Effects of voluntarily-ingested buprenorphine on plasma corticosterone levels, body weight, water intake, and behaviour in permanently catheterised rats.

This study investigated the peri- and postoperative effect of pre-emptive analgesia through voluntary ingestion of buprenorphine in Nutella, in male Sprague-Dawley rats. An arterial catheter was inserted and the rats were connected to an automated blood sampling device (AccuSampler). Blood samples were drawn up to 18 h after surgery and the plasma concentrations of corticosterone were quantified. Postoperative changes in water intake and body weight were recorded, and the behaviour of the rats was analysed during two 30-min periods. Pre-emptive oral buprenorphine treatment reduced the plasma corticosterone levels in the postoperative period, compared to controls treated with local anaesthetics. Buprenorphine-treated rats consumed more water and maintained body weight better. Behavioural observations indicated that buprenorphine changed the behaviour in non-operated rats but there was no difference in the operated rats. The present study strengthens the hypothesis that pre-emptive oral buprenorphine in Nutella is suitable for treatment of postoperative pain in rats.