Fig. 1. Schematic diagram of the lamprey isolated spinal cord preparation and anesthetic delivery system. The isolated cord (45–50 segments) was excised and placed into a bath, which was then separated using notched acrylic dividers that were sealed around the spinal cord and walls of the bath with petroleum jelly. The rostral and caudal thirds of the spinal cord were superfused separately from the middle third. A conduit linked the flows to the rostral and caudal compartments of the bath. The perfusion system for the middle compartment had an isoflurane (ISO) vaporizer in line with the gas flow to permit delivery of isoflurane to the middle compartment only ( shaded region ), while one ventral root (VR) was recorded in each compartment.