 months and E=12 months).
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org4 May 2012 | Volume 7 | Issue 5 | e37799
decrease in the amplitude of the a and b waves was observed after
12 months of age for both scotopic and photopic conditions. The
observation that the STR is only affected by aging at ZT18 is not
surprising, since mice are nocturnal and therefore the visual
system is optimized to perform at night when the mice are active.
Previous studies have shown that photoreceptor loss is only
observed in mice older than 12 months [4,13,14] with no
significant changes observed before this age [4,13]. Our
immunocitochemistry analysis (Figures 4) indicates that many of
the retinal biomarkers are not affected by aging in C3H-f+/+mice.
In our retina samples of 12 months age, the only effect seen in the
retina (i.e., the retraction of the photoreceptor and sprouting of the
bipolar cells dendrites) is congruent with the aging signature
already reported in literature [21,22]. This result suggests the
future search and quantification of markers, which might help
explain our ERG finding, will require a detailed analysis on other
components of the signaling pathways, such as the amount of
rhodopsin or of other phototransduction proteins, the distribution
of mGluR6, or the number of rod and on-cone bipolar cells. Our
data also indicate that the decrease in retinal functioning (ERG)
and sensitivity (STR) is important for the early detection of
photoreceptor dysfunctions, preceding any obvious morphological
change in retinal organization.
Several investigations have shown that blood melatonin levels or
biosynthesis decline with age . It has been also reported that a
similar scenario may be present in the retina since the level of
Arylalkylamine N-acetyltransferase, a key enzyme for melatonin
synthesis, transcription or protein expression, decreases with age
[25,26]. Our previous work showed that in melatonin-proficient
mice, the daily rhythms observed in ERG parameters are
controlled by melatonin ; therefore, we hypothesized that the
observed decline in the amplitudes of the ERG and the loss of the
daily rhythm may be due to the decline of melatonin synthesis in
older mice. To test this, we administered exogenous melatonin to
mice of different ages. Surprisingly, we observed a dose- and age-
dependent increase in the responsiveness of the ERG to
administration of exogenous melatonin (Figure 5), which was not
rescued by exogenous melatonin. Such a result may suggest that
the reduction in the melatonin receptors is responsible for the lack
of responsiveness to the administration of exogenous melatonin.
Interestingly, a previous study has reported a loss of responsiveness
to administration of exogenous melatonin in the suprachiasmatic
nucleus (SCN) of aged mice ; in addition, melatonin receptor
expression decreases during aging in human SCN and in patients
affected by Alzheimer’s  and Parkinson’s diseases . Such
results may suggest that the lack of responsiveness to the
administration of exogenous melatonin is probably due a
reduction in the levels of melatonin receptors present in the
photoreceptors. Further studies will be required to address this
Melatonin and its analogues are currently used by millions of
people around the world to prevent aging, to improve sleep
performance, to ameliorate jet-lag symptoms and to treat
depression . Our new study indicates that responsiveness to
exogenous melatonin is affected by aging; therefore, in some
Figure 4. Retinal organization in C3H-f+ +/+ + at 12 months of age. TOTO-3 staining of nuclear layers (red in A and blue in B) reveals an intact
retinal layering in C3H-f+/+control 12-month-old mice. (A) Rod bipolar cells labelled by protein kinase c (PKCa) antibodies (green) have normal
morphology and layering. (B) PKCa antibodies show again RB (red) with normally distributed bassoon puncta (green) decorating their dendritic tips in
the opl. (C) Rod bipolar cells (RB) (red) have dendritic tips associated to green puncta, representing kinesins II positive synaptic ribbons. Most puncta
are appropriately confined in the opl, but some of them are displaced in the onl (arrows). (D) PKCa labelling of Rod bipolar cells (red) and PSD-95
(green). Most presynaptic endings of photoreceptors (labelled by PSD-95) are confined to the OPL, but a few are clearly seen in the onl (arrow). (E)
Antibodies against Goa (green), specific for depolarizing bipolar cells, in combination with PKCa (red) allow visualization of rod bipolar cells (yellow-
orange) and depolarizing cone bipolars (green, CB). Dendrites of both categories of cells are clearly visible (arrows). (F) Calbindin (red) in combination
with neurofilament (green) antibodies show a normal pattern of staining of horizontal cell bodies (HC), their axonal endings (yellow profiles in the
opl) and calbindin positive amacrine cells (AC). Neurofilament antibodies also stains ganglion cells (GC, arrow). (G) One tyrosine hydroxylase (TH)
positive amacrine cell with the typical large size body (arrow) and main dendritic plexus in the outermost part of the ipl. (H) Antibodies against the
enzyme glutamine synthase show the fine morphology of Mu ¨ller glial cells (green). Anti-glial fibrillary acidic protein (GFAP) antibodies show
astrocytes regularly placed at the innermost retinal margin (red, arrow). Scale bars are 20 mm. Ph: Photoreceptors; onl: outer nuclear; opl: outer
plexiform; inl: inner nuclear; ipl: inner plexiform; gcl: ganglion cell layer.
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org5 May 2012 | Volume 7 | Issue 5 | e37799
instances, melatonin treatment may not be effective due to lack or
reduced sensitivity of its receptors.
Materials and Methods
C3H/f+/+mice used in this study were bred and maintained at
Morehouse School of Medicine in a 12-h light/12-h dark cycle,
with lights on from zeitgeber time (ZT) 0 to ZT 12 with food and
water ad libitum. All experiments conformed to the NIH Guide on
the Care and Use of Laboratory Animals, and were approved by
the Institutional Animal Care and Use Committees of Morehouse
School of Medicine.
Mice were anesthetized with ketamine (80 mg/kg) and xylazine
(16 mg/kg). The pupils were dilated with 1% atropine and 2.5%
phenylephrine (Sigma, St. Louis, MO, USA), and mice were
placed on a regulated heating pad set at 37uC with feedback from
the rectal temperature probe. The eye was lubricated with saline
solution, and a contact lens type electrode (LKC Technologies
model: N1530NNC) was topically applied on the cornea. A needle
reference was inserted in other side of cheek, and the ground
needle was inserted into the base of tail. All preparation of ERG
recordings was conducted under red dim light (,3 lux, 15 W
Kodak safe lamp filter 1A, Eastman Kodak, Rochester, NY, USA).
All electrodes were connected to a Universal DC Amplifier
(LKC Technologies model UBA-4200) and bands were filtered
from 0.3 to 500 Hz. Data were recorded and analyzed by EM for
Windows (ver. 8.2.1, LKC Technologies). Core body temperature
was maintained in 37uC by a feedback temperature control system
(FHC inc., Bowdoin, ME) during whole ERG recording. In the
dark-adapted ERG protocol, seven series of flash intensity between
from 0.03 to 6.28 cd*s/m2were presented to the mouse eye.
Flashes were generated by 530-nm green LEDs in a Ganzfeld
illuminator (LKC Technologies), and intervals of flashes increased
from 0.612 to 30 s as intensity of the flashes increased. Responses
of 3–10 flashes were averaged to generate a waveform for each
step of light intensity, and a-wave and b-wave of ERG
measurement were analyzed from the trace of wave forms.
To measure the photopic ERG mice were placed in a Ganzfeld
illuminator and cone-associated activity was isolated by saturating
rods with 63 cd*s/m2of white background light. The four series of
consecutive 10 white flashes (79.06 cd*s/m2) were introduced at
2.5 min, 5 min, 10 min, and 15 min during the background light
exposure. Background light was left on for 15 min while photopic
ERGs records were measured . The traces of the ERG were
averaged and stored on a computer for later analysis. The
amplitude of the b-wave was measured from the trough of the a-
wave to the peak of the b-wave or, if no a-wave was present, from
the baseline to the b-wave peak. The spectral composition and
irradiance of the light was monitored by a radio-spectrophotom-
eter (USB 2000, Ocean Optics, Dunedin, FL). The STR was
determined using the same protocol described in Baba et al., .
Details about the antibodies and immunocytochemistry proce-
dures used to study retinal organization are described in detail in
published work [4,31].
Administration of Exogenous Melatonin
Melatonin (Sigma, St Louis, MO) was dissolved in ethanol and
then diluted with sterilized PBS in volume of 10 mL/kg. The
solution was administered to mice by intraperitoneal (i.p.) injection
Figure 5. Effect of administration of exogenous melatonin on the scotopic ERG at different ages. Melatonin injection (1 mg/Kg)
increased the amplitude of the a (A, B) and b wave (D, E) of the scotopic ERG in 3- and 6-month-old mice (Two-way ANOVA P,0.01, followed by
Tukey tests, P,0.05) with respect to the values obtained in control mice. The same dose did not increase the amplitude of the a and b wave in
12 months old mice (Two-way ANOVA, P.0.01, C, F). Melatonin injection (0.1 mg/Kg) increased the amplitude of the a and b waves of the scotopic
ERG in 3-month-old mice (Two-way ANOVA, P,0.01, followed by Tukey tests, P,0.05 A, D), but not in 6 month-old mice (Two-way ANOVA, P.0.05;
B, E, C, F). White circles indicate control groups; black triangles indicate melatonin 0.01 mg/kg; white squares indicate melatonin 0.1 mg/kg; and black
circles indicate melatonin 1 mg/kg. Each value represents the mean 6 SEM, N=5–6 for each point.
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org6 May 2012 | Volume 7 | Issue 5 | e37799
at 1 mg/kg if not otherwise indicated. The same volume of vehicle Download full-text
alone was injected to the control group animals Melatonin or
vehicle was injected 1h before ERG recordings just before mice
were placed in the dark isolated chamber. All melatonin injections
were given at ZT 5 when endogenous melatonin level is
Comparison among the values obtained with the mice at
different ages and light intensity were performed using a Two-vay
Analysis of Variance (variable 1: age and variable 2: luminance)
when the analysis of variance indicated a significant effects of age
and light intensity (P,0.05) and a non significant interaction
between age and luminance (P.0.05) we performed a multiple
comparison test (Tukey tests, P,0.05). The STR was determined
using a t-test as described in . All the statistical tests were
performed using a statistical package (Sigma-Stat, 3.5).
Conceived and designed the experiments: GT ES KB. Performed the
experiments: KB SO AS FM SCA. Analyzed the data: KB ES FM GT.
Contributed reagents/materials/analysis tools: ES GT. Wrote the paper:
GT KS ES.
1.Tosini G, Davidson AJ, Fukuhara C, Kasamatsu M, Castanon-Cervantes O
(2007) Localization of a circadian clock in mammalian photoreceptors. FASEB
J. 21: 3866–3871.
Rufiange M, Dumont M, Lachappelle P (2002) Correlating retinal function with
melatonin secretion in subject with an early or late circadian phase. Invest
Ophthalmol Vis Sci. 43: 2491–2499.
Peters JL, Cassone VM (2005) Melatonin regulates circadian electroretinogram
rhythms in a dose- and time-dependent fashion. J Pineal Res. 38: 209–215.
Baba K, Pozdeyev N, Mazzoni F, Contreras-Alcantara S, Liu C, et al. (2009)
Melatonin modulates visual function and cell viability in the mouse retina via the
MT1 melatonin receptor. Proc Natl Acad Sci U S A 106: 15043–15048.
Gagne AM, Danilenko KV, Rosolen SG, Herbert M (2009) Impact of oral
melatonin on the electroretinogram. J Circadian Rhythms 7: 14.
Sugawara T, Sieving PA, luvone PM, Bush RA (1998) The melatonin antagonist
luzindole protects retinal photoreceptors from light damage in the rat. Invest
Ophthalmol Vis Sci. 39: 2458–2465.
Liang FQ, Aleman TS, Yang Z, Cideciyan AV, Jacobson SG, et al. (2001)
Melatonin delays photoreceptor degeneration in the rds/rds mouse. Neurore-
port 12: 1011–1014.
Yi C, Pan X, Yan H, Guo M, Pierpaoli W (2005) Effects of melatonin in age-
related macular degeneration. Ann N Y Acad Sci. 1057: 384–92.
Rosen R, Hu DN, Perez V, Tai K, Yu GP, et al. (2009) Urinary 6-
sulfatoxymelatonin level in age-related macular degeneration patients. Mol Vis.
10. Fujieda H, Hamadanizadeh SA, Wankiewicz E, Pang SF, Brown GM (1999)
Expression of mt1 melatonin receptor in rat retina: evidence for multiple cell
targets for melatonin. Neuroscience 93: 793–799.
11. Sengupta A, Baba K, Mazzoni F, Pozdeyev NV, Strettoi E, et al. (2011)
Localization of melatonin receptor 1 in mouse retina and its role in the circadian
regulation of the electroretinogram and dopamine levels. PLoS One. 6: e24483.
12. Meyer P, Pache M, Loeffler KU, Brydon L, Jockers R, et al. (2002) Melatonin
MT-1-receptor immunoreactivity in the human eye. Br J Ophthalmol 86:
13. Li C, Cheng M, Yang H, Peachey NS, Naash MI (2001) Age-related changes in
the mouse outer retina. Optom Vis Sci. 78: 425–430.
14. Gresh J, Goletz PW, Crouch RK, Rohrer B (2003) Structure-function analysis of
rods and cones in juvenile, adult, and aged C57bl/6 and Balb/c mice. Vis
Neurosci. 20: 211–20.
15. Goto M, Oshima I, Tomita T, Ebihara S (1989) Melatonin content of the pineal
gland in different mouse strains. J. Pineal Res. 7: 195–204.
16. Tosini G, Menaker M (1998) The clock in the mouse retina: melatonin synthesis
and photoreceptor degeneration. Brain Res. 789: 221–228.
17. Roseboom PH, Namboodiri MA, Zimonjic DB, Popescu NC, Rodriguez IR, et
al. (1998) Natural melatonin ‘knockdown’ in C57BL/6J mice: rare mechanism
truncates serotonin N-acetyltransferase. Brain Res Mol Brain Res. 63: 189–97.
18. Bubenik GA, Konturek SJ (2011) Melatonin and aging: prospects for human
treatment. J Physiol Pharmacol. 62: 13–19.
19. Jeon CJ, Strettoi E, Masland RH (1998) The major cell populations of the mouse
retina. J Neurosci. 18: 8936–8946.
20. Damiani D, Alexander JJ, O’Rourke JR, McManus M, Jadhav AP, et al. (2008)
Dicer inactivation leads to progressive functional and structural degeneration of
the mouse retina. J Neurosci. 28: 4878–4887.
21. Liets LC, Eliasieh K, van der List DA, Chalupa LM (2006) Dendrites of rod
bipolar cells sprout in normal aging retina. Proc Natl Acad Sci U S A. 103:
22. Terzibasi E, Calamusa M, Novelli E, Domenici L, Strettoi E, et al. (2009) Age-
dependent remodelling of retinal circuitry. Neurobiol Aging 30: 819–28.
23. Vivien-Roels B, Malan A, Rettori MC, Delagrange P, Jeanniot JP, et al. (1998)
Daily variations in pineal melatonin concentrations in inbred and outbred mice.
J Biol Rhythms. 13: 403–409.
24. Birch DG, Anderson JL (1992) Standardized full-field electroretinography.
Normal values and their variation with age. Arch Ophthalmol. 110: 1571–1576.
25. Pulido O, Clifford J (1986) Age-associated changes in the circadian rhythm of
retinal N-acetylserotonin and melatonin in rats with pigmented eyes. Exp
Gerontol. 21: 23–30.
26. Tosini G, Chaurasia SS, Iuvone PM (2006) Regulation of AANAT in the retina.
Chronobiology International 23: 381–391.
27. Von Gall C, Weaver DR (2008) Loss of responsiveness to melatonin in the aging
mouse suprachiasmatic nucleus. Neurobiol Aging. 29: 464–70.
28. Wu YH, Zhou JN, Van Heerikhuize J, Jockers R, Swaab DF (2007) Decreased
MT1 melatonin receptor expression in the suprachiasmatic nucleus in aging and
Alzheimer’s disease. Neurobiol Aging 28: 1239–1247.
29. Adi N, Mash DC, Ali Y, Singer C, Shehadeh L, et al. (2010) Melatonin MT1
and MT2 receptor expression in Parkinson’s disease. Med Sci Monit. 16: 61–67.
30. Sa ´nchez-Barcelo ´ EJ, Mediavilla MD, Tan DX, Reiter RJ (2010) Clinical uses of
melatonin: evaluation of human trials. Curr Med Chem. 17: 2070–2095.
31. Gargini C, Terzibasi E, Mazzoni F, Strettoi E (2007) Retinal organization in the
retinal degeneration 10 (rd10) mutant mouse: a morphological and ERG study.
J Comp Neurol 500: 222–238.
Age-Related Changes in the Mouse ERG
PLoS ONE | www.plosone.org7 May 2012 | Volume 7 | Issue 5 | e37799