Temperature can alter the function outcome of spinal cord regeneration in larval lampreys

Now that spinal cord regeneration has been demonstrated in mammals [Bregman B. S. et al. (1995) Nature 378, 498-501; Cheng H. et al. (1996) Science 273, 510-513], we must examine the consequences and look for means of avoiding negative outcomes. The larval lamprey, which readily regenerates cut spinal axons, offers a model for this important next step. In the present study, one group of larval lampreys with spinal lesions was kept at room temperature during recovery. Another group was returned to their usual cold room temperature. A majority of animals kept at room temperature recovered full locomotor behavioral function, while a majority of those that recovered at a colder temperature exhibited dysfunctional locomotor behavior. The dysfunction most often consisted of segments rostral and caudal to the lesion site lacking the usual coordination and apparently interfering with each. In both groups, there was a close association between the presence of dysfunction and the quality of the intersegmental coordination as assessed in the isolated spinal cord preparation. These results suggest that a relatively minor difference in conditions under which an animal recovers may drastically alter the likelihood of a favorable functional outcome.