The effect of ethanol on habituation and the cardiovascular response to stimulation in fetal sheep.

Fetal cardiovascular (CVS) changes, forelimb movements (FM) and rates of habituation to repeated stimulation, with suffusions of cold saline over the skin, were measured in 12 chronically catheterized fetal sheep aged 130-145 days. Stimulation of the fetuses caused a significant rise in heart rate (HR) (p less than 0.01) and blood pressure (BP) (p less than 0.001) and FM (p less than 0.01). When the ewe was given an intravenous (i.v.) infusion of ethanol which produced fetal ethanol levels of 87 +/- 1.1 mg/100 ml, the number of spontaneous FM decreased (p less than 0.05). After i.v. ethanol, repeated stimulation of the fetuses still caused an increase in FM (p less than 0.01) and a rise in HR (p less than 0.05) and BP (p less than 0.02) but the fetuses habituated more rapidly (7.25 +/- 1.28 stimuli) compared to control experiments performed prior to (21.5 +/- 3.57 stimuli) or after the ethanol (17.75 +/- 5.83, p less than 0.01). Fetal exposure to low concentrations of ethanol does affect the patterns of response and habituation of the developing fetal central nervous system.