Figure 8.

A, B, Schematic drawing summarizing the interactions between implanted neural progenitor cells and the host (A) as well as the physiological response of abducens internuclear neurons (B). A, Scaffold of implanted cells (green) interacting with microglia (blue) and astrocytes (orange). Some sectioned axons in the MLF (yellow) established synaptic contacts with processes originating from implanted cells. D, Dorsal; C, caudal; R, rostral; V, ventral. B, The discharge characteristics and synaptic inputs of abducens internuclear neurons are illustrated. Control cells showed a balance of excitatory to inhibitory synaptic drives, which produced their typical tonic–phasic firing. Axotomy led to the loss of both excitatory and inhibitory boutons in similar proportions, resulting in a decrease in tonic and phasic signals. However, after the implant, axotomized abducens internuclear neurons completely recovered the tonic signals, whereas the re-establishment of the phasic signals was partial and paralleled a synaptic imbalance in favor of inhibition.