6533b820fe1ef96bd127a30c

RESEARCH PRODUCT

Metabolic control of respiratory neuronal activity and the accompanying changes in breathing movements of the rabbit

subject

description

Expiratory-related neurons have been classified according to their phase relation within the respiratory cycle, their response to lung distension and collapse (α- and β-type), and to hyperventilation (tonic firing denoted by “+”, cessation of activity by “−”). The dorsal surface of the medulla oblongata was superfused with a metabolite-containing CSF solution and the activity of expiratory (E) and inspiratory-expiratory (IE) neurons was extracellularly recorded. The neuronal sub-types established by their functional behaviour could equally be distinguished by their differential response to one or several metabolites. In contrast to inspiratory (I) neurons, E − α , E + β , E − β and IE − β neurons are inhibited by 3.5 mM AMP, but are activated by 10 mM citrate (with the exception of E + β units). Furthermore I cells are activated by ATP, while Eα and Eβ units become inhibited. Vagotomy in some instances affected the response of some IEβ units. An increase in spike density of IE + β and E − α cells in paralleled by a reduction of both the respiratory rate and the tidal volume, while a lower spike density in IE + β , IE − β and E − α units is accompanied by increases in respiratory rate and tidal volume. In the case of E + β and E − β cells lower activity is associated with an increased tidal volume. No metabolite-induced changes could be obtained with cardiovascular or unspecific reticular neurons.