[Reaction of respiration neurons in the medulla on locus coeruleus irritation by hypoxia].

Effects of locus coeruleus (LC) stimulation on the impulse activity of bulbar respiration neurons in rats were studied on a background of varying hypoxia. Different levels of hypoxia were used as an experiment model for ensuing summation of the LC effect. At the normal atmospheric pressure, LC electrical stimulation had an alleviating and also inhibiting effect on the impulse activity of these medulla neurons; however, the former effect was dominant. During the initial hypoxia simulating the altitude of 4000-5000 m, LC stimulation had a weak alleviating effect. On this level of hypoxia such effect is highly important, as unchecked strengthening of respiration activating mechanisms may result in excessive hyperventilation and consequent respiration slowing down to standstill because of low blood content of carbonic acid. During heavy hypoxia simulating the altitude of 7500-8000 m LC electrical stimulation had an intrinsic to this structure activating effect on markedly inhibited respiratory neurons. In the event of acute hypoxia the highly sensitive cortical component lose their inhibitory effect on the bulbar respiratory center and suprabulbary formations. However, this favours startup of the activating systems and enhancement of the respiration ventilatory function.