Effect of lateral cervical cord lesions on the respiratory rhythm of anaesthetized, decerebrate cats after vagotomy

Abstract

SUMMARY1. The lateral cervical cord of vagotomized, anaesthetized cats was superficially lesioned at the C3 or the C7 level before or after midcollicular decerebration.2. These cord lesions eliminated the inhibition of diaphragmatic discharge caused by chest compression. Previous work (Remmers, 1973) indicates that this change can be attributed to loss of reflex inhibition of inspiratory activity by intercostal afferents, probably as a result of interruption of tracts ascending in the lateral columns.3. Decerebrate cats with bilateral cervical cord lesions displayed abnormal respiratory patterns, ranging from apnoea to apneusis.4. The results are consistent with the hypothesis that the lateral columns carry proprioceptive feed-back from intercostal mechanoreceptors which promotes rhythmic breathing in the anaesthetized decerebrate cat.

Extra‐segmental reflexes derived from intercostal afferents: phrenic and laryngeal responses

“…The 1 mm deep cut, above or below the level of the phrenic outflow, had little influence on the spontaneous phrenic or recurrent laryngeal discharges in most cases. Similar observations were made by Remmers & Tsiaras (1973), who, in addition, found no significant change in end-tidal Pco2. Occasionally, a lesion at the C3 level, ipsilateral to the site of phrenic recording, diminished spontaneous phrenic discharge, and in one case all rhythmic discharge ceased.…”

“…Effects I I in 1 a -AAid INTERCOSTAL REFLEXES 5 the sections were similar to those reported elsewhere (Remmers & Tsiaras, 1973). The 1 mm deep cut, above or below the level of the phrenic outflow, had little influence on the spontaneous phrenic or recurrent laryngeal discharges in most cases.…”

“…If the extra-segmental reflexes derived from the mid-thoracic region are mediated by bulbopontine respiratory mechanisms, they may, by inhibiting inspiration and facilitating expiration, participate in setting the respiratory pattern in some situations. This possibility is discussed in another paper (Remmers & Tsiaras, 1973).…”

Diaphragm electromyographic activity following unilateral midcervical contusion injury in rats

“…White-matter sparing. In contusion animals, substantial white-matter damage was observed around the lesion epicenter, which would disrupt both descending ipsilateral-bulbospinal innervation (ventromedial and lateral columns) (Lipski et al 1994) and ascending propriospinal inputs (lateral columns) (Decima and von Euler 1969;Dimarco and Kowalski 2013;Remmers and Tsiaras 1973) to the phrenic nucleus. Of note, other studies, including those using higher contusion-injury forces, report similar patterns of white-matter injury encompassing the dorsal, lateral, and ventral funiculi (Awad et al 2013;Choi et al 2005;Lane et al 2012).…”

Mechanics of the Chest Wall during Restrictive Thoracic Strapping

“…[11] have recently shown the occurrence of muscle spindles and tonic activity in the human diaphragm, and such reflexes could operate in conditions involving a downward displacement of the diaphragm. Furthermore, several investigators have reported that chest compression in animals provoked alterations in phrenic efferent activity via intercostal-to-phrenic reflexes from both the middle and lower thoracic region [3,14]. The nar row scatter of the data points suggests, however, that the 4 subjects tested were able to adequately relax their respiratory muscles to obtain reliable PV curves of the chest wall in the strapped state as well (see below).…”