tokens: Compared with sham - operated controls , lesions significantly ( p < 0 . 25 ) blunted the early ( < 60 min ) free - field locomotor hypoactivity caused by nicotine ( 0 . 5 mg kg ( - 1 ) , i . m . ) , enhanced the later ( 60 - 120 min ) nicotine - induced hyperactivity , and raised spontaneous nocturnal activity .