Background: Our previous research showed that 4 h of maternal anesthesia with isofurane during early gestation in
pregnant rats leads to a defcit in spatial memory of adult male ofspring. Because spatial memory is predominantly a
hippocampally-mediated task, we asked the question if early gestational exposure to isofurane afects development
of the hippocampus in the ofspring.
Findings: Previously behaviorally characterized adult male rats that were exposed to isofurane during second
trimester were sacrifced at 4 months of age (N = 10 and 13, control and isofurane groups, respectively) for quantitative histology of hippocampal subregions. Sections were stained with cresyl violet and the total number of cells in
the granular layer of the dentate gyrus and the pyramidal cell layer in the CA1 region were determined by a blinded
observer using unbiased stereological principles and the optical fractionator method. Data were analyzed using
Student’s t test; P < 0.05 was accorded statistical signifcance. Stereological examination revealed 9% fewer cells in
the granular layer of the dentate gyrus of isofurane-exposed adult rats compared to controls (1,002,122 ± 84,870 vs.
1,091,829 ± 65,791, respectively; Mean ± S.D, *P = 0.01). In contrast, there were no changes in the cell number in the
CA1 region, nor were there changes in the volumes of both regions.
Conclusions: Our results show that maternal isofurane anesthesia in rodents causes region-specifc cell loss in the
hippocampus of adult male ofspring. These changes may, in part, account for the behavioral defcits reported in adult
rats exposed to isofurane in utero.

• Behavioral and Brain Functions