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Use of a Cross-over Design in Testing Short-Term Methylphenidate Effects on Avoidance Conditioning

90 albino rats, equally divided between the sexes, were divided into groups which received dosages of 4.5 mg/kg, 13.5 mg/kg of methylphenidate and equal volume of distilled water for a total of 8 days. After the initial training period a third of the subjects continued with the same administration while the remaining two-thirds of the animals received the other two dosage combinations. Short-term administration of methylphenidate (Ritalin) facilitated learning as measured by avoidance conditioning. The cross-over design presents advantages over other experimental designs in assessing a variety of possible drug effects. No relationship was obtained between dosage level and response acquisition. However, a linear dose-response relationship was obtained on activity level.