Effects of prior experience and 'functional disturbance' on acute and chronic tolerance to methylphenidate.

The degree of habituation or adaptation an animal has experienced prior to the administration of methylphenidate was found to be more crucial in determining the animal's response to the drug than chronic drug administration alone. Rats allowed to adapt in a Y-maze for 24 days showed less methylphenidate-induced activity than animals receiving chronic administration of saline or methylphenidate but no adaptation, when animals were injected with the drug and tested in the Y-maze on Day 25. Animals also were shown to develop tolerance to the methylphenidate-induced activity.