Effects of the Olfactory Bulbs on the Activity of Reticular Neurons of the Bulbar Respiratory Center in Hypoxia

Abstract

The study reported here seeks to explain the roles of different limbic system formations in controlling respiration in conditions of oxygen insufficiency. The effects of stimulation of the olfactory bulbs (OB) on medulla oblongata respiratory center (RC) neurons during exposure to hypoxia were studied in a laboratory barochamber. Stimulation of the OB in normoxia had a predominantly activatory influence on the baseline activity of neurons. During hypoxia, the responses of medulla oblongata respiratory center neurons to stimulation of the OB were phasic in nature. At the first stage of hypoxia (at an altitude of 4000–5000 m), on the background of hypoxic activation of neurons, the activatory influence of this formation on the spike activity of neurons persisted, albeit weakly. At an altitude of 7500–8000 m, (severe hypoxia phase), on the background of hypoxic suppression of medulla oblongata neuron activity and respiration overall, the activatory effect of stimulation of the OB on the spiked activity of neurons in the bulbar respiratory center was more marked than in the first stage. The results of these experiments provide grounds for the suggestion that the OB is among the limbic system formations with predominantly activatory influences on RC neurons. After lowering the animals to normal atmospheric pressure, there was gradual restoration of initial values for both baseline neuron activity and their responses to stimulation.