[Effect of analgestics and narcotics on the potentials of the posterior roots evoked by stimulation of the sensorimotor cortex].

Experiments set up on unanesthetized, curarized cats demonstrated that sodium oxybutyrate in doses of 75--200 mg/kg and nembutal in doses of 5--20 mg/kg prolong the duration of corticospinal posterior roots potentials (PRP). The initial effect of morphine and promedol in doses of 1--3 and 0.5--1 mg/kg, respectively was not only a longer duration (by 30--40 msec), but also a higher amplitude of the PRP, evoked by the stimulation of the sensomotor cortex. Phentanyl used in a dose range of 0.01 to 0.06 mg/kg did not produce any changes in the descending PRP. Anesthetics (sodium oxybutyrate, nembutal, ether) and analgesics (morphine, phenadon) inhibited the corticospinal PRP, when used in large doses.