Albeit apoptosis is observed in pathological conditions, a large number of cells which are involved in the development of central nervous system also undergo physiological apoptotic process in fetus. Hypotensive episodes in the course of pregnancy are frequent cause of circulatory failure in the fetus, thus it may represent a potential risk for hypoxic ischemic injury in fetal brain as well. Cellular injury after hypoxic-ischemic insult is caused by necrosis and/or apoptosis. Neuronal death depends on the severity and the site of the injury as well as the time after injury. This study was aimed to explore the early term (within 24 hours) effects of maternal transient systemic hypotension on the development of fetal brain in rats.

Thirty pregnant Sprague-Dawley rats (3-6 months old) were included in the study. On the 15^th day of pregnancy, rats were subjected to either transient systemic hypotension (hypotension group, n=15) by blood withdrawal for 30 minutes or sham operation (control group, n=15). Two randomly selected fetuses were taken after cesarean section under ketamine/xylazine anesthesia in each rat both in hypotension and control groups after 6 hr or 12 hr or 24 hr (n=5 pregnant rats in each time points). Brain sections were stained with hematoxylin-eosine (HE). Apoptosis was evaluated in fetal brain sections both by TUNEL Method and caspase-3 staining. TUNEL (+) and caspase-3 (+) cells were counted and scored double-blindly.

HE staining did not reveal any morphological difference between hypotension and control groups. TUNEL (+) cells were more abundant in hypotension group at all three time points than in the corresponding control group (P<0.05). The most prominent increase was seen in the 12 hr group (P<0.05). In accord with our findings with TUNEL Method, caspase-3 (+) cells were more prominent in the hypotension group at all three time points when compared with the corresponding control group (P<0.05). The most prominent increase in caspase-3 (+) staining was detected in the 12 hr hypotension group when compared to other time points.

Maternal transient systemic hypotension caused a significant increase in apoptosis in fetal rat brain mainly at 12 hr, which may have a potential significance of the timing of neuroprotective agents against brain damage.