[The development of periodic apneic breathing during the activation of the GABA-ergic system of the brain].

Experiments on sodium pentobarbital (40 mg/kg i.p.) anesthetized mongrel cats of either sex weighing from 2.25 to 4.25 kg showed that administration of sodium hydroxybutyrate (200 mg/kg, i.v.) resulted in periodic apneic breathing with inspiratory arrests in more than 80%. An abrupt decrease of respiratory rate and thus ventilation was conditioned by a prolonged activation of inspiratory muscles (diaphragm and external intercostals). Under these conditions, the activity of expiratory muscles (internal intercostals and abdominal muscles) was not depressed. The changes in the respiratory pattern were not due to alterations in systemic hemodynamics. The periodic breathing affected the arterial blood components as follows: the most pronounced variations were in pO2 less pronounced ones in pCO2 and the smallest ones in pH. After the periodic apneic breathing formation, vagotomy either produced no marked alterations in the respiratory pattern or even promoted restoration of more regular breathing. It is assumed that the activation of GABA-ergic system of the brain can interfere with the generation of the respiratory rhythm depressing the "switch-off" mechanism and breaking the vagal afferent transmission to the neurons of respiratory centre.