Fig. 1.

Schematic illustrations of recordings of respiratory activity in the upper cervical slice preparations. Spontaneous bursts were recorded from the hypoglossal (XIIth) nerves and the ventral roots of C1–C4 in the brainstem spinal-cord preparations by using suction electrodes. Rhythmic C1 bursting activity was established as respiratory in nature by synchronized XIIth nerve activity (upper right). Significant differences between the bursts frequencies of the XIIth nerve and the C1 roots were not observed (n = 8, paired t tests; lower right). Horizontal lines A and B on the diagram of the brainstem spinal-cord preparation indicate the transection levels which were used to make the upper cervical slice preparations. The putative upper cervical inspiratory neurons (UCINs) and the phrenic motoneurons (Phrenic MNs) are located in the C1–C2 and the C3–C5 levels, respectively