The effects of transcranial electrical stimulation on anaesthesia and analgesia in rats

In this study, we determined the effects of transcranial electrical stimulation (TCES) on the anaesthetic requirements of thiopental and the analgesic requirements of remifentanil, in rats. The experiments were performed on 120 albino male Wistar rats, which were randomly allocated to four groups (n=30). (Thiopental, Thiopental+TCES, Thiopental+Remifentanil, and Thiopental+Remifentanil+TCES). Animals were anaesthetized with thiopental, and 15 min later, remifentanil was injected to rats in the Remifentanil groups. TCES was started in the stimulated groups 20 min after thiopental administration. Rats were stimulated 5 times for this experiment. The times for recovery, herein called Cognition Recovery Time and Motion Recovery Time were measured. Cognition Recovery and Motion Recovery Times were not affected by the stimulation. Analgesia was assessed using the wet tail-flick latency (TFL). In the Thiopental group, the analgesia level returned to control values on the 35th min. In the Thiopental+Remifentanil group, the analgesia level returned to control values on the 50th min. In the Thiopental+ TCES group, the analgesia level reached the peak value on the 65th min. In the Thiopental+Remifentanil+TCES group, the analgesia level reached the peak value on the 35th min and analgesia remained high during the 90 min after cessation of the stimulation. The analgesic potency for the Thiopental+Remifentanil+TCES group was increased by 30-40% when compared with the prior TFL values, 160% when compared with the control group, and 50-75% when compared with Thiopental+TCES group on the 35th min (P<0.001). In conclusion, TCES markedly decreases the anaesthetic and analgesic requirements for thiopental and remifentanil in rats.