tokens: In a microdialysis study , 10 muL of saline ( group C ; n = 8 ) or 30 mug of morphine ( group M ; n = 8 ) was injected intrathecally ( IT ) 0 . 5 h after reflow , and 30 mug of morphine ( group SM ; n = 8 ) or 10 muL of saline ( group SC ; n = 8 ) was injected IT 0 . 5 h after sham operation .