title: Metabolic control of respiratory neuronal activity and the accompanying changes in breathing movements of the rabbit. 1. Mainpulation of inspiratory and expiratory-inspiratory neurons.
abstract: The property of the neuronal membrane to be permeable to metabolic modifiers of two regulatory enzymes has been utilized to manipulate the spike activity of inspiratory (I) and expiratory-inspiratory (EI) neurons of the bulbar respiratory centre. The neurons have been classified according to their response to lung distention or collapse (alpha- or beta-type) and to hyperventilation (tonic firing denoted by "+", cessation of activity by "-"). Using extracellular microelectrodes for single unit recording, the medulla oblongata was superfused with a metabolite-containing CSF. The various neuronal sub-types exhibited a differential activating or inhibitory response to one or several metabolic effectors. For example Ialpha+ units were activated by 5 mM glucose-6-phosphatase (G-6-P) and 3.5 mM 3-phosphoglycerate (3-PGA), which both inhibited Ibeta+ neurons, while 5 mM AMP inhibited Ialpha+ much more strongly than Ibeta+ cells. The spike density of Ialpha- and Ibeta- neurons was increased in the presence of 2.5 mM fructose-6-phosphate and 3.5--5 mM AMP, but became reduced by G-6-P. In contrast, 3 mM fructose-1,6-diphosphate and 5 mM 3-PGA activated the Ialpha- but inhibited the Ibeta- neurons. The EIbeta units were characteristically activated by 10 mM citrate, which inhibited all I-type neurons. Activations of the Ialpha and Ibeta neurons led to an accelerated respiratory rate and a higher tidal volume, while the opposite was true for EIbeta neurons. Intravenous injection of metabolites could not duplicate the striking effects under local applications.
mesh_terms: D000818:Animals; D001683:Biological Clocks; D004594:Electrophysiology; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D006985:Hyperventilation; D009474:Neurons / Q000201:enzymology / Q000502:physiology*; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D011817:Rabbits; D012119:Respiration; D012125:Respiratory Center / Q000201:enzymology / Q000502:physiology*; D013990:Tidal Volume
chemical_list: D010732:Phosphofructokinase-1; D006597:Fructose-Bisphosphatase