Chloramphenicol administration during brain development: impairment of avoidance learning in adulthood.

Rats treated with chloramphenicol from days 7 to 21 of intrauterine life (50 milligrams per kilogram per day, injected subcutaneously into the mothers) or in the first 3 days of extrauterine life (50 to 100 milligrams per kilogram per day) were trained for avoidance conditioning when 60 days old. The acquisition of the avoidance response was impaired to a highly significant degree in all the treated groups.