Isoflurane exposure in newborn rats induces long-term cognitive dysfunction in males but not females.
Volatile anesthetics are used widely for achieving a state of unconsciousness, yet these agents are incompletely understood in their mechanisms of action and effects on neural development. There is mounting evidence that children exposed to anesthetic agents sustain lasting effects on learning and memory. The explanation for these behavioral changes remains elusive, although acute neuronal death after anesthesia is commonly believed to be a principal cause. Rodent models have shown that isoflurane exposure in newborns induces acute neuroapoptosis and long-term cognitive impairment. However, the assessment of predisposing factors is lacking. We investigated the role of sex by delivering isoflurane to postnatal day (P)7 male and female Sprague Dawley rats for 4 h. Brain cell death was assessed 12 h later using FluoroJade C staining in the thalamus, CA1-3 regions of hippocampus, and dentate gyrus. Behavior was assessed separately using a series of object recognition tasks and a test of social memory beginning at P38. We found that isoflurane exposure significantly increased neuronal death in each brain region with no difference between sexes. Behavioral outcome was also equivalent in simple novel object recognition. However, only males were impaired in the recognition of objects in different locations and contexts. Males also exhibited deficient social memory while females were intact. The profound behavioral impairment in males relative to females, in spite of comparable cell death, suggests that males are more susceptible to long-term cognitive effects and this outcome may not be exclusively attributed to neuronal death.
Department of Anesthesia and Perioperative Care, University of California, San Francisco, 513 Parnassus Ave., Box 0542, Med Sci S261, San Francisco, CA 94143, USA.
Bradley H
BH
Lee
Department of Anesthesia and Perioperative Care, University of California, San Francisco, 513 Parnassus Ave., Box 0542, Med Sci S261, San Francisco, CA 94143, USA.
John Thomas
JT
Chan
University of Arizona College of Medicine, 550 E Van Buren St., Phoenix, AZ 85004, USA.
Ekaterina
E
Kraeva
University of Rochester, 500 Wilson Blvd., Rochester, NY 14627, USA.
Katherine
K
Peterson
Department of Anesthesia and Perioperative Care, University of California, San Francisco, 513 Parnassus Ave., Box 0542, Med Sci S261, San Francisco, CA 94143, USA. Electronic address: sallj@anesthesia.ucsf.edu.
Jeffrey W
JW
Sall
D018685:Anesthetics, Inhalation / Q000633:toxicity*; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D003072:Cognition Disorders / Q000139:chemically induced* / Q000473:pathology; D005260:Female; D007530:Isoflurane / Q000633:toxicity*; D007858:Learning / Q000187:drug effects; D008297:Male; D008568:Memory / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors
D018685:Anesthetics, Inhalation; D007530:Isoflurane
Anesthetics; Isoflurane; Memory; Sex; Toxicity