Anesthesia-induced Recognition Deficit Is Improved in Postnatally Gonadectomized Male Rats

Preclinical investigations of the effects of general anesthesia on the young brain show differences in vulnerability of males and females to anesthetic exposure at different times during development. However, the mechanism underlying this sex difference is poorly understood. Perinatal testosterone is the primary determinant of sexual differentiation and likely plays an important role in defining the period of susceptibility to anesthetic injury. We investigated whether the removal of testosterone through gonadectomy shortly after birth would improve cognitive outcomes in male rodents after early anesthesia exposure.

Male Sprague Dawley rats underwent gonadectomy at postnatal day 2 (P2), followed by exposure to 6 hours of isoflurane at P7. A control cohort of gonad-intact male littermates was simultaneously exposed. All rats were subjected to a series of object recognition and association tasks beginning at P42. Cell death in the thalamus and hippocampus was assessed in a separate cohort.

All groups performed similarly on the Novel Object Recognition task; however, the gonad-intact isoflurane group exhibited decreased performance in the more difficult tasks. This deficit was ameliorated in the gonadectomized group. Cell death was similar between both isoflurane-exposed groups, regardless of gonadectomy.

The absence of testosterone does not block cell death after anesthesia in specific brain regions of interest; however, does provide some neuroprotection as evidenced by the improved cognitive test performance during adulthood. These findings suggest that testosterone may be mechanistically involved in the sex-specific effects of anesthetic injury on the developing brain by extending the vulnerable period in male rats.