Reproduction of repetitive stimulation of the medulla by the respiratory center

Abstract

The tidal volume of respiration, activity of respiratory neurons or the intercostal muscles, and the electromyogram of the diaphragm were recorded in cats anesthetized with nembutal in response to stimulation of different points in the medial zone of the respiratory center. Periodic stimulation of this zone with a period θ, differing from the period of respiration T of the preparation under normal conditions, sets new rhythms of activity in the respiratory system. The ratio of stable respiration rate during stimulation may be 1∶1 or 2∶1, and sometimes even 3∶1 to the imposed stimulation rhythm. For all stimulation points investigated, stable reproduction of the rhythm is accompanied by preservation of the initial tidal volume. The independence of rhythm setting on vagal afferentation and also on the CO₂ level in the inspired air, established experimentally, suggests that connections between neurons belonging to systems of the lateral and medial zones and, probably, connections between these zones and neurons in the pons play a crucial role in these effects.