Fig. 4. Exposure time-dependent effects of desflurane on dendritic spines. Representative confocal images (3D volume rendering) showing dendritic shafts and spines from control animals (A ) and those exposed to desflurane for 0.5 h (B ), 1 h (C ), and 2 h (D ). E , Quantitative analysis of dendritic spine density on apical and basal dendrites shows an exposure time-dependent increase in dendritic spine density. F , Frequency-distribution histogram of spine head diameter shows that the sevoflurane-induced increase in spine density is primarily due to an increase in the number of spines with small heads. Three animals per age group were used to determine spine density. Results are expressed as mean ± SD, n = 3 animals per group. A total of 3,631 spines for apical and 2,974 spines for basal dendrites were counted to determine spine density. For spine head diameter distribution, a total of 1,205 spines from eight randomly selected cells from three animals per group were analyzed. One-way analysis of variance with Bonferroni post hoc  tests were used for searching statistical difference between age groups. *P < 0.05; ***P < 0.001. Correction bar: 5 μm.