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June 1980

Delayed Maze-Learning in Rats After Prenatal Exposure to Clorazepate

Arch Neurol. 1980;37(6):350-351. doi:10.1001/archneur.1980.00500550052005

• Five pregnant Long-Evans rats were given 32 mg/kg of body weight of clorazepate dipotassium (Tranxene) intramuscularly on gestational days 8.5, 9.5, and 10.5. Five control mothers received sterile water. The control group of offspring (N = 19) and the experimental group (N = 20) were compared by means of a timetable for neurologic development and for maze learning ability. Although the experimental group was significantly slower in stomach-lifting and walking, the neurologic battery as a whole did not disclose any consistent difference. At 21 days of age, the experimental rats weighed significantly more than the control rats. The control rats learned the maze significantly faster than the experimental rats. On trials 10 to 14, the control group ran the maze in less than half of the time of the experimental group. The study emphasizes the need to include tests of cerebral function in addition to developmental reflexes to screen for subtle effects of teratogens, which the simpler developmental tests may miss.