Functional and electrophysiological characterization of photochemical graded spinal cord injury in the rat.

This study characterizes by functional and electrophysiological methods changes following photochemically induced injuries to the spinal cord in adult rats. The spinal cord was exposed by laminectomy and bathed with 1.5% rose bengal solution for 10 min (T12-L1 vertebrae). The excess dye was removed by saline rinse and the spinal cord was irradiated with "cold" light for 0, 1, 2.5, 5, and 10 min in different groups of rats. During the first 15 days postlesion, locomotion activity, pain sensibility, motor and somatosensory evoked potentials, and motor and nerve action potentials were evaluated. Graded locomotor and nociceptive recovery was observed in irradiated rats depending on the photoinduction time. At 15 days, the amplitude of motor and sensory evoked potentials was significantly lower in irradiated groups with respect to control rats. The amplitude of compound muscle action potentials and of reflex H wave after sciatic nerve stimulation decreased significantly in irradiated animals with respect to control rats, while the latency did not show significant differences. In irradiated groups, significant differences were seen between pre- and postoperative values for most functional and electrophysiological parameters analyzed. A significant negative relationship was found between the area of cystic cavity of the spinal cord and the functional and electrophysiological impairment.