Effect of electrical stimulation of the medullary respiratory neurons on respiratory air flow in cats. New findings on expiratory neurons.

Respiratory air flow during electrical stimulation of the medullary respiratory neurons was measured in 25 sodium pentobarbital-anesthetized cats. The effect of variation of stimulus parameters on the air flow was studied too. The medullary respiratory neurons were localized by exploring the medulla with microelectrodes. The inspiratory neurons were found hetween 2 and 4 mm lateral to the midline, and from the level of the obex to 4 mm rostrally in the ventral reticular formation. The expiratory cells were between 2 and 3 mm lateral to the midline, extending from the level of the obex to 3 mm caudally, slightly less ventral than the inspiratory neurons. The maximal inspiratory and expiratory flow rates were 56 and 44 liters per minute respectively when the respiratory neurons were stimulated with a stimulus of 4 volts and 200 Hz/sec., while duration of the stimulating pulse was 0.5 millisecond. In general, the increase in air flow was proportional to the magnitude of the stimulus strength, stimulus frequency and duration of the stimulating pulse.