Isoflurane exposure leads to apoptosis of neurons and oligodendrocytes in 20- and 40-day old rhesus macaques

- Following 5 h of isoflurane anesthesia, brains of P20 and P40 rhesus macaques demonstrated similar levels of both neuronal apoptosis and oligodendrocyte apoptosis.
- The P20 and P40 rhesus macaques exposed to isoflurane had 3.6 times as many apoptotic cells (neurons + oligodendrocytes) as the control animals that were not exposed to anesthesia.
- In the P20 and P40 rhesus macaques exposed to isoflurane, approximately 66% of the apoptotic cells were oligodendrocytes and 34% were neurons.

Previously we reported that a 5-hour exposure of 6-day-old (P6) rhesus macaques to isoflurane triggers robust neuron and oligodendrocyte apoptosis. In an attempt to further describe the window of vulnerability to anesthetic neurotoxicity, we exposed P20 and P40 rhesus macaques to 5 h of isoflurane anesthesia or no exposure (control animals). Brains were collected 3 h later and examined immunohistochemically to analyze neuronal and glial apoptosis. Brains exposed to isoflurane displayed neuron and oligodendrocyte apoptosis distributed throughout cortex and white matter, respectively. When combining the two age groups (P20 + P40), the animals exposed to isoflurane had 3.6 times as many apoptotic cells as the control animals. In the isoflurane group, approximately 66% of the apoptotic cells were oligodendrocytes and 34% were neurons. In comparison, in our previous studies on P6 rhesus macaques, approximately 52% of the dying cells were glia and 48% were neurons. In conclusion, the present data suggest that the window of vulnerability for neurons is beginning to close in the P20 and P40 rhesus macaques, but continuing for oligodendrocytes.