Anesthesia was induced with intravenous ( IV ) propofol ( 4mgkg ( -1 ) minute ( -1 ) ) and maintained with propofol starting at 0.4 mgkg ( -1 ) minute ( -1 ) ( PRO , n = 4 ) or IV tiletamine-zolazepam ( 5mgkg ( -1 ) ) and maintained with supplementary doses of TZ ( TZ , n = 4 ) .