[Rectal dexmedetomidine in rats: evaluation of sedative and mucosal effects]

In this study, we investigated the anesthetic and mucosal effects of the rectal application of dexmedetomidine to rats.

Male Wistar albino rats weighing 250-300g were divided into four groups: Group S (n=8) was a sham group that served as a baseline for the normal basal values; Group C (n=8) consisted of rats that received the rectal application of saline alone; Group IPDex (n=8) included rats that received the intraperitoneal application of dexmedetomidine (100μgkg(-1)); and Group RecDex (n=8) included rats that received the rectal application of dexmedetomidine (100μgkg(-1)). For the rectal drug administration, we used 22G intravenous cannulas with the stylets removed. We administered the drugs by advancing the cannula 1cm into the rectum, and the rectal administration volume was 1mL for all the rats. The latency and anesthesia time (min) were measured. Two hours after rectal administration, 75mgkg(-1) ketamine was administered for intraperitoneal anesthesia in all the groups, followed by the removal of the rats' rectums to a distal distance of 3cm via an abdominoperineal surgical procedure. We histopathologically examined and scored the rectums.

Anesthesia was achieved in all the rats in the Group RecDex following the administration of dexmedetomidine. The onset of anesthesia in the Group RecDex was significantly later and of a shorter duration than in the Group IPDEx (p<0.05). In the Group RecDex, the administration of dexmedetomidine induced mild-moderate losses of mucosal architecture in the colon and rectum, 2h after rectal inoculation.

Although 100μgkg(-1) dexmedetomidine administered rectally to rats achieved a significantly longer duration of anesthesia compared with the rectal administration of saline, our histopathological evaluations showed that the rectal administration of 100μgkg(-1) dexmedetomidine led to mild-moderate damage to the mucosal structure of the rectum.