ISSN:
1432-2013
Keywords:
Bulbar respiratory centre
;
Inspiratory neurons
;
Respiratory movements
;
Neuronal classification
;
Metabolic modifiers of neuronal activity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary 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 distension or collapse (α- or β-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 I α + units were activated by 5 mM glucose-6-phosphate (G-6-P) and 3.5 mM 3-phosphoglycerate (3-PGA), which both inhibited I β + neurons, while 5 mM AMP inhibited I α + much more strongly than I β + cells. The spike density of I α − and I β − 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 I α − but inhibited the I β − neurons. The EIβ units were characteristically activated by 10 mM citrate, which inhibited all I-type neurons. Activations of the Iα and Iβ neurons led to an accelerated respiratory rate and a higher tidal volume, while the opposite was true for EIβ neurons. Intravenous injection of metabolites could not duplicate the striking effects under local applications.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00583627
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