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This study was designed to investigate the effect of early thyroxine (T4) treatment on the development of the Purkinje cells in fetal rats exposed to alcohol.Time-pregnant SD rats were divided into alcohol and control groups on the 6th day of gestation.Alcohol group rats (n =12) received 35 calories of liquid alcohol diet every day;control group rats (n =6) were fed a liquid diet in which milk replaced alcohol isocalorically;after the offspring were born,rats in the alcohol group were subdivided into alcohol and alcohoi+ T4 groups.The alcohol + T4 group pups were subcutaneously administered exogenous thyroxine (5 μg/kg per day) from postnatal day 1 (P1) to PI0.At P7,P14,P21,P28,pup body weights of the alcohol,control,and alco-hol + T4 groups were measured,and plasma thyroxine concentrations were determined.The distributions of brain-derived neurotrophic factor (BDNF)-and its receptor tropomyosin-related kinase B (TrkB)-immunoreactive Purkinje cells were de-termined by immunohistochemical staining.Pup body weights in the alcohol + T4 and control groups in each period were significantly higher than in the alcohol group (P < 0.05).T4 concentrations in the alcohol + T4 and normal groups in each period were significantly higher than in the alcohol group (P < 0.05).In the alcohol + T4 and control groups,the neatly ar-ranged and dyed bright BDNF-and TrkB-immunoreactive Purkinje cells were obviously observed in the rat cerebellar cortex on the 7th day after birth;and on the 28th day after birth,the numbers of BDNF-and TrkB-immunoreactive Purkinje cells in the alcohol + T4 group were greater than in the control group,with more orderly arrangement,longer projection and some visible branches.These findings suggest that early T4 treatment can reduce weight loss and increase blood low thyroid hor-mone level in fetal alcohol-exposed rats,which is able to promote the synthesis of BDNF in the brain of early postnatal rats and contribute to the development of BDNF-and TrkB-positive neurons,improving the neurological developmental disor-der caused by alcohol exposure in the fetal period.