Abstract
We measured the pupillary light reflex (PLR) in 5 pigmented, Long Evans rats (under urethan sedation) in three conditions: direct stimulation, consensual stimulation, and a control condition designed to measure the effects of stray light. The average constriction (maximal amplitude) produced by a ganzfeld stimulus delivering 1.6 log quanta absorbed per rod per sec for a duration of 3 sec was measured to be 0.78 ± 0.07mm for the direct PLR, 0.67 ± 0.06mm for the consensual PLR, and 0.07 ± 0.029mm for the control condition. We corrected the consensual measurement for each rat by subtracting the value of the control (stray-light induced) constriction. A comparison of the corrected consensual constriction to the direct constriction showed that, on average, the consensual constriction attained an amplitude of 78% of the direct constriction. Our findings contradict claims that the consensual pupillary light reflex is absent in rodents. Although our results are in agreement with findings showing bilateral projections of the retina to the pretectum (which subserves the pupillary light reflex) in the rat, the consensual-to-direct ratio we report is higher than might be expected from anatomical estimates of the overall proportion of uncrossed to crossed optic fibers in the rat.
Highlights
We measured the pupilla~ light reflex (PLR) in 5 pimento, Long Evans rats in three conditions: direct stimulation, consensual stimulation, and a controi condition designed to measure the effects of stray light
Our results are in agreement with findings showing bilaterat projections of the retina to the pre~t~rn in the rat, the con~ns~l-t~di~t ratio we report is higher than might be expected from anatomical estimates of the overatt proportion of uncrossed to crossed optic fibers in the rat
In the third series the camera recorded the diameter of the right eye as it was stimuiated, providing a measure of the direct PLR
Summary
In virtually all vertebrates the pupil of the eye degree of binocularity and no consensual PLR constricts in response to increased illumination whatsoever. Animals such as the pigeon of the retina (Walls, 1967). Certain rays exhibit little bin~ula~ty and and in some other animals, the pupil constricts no uncrossed optic fibers and yet exhibit a in response to increased illumination of the consensual PLR. The literature contains reres~ctively, comprise what is known as the ports convicting with this rule For the first time, the magnitude of the consensual PLR as compared to the direct PLR in this animal, under conditions wherein the influence of stray light can be carefully assessed
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