Anesthesia-induced neurodegeneration in fetal rat brains

Abstract

We investigated the extent of isoflurane-induced neurodegeneration on the fetuses of pregnant rats exposed in utero. Pregnant rats at gestational d 21 were divided into three experimental groups. Rats in the control group spontaneously breathed 100% oxygen for 1 h. Rats in the treatment groups breathed either 1.3 or 3% isoflurane in 100% oxygen through an endotracheal tube, with mechanical ventilation for 1 h. Rat pups were delivered by cesarian section 6 h after treatment, and fetal blood was sampled from the left ventricle of each fetal heart and evaluated for S100beta. Fetal brains were then evaluated for apoptosis, using caspase-3 immunohistochemistry in the CA1 region of the hippocampus and the retrosplenial cortex (RS). The 3% isoflurane treatment group showed significantly higher levels of S100beta levels and significantly increased average densities of total caspase-3-positive cells in the CA1 hippocampus and RS cortex compared with the control and the 1.3% isoflurane groups. There were no differences in S100beta levels or densities of caspase-3-positive cells between the control and 1.3% isoflurane groups. Isoflurane at a concentration of 3% for 1 h increased neurodegeneration in the hippocampal CA1 area and the retrosplenial cortex in the developing brain of fetal rats.

Figures

Figure 1

Nomogram illustrating distribution of pregnant mothers and their fetuses among different experimental groups.

Figure 2

Changes of mean arterial blood pressure (MAP) during the treatment of isoflurane at different concentrations. Solid circle, 3% isoflurane; open square, 1.3% isoflurane. N=6 for each time point.

Figure 3

Isoflurane at high concentration (3%) increased S100β in the rat fetal blood. S100β levels in the blood obtained from left ventricle puncture were determined using a Sangtic 100 ELISA kit. ISO, isoflurane. Data represent mean±SE from 12 rat fetus. * P<0.05 compared to both control and 1.3% ISO.

Figure 4

In utero isoflurane at high concentration (3%) increased apoptosis in the hippocampus CA1 region of the fetal developing brains. A. Arrows indicate caspase-3 positive cells in the hippocampus CA1 region located within the red rectangles illustrated on the left demonstrating the entire hippocampus of developing fetal brains at low magnification. Scale bar=50 µm for the low magnification on the left and 10 µm for the high magnification on the right (Red bar on the right lower corner for each picture). B. Data represents the mean±SE of 12 fetal rat brains from 6 pregnant mothers (N=6) in either the control group or the treatment groups with 1.3% or 3% isoflurane (ISO). * P<0.05 compared to both control and 1.3% ISO, N=6.

Figure 5

In utero isoflurane at high concentration (3%) increased apoptosis in the retrosplenial cortex of the fetal developing brains. A. Arrows indicate caspase-3 positive cells in the retrosplenial cortex in different experiment groups. B. Data represents the mean±SE of 12 fetal rat brains from 6 pregnant mothers (N=6) in either the control group or the treatment groups with 1.3% or 3% isoflurane (ISO). Scale bar=10 µm (Red bar on the right lower corner for each picture). ** P<0.001 compared to both control and 1.3% ISO, N=6.