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Brett G. Jeffrey, Martha Neuringer; Age-Related Decline in Rod Phototransduction Sensitivity in Rhesus Monkeys Fed an n-3 Fatty Acid–Deficient Diet. Invest. Ophthalmol. Vis. Sci. 2009;50(9):4360-4367. doi: 10.1167/iovs.09-3640.
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purpose. Docosahexaenoic acid (DHA), an n-3 fatty acid, is the major polyunsaturate in rod outer segments. The effect of long-term n-3 fatty acid deficiency on rod and cone phototransduction was investigated in the rhesus monkey.
methods. From birth to ≅9 years rhesus monkeys were fed an n-3–deficient diet (n = 9) known to reduce retinal DHA by 80%. Monkeys in the control group (n = 12) received either 8% α-linolenic acid (ALA) or 0.6% DHA, both of which support normal retinal DHA levels. None of the diets contained carotenoids. Photoactivation kinetics were assessed from the rate of increase and a P3 model fit of the ERG a-wave. Maximal cone amplitude and sensitivity were measured from the cone a-wave at 4 ms. The rod photoresponse and rod recovery were derived by using a paired flash method.
results. Rod sensitivity was reduced by 40% in the n-3–deficient monkeys at 9 but not 4.5 years. The onset of the rising phase of the photoresponse was significantly delayed (P < 0.004) at 9 years. Rod recovery was delayed by 20% in n-3–deficient monkeys at both ages, but only for bright saturating flashes. Cone phototransduction was not altered by n-3 deficiency.
conclusions. Long-term dietary n-3 deficiency in the rhesus monkey was associated with two changes in retinal function. First, there was a delay in rod recovery that has remained relatively constant throughout life. Second, there was an age-dependent loss in rod phototransduction sensitivity; the lack of dietary carotenoids may have contributed to this decline.
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