Neonatal binge ethanol exposure using intubation: timing and dose effects on place learning.

Abstract

Neonatal rats were given ethanol using an acute intubation procedure that resulted in daily binge-like exposure with minimal effects on somatic growth. Acquisition of place learning in the Morris water maze was evaluated on postnatal days (PD) 26-31. In Experiment 1, a total of 5.25 g/kg/day of ethanol was administered in two daily intubations on PD 4-6, PD 7-9, or PD 4-9, producing mean peak BACs of 265 mg/dL. Place learning acquisition deficits in a 114-cm-diameter tank were found for the PD 4-9 and PD 7-9 groups, but not the PD 4-6 group. In Experiment 2, either 4.5 or 5.25 g/kg/day of ethanol was administered on PD 7-9 and place learning was tested in a 171-cm-diameter tank. Significant acquisition deficits resulted from the higher dose, and probe trial search patterns for both ethanol groups were significantly less localized than controls. In Experiment 3, no significant effects of either PD 7-9 dose were found on a visible platform task. These findings reveal selective place learning deficits in this intubation model of neonatal binge exposure, and confirm a temporal window of vulnerability to spatial learning deficits during the second neonatal week.