Respiratory interneurons of the lower cervical (C4-C5) cord: membrane potential changes during fictive coughing, vomiting, and swallowing in the decerebrate cat

Abstract

The possible roles of interneurons in the C4-C5 cervical spinal cord in conveying central drives to phrenic motoneurons during different behaviour patterns were investigated using intracellular recordings in decerebrate, paralysed, artificially ventilated cats. Eleven cells were tentatively classified as respiratory interneurons since they: (i) could not be antidromically activated from the ipsilateral whole intrathoracic phrenic nerve, and (ii) exhibited large membrane potential changes during eupnea (7.3 mV +/- 3.6, range 2-13.5 mV) or non-respiratory behaviour patterns. Six neurons depolarized in phase with phrenic discharge; four others depolarized during the expiratory phase; one neuron exhibited depolarization during the end of both expiration and inspiration. A variety of responses was observed during fictive coughing, vomiting, and swallowing. The results are consistent with C4-C5 expiratory interneurons conveying inhibition to phrenic motoneurons during different behaviour patterns. The responses of inspiratory and multiphasic neurons suggest that the roles of these interneurons are mode complex than simply relaying central excitatory or inhibitory drive to phrenic motoneurons.

Activity of descending propriospinal axons in the turtle hindlimb enlargement during two forms of fictive scratching: phase analyses

“…activity has been recorded from individual spinal premotor interneurons during both fictive swimming and fictive struggling in embryonic tadpoles (Soffe et al, 1984;Soffe, 1993). Individual cervical propriospinal neurons in the cat have been shown to be rhythmically active during fictive respiration, in addition to fictive vomiting, fictive coughing, or fictive swallowing (Nonaka and Miller, 199 1;Grelot et al, 1993). Rhythmic activity has also been recorded from Ia inhibitory interneurons, ventral spinocerebellar tract neurons, and Renshaw cells in the cat spinal cord during actual or fictive scratching (Arshavsky et al, 1978;Deliagina and Orlovsky, 1980;Deliagina and Feldman, I98 1) and actual or fictive locomotion (Arshavsky et al, 1972;Feldman and Orlovsky, 1975;Pratt and Jordan, 1987) although scratching and locomotion were elicited during different recordings.…”

Physiology and Morphology of Shared and Specialized Spinal Interneurons for Locomotion and Scratching

“…There is also evidence for sharing of some spinal interneuronal circuitry between walking and paw-shaking in cats (Carter and Smith 1986), walking and hatching in chicks (Bekoff et al 1987(Bekoff et al , 1989, swimming and struggling in tadpoles (Green and Soffe 1996;Li et al 2007;Soffe 1993Soffe , 1996, swimming and escape movements in fish (Kimura et al 2006;Ritter et al 2001;Svoboda and Fetcho 1996), limb withdrawal and scratching in turtles (Berkowitz et al 2006;Currie and Stein 1989), and the three forms of scratching in turtles (Berkowitz 2001b(Berkowitz , 2005Berkowitz and Stein 1994;Mortin and Stein 1989;Robertson et al 1985;Stein et al 1986). Evidence also suggests there is some shared central circuitry for vertebrate respiratory behaviors such as eupneic breathing, sighing, gasping, coughing, and sneezing, as well as swallowing and vomiting (Gestreau et al 1996;Grelot et al 1993;Lieske et al 2000;Oku et al 1994;Shiba et al 2007;Yajima and Larson 1993).…”

Omnidirectional walking using central pattern generator

“…Control of locomotion in the decerebrate cat shows that locomotion signals are locally produced in spinal cord and by separate mechanism, without higher brain interference [7]. This evidence shows that animals' locomotion signals are generated in spinal cord by circuit called central pattern generator (CPG) [8].…”