Abstract:Key points• The mouse retina has become a key model for research on the function and dysfunction of the early stages of vision, but its photoreceptors have proven difficult to access with whole-cell recording techniques.• We have optimized the mouse retinal slice preparation to the degree required for studying photoreceptors with a reasonably high yield.• We find that single photon processing in rods is considerably more efficient than previously thought, implying a more favourable transmission at the rod-rod … Show more
“…This is strong evidence for the presence of rod input in cones.10.7554/eLife.01386.004Figure 2.Cones express a rod-like sensitivity to dim flashes and slow recovery after bright flashes.( A1 ) Response of a patched rod to the kinetics protocol (Figure 1C) in the first minutes after establishing the seal (black traces). At later times, a previously described rundown of kinetics was observed (gray traces; see Cangiano et al, 2012). ( A2 ) Loose seal recording showing a scaled version of the rod photovoltage in response to the kinetics protocol.…”
Section: Resultsmentioning
confidence: 57%
“…At later times, a previously described rundown of kinetics was observed (gray traces; see Cangiano et al, 2012). ( A2 ) Loose seal recording showing a scaled version of the rod photovoltage in response to the kinetics protocol.…”
Rod and cone photoreceptors are coupled by gap junctions (GJs), relatively large channels able to mediate both electrical and molecular communication. Despite their critical location in our visual system and evidence that they are dynamically gated for dark/light adaptation, the full impact that rod–cone GJs can have on cone function is not known. We recorded the photovoltage of mouse cones and found that the initial level of rod input increased spontaneously after obtaining intracellular access. This process allowed us to explore the underlying coupling capacity to rods, revealing that fully coupled cones acquire a striking rod-like phenotype. Calcium, a candidate mediator of the coupling process, does not appear to be involved on the cone side of the junctional channels. Our findings show that the anatomical substrate is adequate for rod–cone coupling to play an important role in vision and, possibly, in biochemical signaling among photoreceptors.DOI:
http://dx.doi.org/10.7554/eLife.01386.001
“…This is strong evidence for the presence of rod input in cones.10.7554/eLife.01386.004Figure 2.Cones express a rod-like sensitivity to dim flashes and slow recovery after bright flashes.( A1 ) Response of a patched rod to the kinetics protocol (Figure 1C) in the first minutes after establishing the seal (black traces). At later times, a previously described rundown of kinetics was observed (gray traces; see Cangiano et al, 2012). ( A2 ) Loose seal recording showing a scaled version of the rod photovoltage in response to the kinetics protocol.…”
Section: Resultsmentioning
confidence: 57%
“…At later times, a previously described rundown of kinetics was observed (gray traces; see Cangiano et al, 2012). ( A2 ) Loose seal recording showing a scaled version of the rod photovoltage in response to the kinetics protocol.…”
Rod and cone photoreceptors are coupled by gap junctions (GJs), relatively large channels able to mediate both electrical and molecular communication. Despite their critical location in our visual system and evidence that they are dynamically gated for dark/light adaptation, the full impact that rod–cone GJs can have on cone function is not known. We recorded the photovoltage of mouse cones and found that the initial level of rod input increased spontaneously after obtaining intracellular access. This process allowed us to explore the underlying coupling capacity to rods, revealing that fully coupled cones acquire a striking rod-like phenotype. Calcium, a candidate mediator of the coupling process, does not appear to be involved on the cone side of the junctional channels. Our findings show that the anatomical substrate is adequate for rod–cone coupling to play an important role in vision and, possibly, in biochemical signaling among photoreceptors.DOI:
http://dx.doi.org/10.7554/eLife.01386.001
“…Physiological and structural analysis in wild-type (wt) retinas previously demonstrated that cone photoreceptors are functionally coupled to rods [14], [15], [19]–[22]. This coupling is mediated by the gap junction protein connexin36 (Cx36) expressed on the cone side [11], [12], [14] and another, yet unknown connexin on the rod side.…”
Section: Resultsmentioning
confidence: 99%
“…Electrical coupling between rod and cone photoreceptors is the basic premise of the bystander hypothesis and has been demonstrated in a variety of animal models [44], including the mouse [14], [15], [19], [22], [45]. Although for the mouse only the connexin on the cone side is known (Cx36) [12], [13], several studies show that disruption of Cx36 is sufficient to disrupt rod-cone coupling [14]–[16].…”
Retinitis pigmentosa (RP) relates to a group of hereditary neurodegenerative diseases of the retina. On the cellular level, RP results in the primary death of rod photoreceptors, caused by rod-specific mutations, followed by a secondary degeneration of genetically normal cones. Different mechanisms may influence the spread of cell death from one photoreceptor type to the other. As one of these mechanisms a gap junction-mediated bystander effect was proposed, i.e., toxic molecules generated in dying rods and propagating through gap junctions induce the death of healthy cone photoreceptors. We investigated whether disruption of rod-cone coupling can prevent secondary cone death and reduce the spread of degeneration. We tested this hypothesis in two different mouse models for retinal degeneration (rhodopsin knockout and rd1) by crossbreeding them with connexin36-deficient mice as connexin36 represents the gap junction protein on the cone side and lack thereof most likely disrupts rod-cone coupling. Using immunohistochemistry, we compared the progress of cone degeneration between connexin36-deficient mouse mutants and their connexin36-expressing littermates at different ages and assessed the accompanied morphological changes during the onset (rhodopsin knockout) and later stages of secondary cone death (rd1 mutants). Connexin36-deficient mouse mutants showed the same time course of cone degeneration and the same morphological changes in second order neurons as their connexin36-expressing littermates. Thus, our results indicate that disruption of connexin36-mediated rod-cone coupling does not stop, delay or spatially restrict secondary cone degeneration and suggest that the gap junction-mediated bystander effect does not contribute to the progression of RP.
“…Due to their small size and complex biochemical machinery, mouse photoreceptors (and thus, in all likelihood, mammalian photoreceptors in general) are easily perturbed by the very same electrophysiological technique that is used to record from them: our lab has recently voiced this issue, showing that perforated patch recordings of mouse rods and cones can affect membrane potentials and flash response kinetics (Cangiano et al . ), as well as rod–cone coupling (Asteriti et al . ).…”
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