Effects of ketamine (CI 581) on cell responses to cutaneous stimulations in laminae IV and V in the cat's dorsal horn

Abstract

The cells of laminae IV and V in the dorsal horn of the spinal cord are probably involved in the transmission of nociceptive messages to the upper centers. Pharmacological studies have shown that the analgesic proporties of some drugs could have their origin in the depression of synaptic transmission at this level. Therefore, the effect of ketamine on the activity of the laminae IV and V units was studied in spinal cats. Ketamine, 2–10 mg/kg, i.., did not modify significantly the spontaneous firing of the lamina IV cells, or their response to light cutaneous stimulations. Similarly, responses of the lamina V units to light stimulations (touch, hair movements, pressure) were not affected, while responses to nociceptive stimulations (pinching, strong electrical stimulation) were decreased. However, this effect is not sufficient to explain the whole analgesic action of ketamine and other sites of action must be found, sppecially at the subcortical and cortical levels.