Müller cells and other reticulospinal neurones are phasically active during fictive locomotion in the isolated nervous system of the lamprey.

Reticulospinal neurones were studied during fictive locomotion in the lamprey brainstem-spinal cord in vitro preparation. Intracellular recordings were made from the large reticulospinal Müller cells located in the mesencephalon (M1-3), rostral (I1) and middle (B1-5) rhombencephalon, the Mauthner cells, and the V cells located within the posterior reticular nucleus during fictive locomotor activity. All cells were depolarized during motor activity on either the ipsilateral (M1-3, I1, B1-5 and V cells) or the contralateral (Mauthner cell (crossed axon] side. During locomotor activity and long-lasting burst activity, phasic membrane potential oscillations occurred well correlated to the ventral root activity.