Tolerance in methylphenidate-induced locomotion in prairie dogs (Cynomys ludovicianus).

After a five-day adaptation period in activity wheels, four prairie dogs were assigned to a methylphenidate group (2.5 mg/kg, s.c.) and four prairie dogs were assigned to a saline group for ten consecutive daily injections. Half-revolutions of locomotor activity were recorded during seven measurement periods taken daily. During the third measurement period, from 1-3 hrs following injection, the methylphenidate group declined in locomotor activity over the first three days of drug administration.