THE EFFECT OF THIOPENTAL AND CYANIDE ON THE ACTIVITY OF INSPIRATORY NEURONS

¹ Merck Institute for Therapeutic Research, West Point, Pennsylvania

The activity of single inspiratory neurons in time ventrolateral medulla of the decerebrate cat has been studied with indium microelectrodes. The duration of the burst of neuronal activity, the number of spike discharges per burst, the interval between the bursts and the frequency of time neuronal discharge were measured as well as the amplitude and rate of respiration.

Control studies showed that none of the paranmeters of inspiratory neuronal activity measured varied more than ± 10% from control values over a 30-minute period. The effect of thiopental (5 mg/kg) on the activity of inspiratory neurons was to increase the duration of the burst, the number of spike discharges per burst and the interval between the bursts, while time frequency of neuronal discharge was decreased. The rate and amplitude of respiration were depressed.

The effect of sodium cyanide (0.09 mg/kg) on the inspiratory neuronal activity was to shorten the duration of the burst of activity and the interval between the bursts and to increase the number of spikes per burst and time frequency of discharge. Cyanide produced an increase in the rate and amplitude of respiration.

There was an inverse relationship between the duration of the burst of activity and the rate of respiration and a direct relationship between frequency of neuronal activity and amplitude of respiration.