Neonatal Ethanol Exposure Impairs Eyeblink Conditioning in Weanling Rats

Eyeblink conditioning depends on an identified brainstem-cerebellar circuit and may be useful in functional studies of early cerebellar damage produced by neurotoxicants. The present study asked whether binge-like neonatal ethanol exposure that damages the cerebellum would also result in eyeblink conditioning deficits. On postnatal day (PND) 23 to PND24, three groups of Long-Evans rat pups were tested for eyeblink conditioning: (1) ETOH, a group that received intragastric administration of 5.25 g/kg/day of ethanol on PND4 through PND9 via artificial rearing; (2) GC, a gastrostomy control group that received calorically matched milk formula on those days; and (3) SC, suckle controls that were reared normally with their dams. Eyeblink conditioning was severely impaired in the ethanol-treated group relative to the GC and SC groups, which did not differ. This impairment did not reflect sensory, motor, or motivational effects of ethanol treatment, because startle responses to the auditory conditioned stimulus and reflexive eyeblink responses to the unconditioned stimulus did not differ across the three treatment groups. These results suggest that neonatal binge ethanol exposure disrupted brain development in a manner that selectively impaired associative processes involved in eyeblink conditioning, consistent with alcohol-induced damage to the brainstem-cerebellar circuit necessary for this form of learning.