ISSN:
1432-1106
Keywords:
Pons
;
Respiratory neurons
;
Trigeminal system
;
Reticular formation
;
Respiratory oscillators
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The upper and middle pons and the lower mesencephalon of the cat were explored with extracellular microelectrodes in a search for respiratory related units (RRU). The preparation used, the unanesthetized normocapnic cat, resulted in an “isolated respiratory center” by eliminating input from, as well as output to, lung and thorax. Observations were done in standard experimental conditions which allowed quantitative comparisons of anatomical structures with respect to RRU density (RRUD), RRUD to total unit density (UD) ratio, and a respiratory modulation index (RMI). Units were recorded in 22 anatomical structures; of 3614 units kept for analysis, 46.9% had a definite respiratory rhythm. The phase relations of frequency variation ere classified into five main categories: 1) tonic expiratory (E) or 2) inspiratory (I) patterns, 3) phase spanning inspiratory-expiratory (IE) or 4) expiratoryinspiratory (EI) patterns, and 5) tonic early expiratory depressed (EED) pattern. Densely packed RRU were recorded in anatomical structures known to be involved in the command of respiratory accessory musculature (trigeminal system) or thought to be part of the pneumotaxic machinery (nucleus parabrachialis median's, Kölliker-Fuse nucleus). In these structures, RRU proportion was 57–89% of the total neuronal activity. On the other hand, definite RRU (10–26%) were recorded in structures which are not thought to have a respiratory function (such as inferior colliculus or griseum centralis) where isolate RRU were scattered among non-respiratory tonic units. This group includes nuclei sometimes considered as having a pneumotaxic function. The pontine reticular formation represents an intermediate category (RRU = 35.6%) where clusters of RRU alternate with non-respiratory modulated cells. The possible role of these clusters is discussed in relation to the hypothesis of multiple coupled respiratory oscillators. Variance analysis of RRUD, RRUD to UD ratio and RMI shows highly significant differences between the three preceding categories of structures.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00233430
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