Mouse cone photoresponses obtained with electroretinogram from the isolated retina

Abstract

We characterize the dark-adapted photoresponses from mouse cones intact in the isolated retina, their virtually natural environment, by isolating pharmacologically the photoreceptor light responses from the electroretinogram (ERG). Due to the different photoresponse kinetics and sensitivity of rods and cones, the cone responses were readily attained by using a rod-saturating preflash. The stimulus wavelength (544 nm) was chosen to selectively stimulate the green sensitive ("M"-)pigment. Obtained responses were monophasic, showing fast kinetics (mean t(p)=51 ms) and low sensitivity (fractional single-photon response ca. 0.23%). The amplification coefficient of cones (4.6 s(-2)) was very close to that of rods (5.6 s(-2)), while the dominant time constant of recovery was clearly smaller for cones (33 ms) than for rods (160 ms).

Autophagy supports color vision

“…Perfusion solution was continuously bubbled with carbogen (5% CO 2 ) and maintained at 38 C. Photoreceptors were stimulated with 505-nm light that formed a homogenous spot overfilling the effective Ø0.5 mm recording area of the central retina. Cone responses were isolated by double flash technique 58 by using 88,000 photons (505 nm) mm ¡2 pre-flash (1 ms) followed by varying test flashes ranging from 700 to 14,000 photons mm ¡2 delivered 250 ms after the pre-flash when rods remained still saturated. The ERG signal was amplified by differential amplifier (DP-311, Warner Instruments), sampled at 10 kHz, low-pass filtered at 300 Hz (8-pole Bessel filter) and collected using a digitizer (Digidata 1440A,) and pCLAMP 9 software from Molecular Devices.…”

Mesopic background lights enhance dark-adapted cone ERG flash responses in the intact mouse retina: a possible role for gap junctional decoupling

“…Instead, we isolated the cone flash responses with a rod-saturating preflash producing 150,000 -260,000 Rh*. The preflash-test stimulus interval (typically 500 ms) was chosen to allow cone responses to recover from the preflash while the rods remained unresponsive (Heikkinen et al 2008, see also Figs. 2 and 3).…”

“…The method for obtaining isolated cone flash responses was adapted with minor modifications from Heikkinen et al (2008). The animals were dark-adapted overnight and killed with CO 2 asphyxiation and cervical dislocation.…”

“…The 532-and 543.5-nm lasers stimulate exclusively rods and the M-cone pigments in the mouse retina, as the UV-pigment absorbance is weakened by 7-8 log-units at these long wavelengths. To convert flash and background intensities (I F and I Bg , respectively, with subscript denoting the used wavelength) to activated rhodopsins per rod (Rh*, ⌽ rod and ⌽ Bg, rod ) or M-cone opsins per cone (P*, ⌽ cone and ⌽ Bg, cone ), the effective collection areas for rods and the M-pigment-driven responses of the cones at the central retina were calculated for our geometry as in Heikkinen et al (2008), and scaled to the stimulus wavelengths with the templates of Govardovskii et al (2000).…”

“…The 532-and 543.5-nm lasers stimulate exclusively rods and the M-cone pigments in the mouse retina, as the UV-pigment absorbance is weakened by 7-8 log-units at these long wavelengths. To convert flash and background intensities (I F and I Bg , respectively, with subscript denoting the used wavelength) to activated rhodopsins per rod (Rh*, ⌽ rod and ⌽ Bg, rod ) or M-cone opsins per cone (P*, ⌽ cone and ⌽ Bg, cone ), the effective collection areas for rods and the M-pigment-driven responses of the cones at the central retina were calculated for our geometry as in Heikkinen et al (2008), and scaled to the stimulus wavelengths with the templates of Govardovskii et al (2000).In brief, the rod outer segments were considered cylinders with diameter 1.4 m, length 24 m (Carter-Dawson and LaVail 1979), and specific absorbance 0.016 m Ϫ1 (Nymark et al 2005) at max (498 nm, Lyubarsky et al 1999). This led to an effective collection area a c, rod of 0.73 m 2 for axially incident light at max , with absorption scaled down by 0.69 and 0.5 at the stimulating and background wavelengths 532 and 543.5 nm, respectively.…”