Effects of binge ethanol exposure during first-trimester equivalent on corticothalamic neurons in Swiss Webster outbred mice

Fetal alcohol spectrum disorders range in severity depending on the amount, timing, and frequency of alcohol exposure. Regardless of severity, sensorimotor defects are commonly reported. Sensorimotor information travels through three tracts of the internal capsule: thalamocortical axons, corticothalamic axons, and corticospinal axons. Here we describe the effects of binge ethanol exposure during the first-trimester equivalent on corticothalamic neurons using Swiss Webster mice. We injected pregnant mice with ethanol (2.9g/kg, intraperitoneal, followed by 1.45g/kg, intraperitoneal, 2h later) on embryonic days (E) 11.5, 12.5, and 13.5. Our paradigm resulted in a mean maternal blood ethanol content of 294.8 +/- 15.4mg/dl on E12.5 and 258.3 +/- 22.2mg/dl on E13.5. Control dams were injected with an equivalent volume of PBS. Bromodeoxyuridine birthdating was carried out on E11.5 to label S-phase neurons. The days of injection were chosen because they are at the onset of neurogenesis and axon extension for corticothalamic, thalamocortical, and corticospinal neurons. Ethanol-exposed pups exhibited no differences compared with controls on day of birth in litter size, body weight, or brain weight. Corticothalamic neurons labeled with bromodeoxyuridine and T-box brain 1 were located in the deep layers of the cortex and did not differ in number in both groups. These results contrast several studies demonstrating alcohol-related differences in these parameters using chronic ethanol exposure paradigms and inbred mouse strains. Therefore, our findings highlight the importance of expanding the mouse strains used to model fetal alcohol spectrum disorder to enhance our understanding of its complex etiology.