Role of Glutamate in the Mechanisms of Adaptation of the System of Respiratory Control in Rats to Intermittent Hypoxia
In experiments on Wistar rats, we studied the role of changes in the state of glutamatergic transmission in the course of adaptation of the system of respiratory control to intermittent hypoxia. The volume/temporal parameters of respiration were estimated according to characteristics of EMG activity (amplitude, integral intensity of EMG discharges) recorded from the diaphragmatic muscle. Changes in EMG activity of the diaphragm induced by acute hypoxia (breathing a 12% О2-containing gas mixture) were estimated before and after of a 14-day-long course of intermittent hypoxia trainings and before and after inductions of a blocker of NMDA receptors, МK-801. The results prove that the glutamatergic transmitter system is significantly involved in the reaction of the respiratory system to presentation of a hypoxic stimulus within all stages of formation of the ventilatory response, both before and after the action of intermittent hypoxia. Blocking of NMDA receptors under conditions of adaptation to intermittent hypoxia exerted a more intense influence on the amplitude of respiratory EMG discharges of the diaphragm than on their frequency.
Keywordsintermittent hypoxia EMG activity diaphragm brainstem glutamate MK-801
- 2.G. E. Bisgard and J. A. Neubauer, “Peripheral and central effects of hypoxia,” in: Lung Biology in Health and Disease, Marcel Dekker, New York (1995), pp. 617-668.Google Scholar
- 5.H. Kazemi, C. H. Chiang, and B. Hoop, “Role of medullary glutamate in the hypoxic ventilatory response,” in: Comroe Memorial Symposium – Chemoreceptors and Reflex in Breathing, S. Lahiri (ed.), Oxford Univ. Press, New York (1989), pp. 233-242.Google Scholar
- 13.S. K. Coles, P. Ernsbergher, and T. E. Dick, “A role for NMDA receptors in posthypoxic frequency decline in the rat,” Am. J. Physiol. Regul. Integr. Comp. Physiol., 274, R1546-R1555 (1998).Google Scholar
- 14.A. Mizusawa, H. Ogawa, Y. Kikuchi, et al., “In vivo release of glutamate in nucleus tractus solitarii of the rat during hypoxia,” J. Physiol., 478.1, 55-65 (1994).Google Scholar