A combined behavioral and morphological study on the effects of fetal asphyxia on the nigrostriatal dopaminergic system in adult rats

Fetal asphyxic insults in the brain are known to be associated with developmental neurological problems like neuromotor disorders. However, little is known about the long-term consequences of fetal asphyxia (FA). For that reason, the present study investigated the long-term effects of FA on motor behavior and dopaminergic circuitry. FA was induced at embryonic day 17 by 75-minute clamping of the uterine circulation. SHAM animals underwent the same procedure except for the clamping. This was followed by full-term vaginal delivery of animals in all groups (FA, SHAM and untreated controls). At 6 months, basal and amphetamine-induced locomotor activity was measured during open field testing. Brain sections were stained for tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP). TH-positive cells and GFAP-positive cells in substantia nigra pars compacta (SN_C) and striatum were counted using design-based stereology. Moreover, TH-immunoreactivity in the striatum was assessed by grey value measurements. Behavioral analysis demonstrated that SHAM and FA showed less basal and amphetamine-induced activity than controls. Histochemically, FA decreased the number of TH-positive neurons in the SN_C and lowered TH-positive in the striatum. Furthermore, more GFAP-positive cells were found in the SN_C and striatum in FA than in either control and SHAM groups. Additionally, FA animals showed ventriculomegaly associated with smaller white matter as well as grey matter volumes. The data show that FA was associated with deficits in both dopamine-related motor behavior and biochemistry. These alterations were associated with nigrostriatal astrogliosis. The present study demonstrates the sensitivity of the dopaminergic system towards FA.