Neuroscience 2002 Abstract
| Presentation Number: | 556.18 |
|---|---|
| Abstract Title: | The Relationship Between Ambient Lighting Conditions, Absolute Dark-Adapted Thresholds, and Rhodopsin In Black and Albino Mice. |
| Authors: |
Balkema, G. W.*1
; Hamdy, G. H.1
; DiLeonardo, J. M.1
; Balkema, N. R.1
1Biology Department, Boston Col, Chestnut Hill, MA |
| Primary Theme and Topics |
Sensory Systems - Vision -- Retina and photoreceptors |
| Session: |
556. Vision: retina III Poster |
| Presentation Time: | Tuesday, November 5, 2002 2:00 PM-3:00 PM |
| Location: | Hall A2-B3 E-122 |
| Keywords: | PHOTORECEPTOR, VISUAL, SENSORY, REGULATION |
We have observed significant variation in absolute dark-adapted thresholds both within and between strains of mice with differing pigmentation levels. Differences in sensitivity within a single strain appear to be related to the Williams' photostasis effect (Balkema, DiLeonardo & Hamdy, SFN, San Deigo, 2001), i.e., photoreceptor rhodopsin levels are dependent upon ambient lighting conditions. In the present study, we maintained albino mice (c2J/c2J) at 10 -4 cd/m2 (dim) and black mice at 103 cd/m2 (bright) in order to equalize their rhodopsin levels. This resulted in ocular rhodopsin levels for albino mice (albino-dim) that were 494 ± 11 pmoles/eye and rhodopsin levels for black mice (black-bright) that were 506 ± 25 pmoles/eye. For comparison, rhodopsin levels in black mice maintained under dim light were 586 ± 46 pmoles/eye and 217 ± 46 pmoles/eye in albino mice maintained in bright light.
Absolute dark-adapted thresholds determined with a water maze test showed that albino and black mice with equivalent rhodopsin levels had similar dark-adapted thresholds: 6.38 log cd/m2 vs. 6.47 log cd/m2 (respectively). This suggests that dark-adapted thresholds are directly related to rhodopsin levels regardless of the level ocular melanin pigmentation. Measurements of photoreceptor outer segment length and the number of photoreceptors in albino and black mice maintained under these lighting conditions are currently underway to rule out alternative explanations. We hypothesize that the absolute dark-adapted threshold deficit that is observed in hypopigmented mutants is a result of abnormalities in rhodopsin level regulation.
Absolute dark-adapted thresholds determined with a water maze test showed that albino and black mice with equivalent rhodopsin levels had similar dark-adapted thresholds: 6.38 log cd/m2 vs. 6.47 log cd/m2 (respectively). This suggests that dark-adapted thresholds are directly related to rhodopsin levels regardless of the level ocular melanin pigmentation. Measurements of photoreceptor outer segment length and the number of photoreceptors in albino and black mice maintained under these lighting conditions are currently underway to rule out alternative explanations. We hypothesize that the absolute dark-adapted threshold deficit that is observed in hypopigmented mutants is a result of abnormalities in rhodopsin level regulation.
Supported by NSF IBN-9983297
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2002 Neuroscience Meeting Planner. Orlando, FL: Society for Neuroscience, 2002. Online.
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