Cough and swallow after laparotomy in anesthetized cats.

An anesthetized cat animal model was used to evaluate changes in cough and swallow after a small midline upper abdominal incision (laparotomy). Two additional conditions were tested: sealing the laparotomy with gentle suctioning via a small cannula, and subsequent closure of the abdominal wall with suture. These abdominal wall manipulations resulted in no changes in the cough reflex, but produced higher motor drive to pharyngeal musculature (thyropharyngeus and geniohyoid muscles) during swallow. Swallow-breathing coordination phase preference shifted towards swallow occurring more during the inspiratory phase. There were no significant changes in cough motor pattern, or cough and swallow number and temporal features. The respiratory changes were limited to reduced inspiratory motor drive to the diaphragm. The results are consistent with an important role of sensory feedback from the abdominal wall in regulation of swallow motor pattern. The level of reflex modulation may depend on the extent of injury and likely on its position in the abdomen.

Differential inhibition of cough by GABAA and GABAB receptor antagonists in the nucleus of the solitary tract in cats.

Bicuculline and saclofen were microinjected into the rostral (rNTS) and caudal nucleus of the solitary tract (cNTS) in 17 anesthetized cats. Electromyograms (EMGs) of the diaphragm (DIA) and abdominal muscles (ABD), esophageal pressures (EP), and blood pressure were recorded and analyzed. Bilateral microinjections of 1 mM bicuculline in the rNTS significantly reduced the number of coughs (CN), amplitudes of DIA and ABD EMG, inspiratory and expiratory EP, and prolonged the duration of the cough expiratory phase (CTE) as well as the total cough cycle duration (CTtot). Bilateral microinjections of 2 mM saclofen reduced only cough expiratory efforts. Bilateral microinjection of bicuculline in the cNTS significantly reduced CN and amplitudes of ABD EMG and elongated CTE and CTtot. Bilateral microinjections of saclofen in cNTS had no significant effect on analyzed cough parameters. Our results confirm a different GABAergic inhibitory system in the rNTS and cNTS acting on mechanically induced cough in cats.

Volume feedback during cough in anesthetized cats, effects of occlusions and modulation summary.

The study investigates the effects of 6 occlusion conditions on the mechanically induced cough reflex in 15 anesthetized (pentobarbital) spontaneously breathing cats (14♂, 1♀). Esophageal pressure and integrated EMG activities of inspiratory (I) diaphragm and expiratory (E) abdominal muscles were recorded and analyzed. Occlusions: inspiratory (Io), continual I (cIo), during I and active E (I+Eo) cough phase, during I and then E phase with short releasing of airflow before each phase (I-Eo), and E occlusion (Eo) had little influence on cough number. Only continual E occlusion (cEo) reduced the number of coughs by 19 % (to 81 %, p < 0.05). Cough I esophageal pressure reached higher amplitudes under all conditions, but only Eo caused increased I diaphragm motor drive (p < 0.05). Cough E efforts (abdominal motor drive and E amplitudes of esophageal pressure) increased during Eo, decreased during I+Eo (p < 0.05), and did not change significantly under other conditions (p > 0.05). All I blocks resulted in prolonged I cough characteristics (p < 0.05) mainly cough I phase (incrementing part of the diaphragm activity). Shorter I phase occurred with cEo (p < 0.05). Cough cycle time and active E phase (from the I maximum to the end of cough E motor drive) prolonged (p < 0.05) during all occlusions (E phase duration statistically non-significantly for I+Eo). Airflow block during cough (occlusions) results in secondary changes in the cough response due to markedly altered function of cough central pattern generator and cough motor pattern produced. Cough compensatory effects during airflow resistances are more favorable compared to occlusions. Volume feedback represents significant factor of cough modulation under various pathological obstruction and/or restriction conditions of the respiratory system.