The c-fos gene expression method was used to localize brainstem neurons functionally related to the tracheal-bronchial cough on 13 spontaneously breathing, pentobarbitone anesthetized cats. The level of Fos-like immunoreactivity (FLI) in 6 animals with repetitive coughs (170+/-12) induced by mechanical stimulation of the tracheobronchial mucosa was compared to FLI in 7 control non-stimulated cats. Thirty-four nuclei were compared for the number of labeled cells. Enhanced cough FLI was found bilaterally at following brainstem structures, as compared to controls: In the medulla, FLI was increased in the medial, interstitial and ventrolateral subnuclei of the solitary tract (p < 0.02), in the retroambigual nucleus of the caudal medulla (p < 0.05), in the ambigual, paraambigual and retrofacial nuclei of the rostral medulla along with the lateral reticular nuclei, the ventrolateral reticular tegmental field (p < 0.05), and the raphe nuclei (p < 0.05). In pons, increased FLI was detected in the lateral parabrachial and Kölliker-Fuse nuclei (p < 0.01), in the posteroventral cochlear nuclei (p < 0.01), and the raphe midline (p < 0.05). Within the mesencephalon cough-related FLI was enhanced at the rostral midline area (p < 0.05), but a decrease was found at its caudal part in the periaqueductal gray (p < 0.02). Results of this study suggest a large medullary - pontine - mesencephalic neuronal circuit involved in the control of the tracheal-bronchial cough in cats.

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Despite high behavioural similarity, some differences in the central neural control of the cough and sneeze reflexes have been suggested. The main aim of our study was to analyze and compare characteristics of electromyographic (EMG) activities of the respiratory muscles during these two behaviours.Data were taken from eight adult rabbits under pentobarbital anaesthesia. We compared diaphragm EMG activities in tracheobronchial cough, sneeze, and quiet breathing during inspiration. Electromyograms were read from the abdominal muscles during the expiratory phases of coughing and sneezing. Due to the non-stationary character of electromyographic signals, we used wavelet analysis to determine the time-frequency distribution of energy during the behaviours.Inspiratory durations of all above mentioned behaviours were similar. The maximum inspiratory power occurred later in sneeze than during quiet inspiration (P < 0.05). The total inspiratory power during sneeze was higher compared to that in cough (P < 0.05) and quiet inspiration (P < 0.01). Lower frequencies contributed to this increase significantly more in sneeze compared to cough (less than 287.5 Hz, P < 0.05; 287.5 Hz up to 575 Hz, P < 0.01). We found similar energy distribution for coughing and quiet inspiration. Its maximum occurred at lower frequency in quiet inspiration compared to sneezing (P < 0.01). The abdominal burst during cough was longer than that in sneezing (P < 0.001).Our results support the concept that both cough and eupnoeic inspiration are generated by similar neuronal structures. A non-specific mechanism producing expiratory activity during tracheobronchial cough and sneeze is suggested.

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