Reduced soma size of the M-neurons in the lateral geniculate nucleus following foetal alcohol exposure in non-human primates

Visual impairment is commonly reported as a consequence of heavy prenatal ethanol exposure in humans. Children generally display characteristic cranio-facial dysmorphology and represent typical severe cases of foetal alcohol syndrome. Binge-like rodent model systems have concluded that third trimester equivalent ethanol exposure results in widespread apoptosis in the visual system from the retina to the visual cortex. Neither clinical nor animal studies address the consequences of more moderate prenatal ethanol exposure on the visual system. The current study uses a naturalistic and voluntary consumption approach in non-human primates (Chlorocebus sabeus) in order to more closely model prenatal ethanol consumption patterns in humans. Pregnant vervet monkeys voluntarily drank on average 2.418 ± 0.296 g etoh/kg/day four times a week during the third trimester. Using unbiased stereology, we estimated the neuronal and glial population of the parvocellular (P) and magnocellular (M) layers of the lateral geniculate nucleus (LGN) following foetal alcohol exposure (FAE) in infant subjects. Layer volume and total number of neurons and glia in the LGN of the FAE subjects were not significantly different from age-matched control subjects. The M neuronal soma size of FAE subjects, however, was significantly reduced to resemble the size of the P-neurons. These results suggest that alterations at the level of morphology and anatomy of the M-neurons may lead to behavioural deficits associated with the integrity of the dorsal visual pathway.