Table 2

i.c.v. bolus doses of oxycodone, morphine, or saline (control rats) administered to naive, oxycodone-tolerant, and morphine-tolerant adult male DA rats2-a

Treatment Period 1: Naive RatsTreatment Period 2: Tolerant RatsTreatment Period 3: Tolerant Rats
Oxycodone i.v. infusion 2.5 mg/24 h for 60 hi.c.v. bolus dose of morphinei.c.v. bolus dose of oxycodone
 18 nmol (n = 5) 44 nmol (n = 5)
 34 nmol (n = 5) 78 nmol (n = 5)
 55 nmol (n = 5) 132 nmol (n = 5)
 150 nmol (n = 5) 300 nmol (n = 5)
Morphine i.v. infusion 10 mg/24 h for 60 hi.c.v. bolus dose of oxycodonei.c.v. bolus dose of morphine
 44 nmol (n = 5) 18 nmol (n = 5)
 78 nmol (n = 5) 34 nmol (n = 5)
 132 nmol (n = 5) 55 nmol (n = 5)
 300 nmol (n = 5) 150 nmol (n = 5)
 225 nmol (n = 4)
i.c.v. bolus dose of oxycodone
 22 nmol (n = 4)
 44 nmol (n= 5)
 78 nmol (n = 6)
 132 nmol (n = 5)
i.c.v. bolus dose of morphine
 18 nmol (n = 5)
 34 nmol (n = 5)
 55 nmol (n = 5)
 150 nmol (n = 4)
i.c.v. bolus dose of saline (n = 4)
  • 2-a  Each treatment period was followed by a 12-h washout period with saline.