- Email: [email protected]
Blue cone function in the retina of the cat
Vision RG. Vol. fb. pp. ‘99 to 801 Pergamon
Press 1976.
Printed m Great Bntain
BLUE CONE FUNCTION IN THE RETINA OF THE CAT’ ARXOLD R. Rxst~,
LEMHEM MEHMFEY, III
and ELIOTL. BERSON’
Berman-Cund Laboratory, Harvard Medical School, Massachusetts Eye C Ear Infirmary, 243 Charles Street, Boston, MA 02114, LISA.
(Rrceicrtl 20 July 1975: in recisetlf‘urm 13 &t&r
1975)
Abstract-Selective chromatic adaptation revealed the presence of a blue-sensitive mechanism in the cone electroretinogram of the cat. This mechanism &,,, near 460 nm), narrower than a Dartnall nomogram (460 nm), suggests the interaction of at least two cone photoreceptor systems in the pre-ganglion cell retina.
IS~OD~~~ON
Cats trained to discriminate colors under mesopic conditions retained this ability under bright photopic conditions sufficient to saturate the rod system (Daw and Pearlman, 1970). This suggested the presence of more than a single cone photoreceptor type. Microelectrode recordings from ganglion cells in the cat retina raised the possibility of more than one cone mechanism (Granit, 1945; Granit and TanSley, 1948). Pearlman and Daw (1970) detected color opponent ceils in the cat lateral genicuiate nucleus with inputs from retinal mechanics with spectrai sensitivity maxima near 450 and 556 mn. However, Dodt and Walther (1958). using flicker electroretmography, reported only one cone photoreceptor mechanism (&l,X near 560 nm). These findings prompted this study to determine whether or not more than one cone mechanism could be detected in the electroretinogram (ERG) of the cat.
the cornea were determined with a snectroradiometer. A correction was made for the spectrai absorbance of the cat lens (Weale, 1954). Eiectroretinographic testing was performed on four adult cats anesthetized with sodium pentobarbitai (40 mpikg) administered by the intraperitoneai route. Since retinal degenerations involving the cone photoreceptor system occur sporadically in cats, ail cats were examined to rule out the presence of a retinal degeneration involving the cone photoreceptor system (Rabin, Hayes and Berson, 1973). Pupils were maximally dilated with 10% phenylephrine hydrochloride and 1% cyciopentoiate hydrochloride. Signals were recorded at the cornea with a Buria~Aiien double electrode contact lens, amplified (x l~,~~, and then summed with a computer of average transients. The rod contribution to the ERG was eliminated by presenting a 4%Hz Bickering stimulus (Dodt and Enroth, 1953; Dodt and Walther, 1958). Spectral sensitivity data was derived from measurements at each wavelength of the log relative quantum flux required to elicit a criterion response.
MITERIALS rLvD METHODS
RESULTS
A two-channel Maxwellian view system was used for these studies. Light for the stimulus channel was provided by a 1 kW xenon arc lamp. Stimulus wavelength was seiected by placing Baird Atomic (10 i: 2 nm half peak band width) interference filters or Corning or Wratten. filters in the stimulus beam; stimulus intensity was controlled by adjusting balanced neutral density wedges. A sector disc (SO?; duty cycle) was used to present a flickering (40 Hz) stimulus. Light for the adapting field (background) was provided by a 50-W tungsten-halide lamp. The color of the background was determined by interposing either broad-band Corning filters or a Cinnemoid filter. The stimuhts subtended a visual angJe of 45” and was centrally superimposed on a 6O- background. Quantum fluxes at
Figure 1 shows that short (Wratten 98) and long (Coming 2418) waveI~~h stimuli (40 Hz) matched +fo background Long
WClYe
‘d-%--L/
short wave
h //.a
Dtfference
I
stimu+ur,
-L-X
YIflow
background
-
-
^J/L/-LrL --XL
Fig. 1. ERG responses to long wavelength (Coming 2418, Row 1) and short wavelength (Wratten 98, Row 2) stimuli matched in brightness to elicit equal amplitude responses at 30Hz in the absence of any background adaptation (left) elicit mismatched responses in the presence of a bright yellow background (right). Row 3 (Difference) illustrates respectively results of subtraction of the long wavelength from the short wavelength responses elicited without (left) and with (right) chromatic adaptation. Calibration symbols (Row 4) were recorded from a photocell facing the stimulus beam (40 HZ) and represent 2 ,uV vertically for the left column and 0.5 pV vertically for the right column.
’ This work was supported in part by Public Health Service Grant EY-00169 and Research Career Develop ment Award EY-70800 from the National Eye Institute (Dr. Berson), NE1 Postdoctoral Fellowship lF02EY54841-01 (Dr. Mehaffey), and in part by the National Retinitis Pigmentosa Foundation, Baltimore, Maryland and the George Gund Foundation, Cleveland. Ohio. ’ Reprint requests to Dr. Eliot L. Berson, Berman-Gund Laboratory. 243 Charles Street, Boston, MA 02114. U.S.A. 799
I 400
I
I
500 Wavelength,
600
I 7cKl
nm
Fig. 2. Spectral sensitivity of the cat eye to 40 Hz stimuli in the absence of any background adaptation (open circles, top) and to 40 Hz stimuh in the presence of a bright (7 log td) yellow (Coming 3384, i. > 470 nmf adapting light
[solid circles, bottom).
in brightness to elicit respectively equal amplitude rewith no background (left column), elicited unequal responses (right column) in the presence of a bright (7 log td) yellow background (Coming 3384, sharp cut filter with less than I”/6transmission of light at wavelengths below 470 nm). Amplitudes of the responses to the matched short (Wratten 98) and long (Corning 2418) wavelength stimuli (40 Hz) remained equal in the presence of other backgrounds with less than 1’~ tr~smi~ion beIow 510 nm (for example, Coming 34863. Figure 2 (open circles) shows spectral sensitivity measurements derived from ERG responses to a 40-Hz stimulus. Peak retinal sensitivity is near 560 nm. Fieure 2 (solid circles) shows the ERG spectral sensitiv%y of the cat retina measured at 40 Hz in the presence of the bright yellow (Corning 3384) background. Peak retinal sensitivity is near 460 nm. An attempt was made to detect a cone mechanism with peak sensitivity above 560 nm. Chromatic adaptation with a blue-green Cinnemoid 16 (j. < 560 nm) background (5 log td) was not effective in altering equal responses to narrow band (540 and 600 nm) stimuli matched at 40 Hz {without any background). sponses
mechanisms (160 and %O nm, approximacz those obtained (430 and 556 nmj vtith micro&ctro& recordings from the cat lateral geniculate nucleus (PearLman and Daw, 1970). The small size of the blue cone ERG response ( < 2 ,uvJ suggests that the number of blue cone photoreceptors is sma& although the effect of reflected light (;. > 510 nm) from the tapetum (Weale. 1953) would serve to enhance the amplitude of the long wavelength mechanism (&nX= 560 nm) relative to that of a cone photopi_ment mechanism with peak sensitivity in the short wavelength portion of the spectrum. The idea that the number of blue cone photoreceptors is small is also supported by the finding of only 3 color opponent cells with peak sensitivities near 450 nm compared with 115 cells with peak sensitivities near 556 nm in the cat lateral geniculate nucleus (Pearlman and Daw, 1970). The long wavelength mechanism obtained in this study is virtually identical to that obtained with ERG recording by Dodt and Walther (1958) and closely approximates a Dartnall nomogram (560 nm). The blue cone mechanism separated in the ERG of the cynomolgus monkey with chromatic adaptation (E.mZx near 460 nm) also has an ERG action spectrum that closely approximates a Dartnall nomo~am (450 nm); this mechanism sums linearly with the green and red cone mechanisms to generate the dark-adapted cone ERG in the monkey (Mehaffey and Berson, 1974). In contrast, in the cat, the short wavelength mechanism (&,,, near 460 nm), revealed by linear subtraction of data of the dark-adapted ERG (Fig. 2, open circles) from data of the yellow-adapted ERG (Fig. 2, solid circles), is considerably narrower (Fig. 3. solid circles) than the absorption spectrum that would be predicted from a Dartnall nomogram (460
I
.o f
0.2
~
OL L
I
Wavelength,
DISCUSSION The fmding of responses matched in amplitude at 40 Hz (with no background) and mismatched responses to these same stimuli presented respectively in the presence of a bright yeliow background demonstrates the presence of at least two cone mechanisms in the cat ERG. The peak sensitivities of these
I 600
500
400
nm
Fig. 3. Solid circles represent spectral sensitivity of a short wavelength mechanism derived from linear subtraction of the ERG spectral sensitivity (40 Hz) with a background (Fig. 2) from the ERG spectral sensitivity (40 Hz) obtained in the rxesence of a bri.ght yellow background (Fig. 2). Data (open and solid circles) shown in Fig 2 were plotted on linear coordinates prior to this subtraction. Squares represent spectral sensitivity of Granit’s (1945) blue cone modulator obtained with microelectrode recordings from the ganglion cells of the cat retina.
Blue cone function in the retina of thr cat
~III)~. An interaction between more than one cone photoreceptor type in the pre-ganglion cell retina of the cat could explain this fmdmg in the ERG. Granit’s (1945) blue cone modulator (1.,,, near 460 nm). also narrower (Fig. 3, squares) than a Dartnall nomogram (460 nm), suggests that the results of such interaction are detectable at the ganglion cell level. 3 A comparison of our results with those obtained with microspectrophotometric measurements of the blue cones of the goldfish (Liebman and Entine, 1964) demonstrates that our curve and theirs have nearly the same peak wavelength (460 vs 4% nmf. but their curve is broader than a Dartnafl nomogram (4% nm) while ours is considerably narrower. Weale‘s (19%) data obtained by the method of reflection densitometry in the cat Tfelds a difference spectrum which also has a peak sensltlvity near 460 nm and which is also much narrower than a Dartnall nomogram (460 nm). However. such difference spectrum data is difiicult to interpret because of the presence of photoproducts of bleaching that absorb in the short wavelength portion of the spectrum.
REFERENCES Daw N. W. and Rarlman A. L. (1970) Cat color vision: evidence for more than one cone process. J. F~~sjo~. Lo&. 211. 1X-136.
801
Dodt E. and Enroth C. (19%) Retinal Hicker response in the cat. rleru phyrioI. scnnci. 30. 37%390. Dodt E. and Walcher J. B. (1933) Der photopische dominatar in Himmer-ERG der katze. fjiigrrs .-lrclz. grs. Phpsiol. 266. 17%IY6. Granit R. (1945) The colour receptors of the mammalian retina. J. l\irurophysiol. 8. 195-217. Granit R. and Tanslev K. (1945) Rods. cones and the localization of pre-excitator inhibition in the mammalian retina. J. Ph.vsiol., Land. 154. S-66. Liebman P. A. and Entine G. (1964) Sensitive low-linhtlevel microspectrophotometer’ detection of ph&os&itive pigments of retinal cones. J. opt. Sot. Am. 54, 1151-1459.
Mehaffey L. and Berson E. L. (1974) Cone mechanisms in the electroretinogram of the cynomolgus monkey. Incesrre Ophrh. 13. 266-273. Pearlman A. L. and Daw N. W. (1970) Opponent color cells in the cat lateral geniculate nucleus. Science 167, 84-86. Rabin A. R.. Hayes K. C. and Berson E. L. (1973) Cone and rod responses in nutritionally induced retinal degeneration in the cat. Inrestre Ophrh. 11, 694-704. Weale R. A. (1953) The spectral sensitivity of the cat’s tapeturn measured in situ. j. Phpiol., to&. 119, 3@-42. Weale R. A. (1954) Light absorption in the crystalline lens of the cat. Nature, ton&. 173, 104Q-1050. Weale R. A. (1935) In Receptors and Sensory Perception (Edited by Granit R.), p. 136. Yale Univ. Press, New Haven.
Press 1976.
Printed m Great Bntain
BLUE CONE FUNCTION IN THE RETINA OF THE CAT’ ARXOLD R. Rxst~,
LEMHEM MEHMFEY, III
and ELIOTL. BERSON’
Berman-Cund Laboratory, Harvard Medical School, Massachusetts Eye C Ear Infirmary, 243 Charles Street, Boston, MA 02114, LISA.
(Rrceicrtl 20 July 1975: in recisetlf‘urm 13 &t&r
1975)
Abstract-Selective chromatic adaptation revealed the presence of a blue-sensitive mechanism in the cone electroretinogram of the cat. This mechanism &,,, near 460 nm), narrower than a Dartnall nomogram (460 nm), suggests the interaction of at least two cone photoreceptor systems in the pre-ganglion cell retina.
IS~OD~~~ON
Cats trained to discriminate colors under mesopic conditions retained this ability under bright photopic conditions sufficient to saturate the rod system (Daw and Pearlman, 1970). This suggested the presence of more than a single cone photoreceptor type. Microelectrode recordings from ganglion cells in the cat retina raised the possibility of more than one cone mechanism (Granit, 1945; Granit and TanSley, 1948). Pearlman and Daw (1970) detected color opponent ceils in the cat lateral genicuiate nucleus with inputs from retinal mechanics with spectrai sensitivity maxima near 450 and 556 mn. However, Dodt and Walther (1958). using flicker electroretmography, reported only one cone photoreceptor mechanism (&l,X near 560 nm). These findings prompted this study to determine whether or not more than one cone mechanism could be detected in the electroretinogram (ERG) of the cat.
the cornea were determined with a snectroradiometer. A correction was made for the spectrai absorbance of the cat lens (Weale, 1954). Eiectroretinographic testing was performed on four adult cats anesthetized with sodium pentobarbitai (40 mpikg) administered by the intraperitoneai route. Since retinal degenerations involving the cone photoreceptor system occur sporadically in cats, ail cats were examined to rule out the presence of a retinal degeneration involving the cone photoreceptor system (Rabin, Hayes and Berson, 1973). Pupils were maximally dilated with 10% phenylephrine hydrochloride and 1% cyciopentoiate hydrochloride. Signals were recorded at the cornea with a Buria~Aiien double electrode contact lens, amplified (x l~,~~, and then summed with a computer of average transients. The rod contribution to the ERG was eliminated by presenting a 4%Hz Bickering stimulus (Dodt and Enroth, 1953; Dodt and Walther, 1958). Spectral sensitivity data was derived from measurements at each wavelength of the log relative quantum flux required to elicit a criterion response.
MITERIALS rLvD METHODS
RESULTS
A two-channel Maxwellian view system was used for these studies. Light for the stimulus channel was provided by a 1 kW xenon arc lamp. Stimulus wavelength was seiected by placing Baird Atomic (10 i: 2 nm half peak band width) interference filters or Corning or Wratten. filters in the stimulus beam; stimulus intensity was controlled by adjusting balanced neutral density wedges. A sector disc (SO?; duty cycle) was used to present a flickering (40 Hz) stimulus. Light for the adapting field (background) was provided by a 50-W tungsten-halide lamp. The color of the background was determined by interposing either broad-band Corning filters or a Cinnemoid filter. The stimuhts subtended a visual angJe of 45” and was centrally superimposed on a 6O- background. Quantum fluxes at
Figure 1 shows that short (Wratten 98) and long (Coming 2418) waveI~~h stimuli (40 Hz) matched +fo background Long
WClYe
‘d-%--L/
short wave
h //.a
Dtfference
I
stimu+ur,
-L-X
YIflow
background
-
-
^J/L/-LrL --XL
Fig. 1. ERG responses to long wavelength (Coming 2418, Row 1) and short wavelength (Wratten 98, Row 2) stimuli matched in brightness to elicit equal amplitude responses at 30Hz in the absence of any background adaptation (left) elicit mismatched responses in the presence of a bright yellow background (right). Row 3 (Difference) illustrates respectively results of subtraction of the long wavelength from the short wavelength responses elicited without (left) and with (right) chromatic adaptation. Calibration symbols (Row 4) were recorded from a photocell facing the stimulus beam (40 HZ) and represent 2 ,uV vertically for the left column and 0.5 pV vertically for the right column.
’ This work was supported in part by Public Health Service Grant EY-00169 and Research Career Develop ment Award EY-70800 from the National Eye Institute (Dr. Berson), NE1 Postdoctoral Fellowship lF02EY54841-01 (Dr. Mehaffey), and in part by the National Retinitis Pigmentosa Foundation, Baltimore, Maryland and the George Gund Foundation, Cleveland. Ohio. ’ Reprint requests to Dr. Eliot L. Berson, Berman-Gund Laboratory. 243 Charles Street, Boston, MA 02114. U.S.A. 799
I 400
I
I
500 Wavelength,
600
I 7cKl
nm
Fig. 2. Spectral sensitivity of the cat eye to 40 Hz stimuli in the absence of any background adaptation (open circles, top) and to 40 Hz stimuh in the presence of a bright (7 log td) yellow (Coming 3384, i. > 470 nmf adapting light
[solid circles, bottom).
in brightness to elicit respectively equal amplitude rewith no background (left column), elicited unequal responses (right column) in the presence of a bright (7 log td) yellow background (Coming 3384, sharp cut filter with less than I”/6transmission of light at wavelengths below 470 nm). Amplitudes of the responses to the matched short (Wratten 98) and long (Corning 2418) wavelength stimuli (40 Hz) remained equal in the presence of other backgrounds with less than 1’~ tr~smi~ion beIow 510 nm (for example, Coming 34863. Figure 2 (open circles) shows spectral sensitivity measurements derived from ERG responses to a 40-Hz stimulus. Peak retinal sensitivity is near 560 nm. Fieure 2 (solid circles) shows the ERG spectral sensitiv%y of the cat retina measured at 40 Hz in the presence of the bright yellow (Corning 3384) background. Peak retinal sensitivity is near 460 nm. An attempt was made to detect a cone mechanism with peak sensitivity above 560 nm. Chromatic adaptation with a blue-green Cinnemoid 16 (j. < 560 nm) background (5 log td) was not effective in altering equal responses to narrow band (540 and 600 nm) stimuli matched at 40 Hz {without any background). sponses
mechanisms (160 and %O nm, approximacz those obtained (430 and 556 nmj vtith micro&ctro& recordings from the cat lateral geniculate nucleus (PearLman and Daw, 1970). The small size of the blue cone ERG response ( < 2 ,uvJ suggests that the number of blue cone photoreceptors is sma& although the effect of reflected light (;. > 510 nm) from the tapetum (Weale. 1953) would serve to enhance the amplitude of the long wavelength mechanism (&nX= 560 nm) relative to that of a cone photopi_ment mechanism with peak sensitivity in the short wavelength portion of the spectrum. The idea that the number of blue cone photoreceptors is small is also supported by the finding of only 3 color opponent cells with peak sensitivities near 450 nm compared with 115 cells with peak sensitivities near 556 nm in the cat lateral geniculate nucleus (Pearlman and Daw, 1970). The long wavelength mechanism obtained in this study is virtually identical to that obtained with ERG recording by Dodt and Walther (1958) and closely approximates a Dartnall nomogram (560 nm). The blue cone mechanism separated in the ERG of the cynomolgus monkey with chromatic adaptation (E.mZx near 460 nm) also has an ERG action spectrum that closely approximates a Dartnall nomo~am (450 nm); this mechanism sums linearly with the green and red cone mechanisms to generate the dark-adapted cone ERG in the monkey (Mehaffey and Berson, 1974). In contrast, in the cat, the short wavelength mechanism (&,,, near 460 nm), revealed by linear subtraction of data of the dark-adapted ERG (Fig. 2, open circles) from data of the yellow-adapted ERG (Fig. 2, solid circles), is considerably narrower (Fig. 3. solid circles) than the absorption spectrum that would be predicted from a Dartnall nomogram (460
I
.o f
0.2
~
OL L
I
Wavelength,
DISCUSSION The fmding of responses matched in amplitude at 40 Hz (with no background) and mismatched responses to these same stimuli presented respectively in the presence of a bright yeliow background demonstrates the presence of at least two cone mechanisms in the cat ERG. The peak sensitivities of these
I 600
500
400
nm
Fig. 3. Solid circles represent spectral sensitivity of a short wavelength mechanism derived from linear subtraction of the ERG spectral sensitivity (40 Hz) with a background (Fig. 2) from the ERG spectral sensitivity (40 Hz) obtained in the rxesence of a bri.ght yellow background (Fig. 2). Data (open and solid circles) shown in Fig 2 were plotted on linear coordinates prior to this subtraction. Squares represent spectral sensitivity of Granit’s (1945) blue cone modulator obtained with microelectrode recordings from the ganglion cells of the cat retina.
Blue cone function in the retina of thr cat
~III)~. An interaction between more than one cone photoreceptor type in the pre-ganglion cell retina of the cat could explain this fmdmg in the ERG. Granit’s (1945) blue cone modulator (1.,,, near 460 nm). also narrower (Fig. 3, squares) than a Dartnall nomogram (460 nm), suggests that the results of such interaction are detectable at the ganglion cell level. 3 A comparison of our results with those obtained with microspectrophotometric measurements of the blue cones of the goldfish (Liebman and Entine, 1964) demonstrates that our curve and theirs have nearly the same peak wavelength (460 vs 4% nmf. but their curve is broader than a Dartnafl nomogram (4% nm) while ours is considerably narrower. Weale‘s (19%) data obtained by the method of reflection densitometry in the cat Tfelds a difference spectrum which also has a peak sensltlvity near 460 nm and which is also much narrower than a Dartnall nomogram (460 nm). However. such difference spectrum data is difiicult to interpret because of the presence of photoproducts of bleaching that absorb in the short wavelength portion of the spectrum.
REFERENCES Daw N. W. and Rarlman A. L. (1970) Cat color vision: evidence for more than one cone process. J. F~~sjo~. Lo&. 211. 1X-136.
801
Dodt E. and Enroth C. (19%) Retinal Hicker response in the cat. rleru phyrioI. scnnci. 30. 37%390. Dodt E. and Walcher J. B. (1933) Der photopische dominatar in Himmer-ERG der katze. fjiigrrs .-lrclz. grs. Phpsiol. 266. 17%IY6. Granit R. (1945) The colour receptors of the mammalian retina. J. l\irurophysiol. 8. 195-217. Granit R. and Tanslev K. (1945) Rods. cones and the localization of pre-excitator inhibition in the mammalian retina. J. Ph.vsiol., Land. 154. S-66. Liebman P. A. and Entine G. (1964) Sensitive low-linhtlevel microspectrophotometer’ detection of ph&os&itive pigments of retinal cones. J. opt. Sot. Am. 54, 1151-1459.
Mehaffey L. and Berson E. L. (1974) Cone mechanisms in the electroretinogram of the cynomolgus monkey. Incesrre Ophrh. 13. 266-273. Pearlman A. L. and Daw N. W. (1970) Opponent color cells in the cat lateral geniculate nucleus. Science 167, 84-86. Rabin A. R.. Hayes K. C. and Berson E. L. (1973) Cone and rod responses in nutritionally induced retinal degeneration in the cat. Inrestre Ophrh. 11, 694-704. Weale R. A. (1953) The spectral sensitivity of the cat’s tapeturn measured in situ. j. Phpiol., to&. 119, 3@-42. Weale R. A. (1954) Light absorption in the crystalline lens of the cat. Nature, ton&. 173, 104Q-1050. Weale R. A. (1935) In Receptors and Sensory Perception (Edited by Granit R.), p. 136. Yale Univ. Press, New Haven.