Spontaneous respiratory rhythm generation in in vitro upper cervical slice preparations of neonatal mice

Isolated upper cervical slice preparations were prepared from neonatal mice to examine whether spontaneous respiratory activity could be generated in the preparations. By using brainstem-spinal cord preparations, we first recorded from the cervical C1-C2 and C4 ventral roots rhythmic bursts which were synchronized with respiratory burst activity of the hypoglossal (XIIth) nerve. Following transection just above the C1 segment, smaller and slower rhythmic bursts still persisted in the C1/C2 ventral roots and these were synchronized with those in the C4 ventral root. The present result, that a bursting rhythm remained in the C1/C2 slices, suggests that the spinal neuronal circuit for generating respiratory rhythm is localized in the upper cervical segments which contain upper cervical inspiratory neurons.