The effects of droperidol and diazepam on the neural excitation of ketamine hydrochloride.

The effects of neuroleptics (droperidol and diazepam) were studied on the neural excitation by ketamine hydrochloride by means of the c-fiber reflex, in the spinal cat and the intact cat. Results can be summarized as follows: 1) Ketamine hydrochloride 125-500 micrograms/Kg i.v. facilitated the neural activity on the c-fiber reflex of the intact cat, but it depressed that of the spinal cat. 2) Droperidol 50-250 micrograms/Kg i.v. and diazepam 50-250 micrograms/Kg i.v. did not influence the neural activity on the c-fiber reflex of the intact cat, but it depressed that of the spinal cat. 3) Droperidol 125 micrograms/Kg i.v. followed by ketamine hydrochloride 125 micrograms/Kg i.v. facilitated the neural activity of the intact cat c-fiber reflex. 4) Diazepam 50 micrograms/Kg i.v. followed by ketamine hydrochloride 250 micrograms/Kg i.v. did not influence the neural activity of the intact cat c-fiber reflex. These data suggested that the neural excitation of ketamine hydrochloride was depressed by diazepam and that a small dose of droperidol did not depress the neural excitation of the intact cat.