PERIPHERAL, BUT NOT CENTRAL, NERVOUS-SYSTEM ABNORMALITIES ARE REVERSED BY PANCREATIC-ISLET TRANSPLANTATION IN DIABETIC LEWIS RATS

Neuroelectrophysiological recordings represent a non-invasive and repr oducible method of detecting central and peripheral nervous system alt erations in diabetes mellitus. In order to evaluate whether the normal ization of metabolic control obtained by pancreatic islet transplantat ion could reverse diabetic neuroelectrophysiological alterations, or p revent further deterioration, we used an experimental model in which p ancreatic islets (n = 1200) were injected into the portal vein of inbr ed Lewis rats (used as islet donors as well as recipients). Islets wer e injected 4 months after diabetes induction, since previous work had shown functional but not morphological damage at the nervous tissue le vel at this stage of the disease. Visual (V), brainstem auditory (BA) and somatosensory (S) evoked potentials (EPs) were measured in strepto zotocin-induced, islet-recipient diabetic rats (n = 7), streptozotocin -induced diabetic rats (n = 16) and non-diabetic control rats (n = 12) . Metabolic parameters and electrophysiological recordings were evalua ted before diabetes induction, before transplantation and 4 months lat er. After transplantation, glycaemic levels returned to normal values within 1 week and remained so until the end of the study, as confirmed by a normal oral glucose tolerance test and by an increase in body we ight. Electrophysiological recordings were altered in diabetic animals before transplantation. Four months after transplantation EP recordin gs improved, with a detectable gradient from the peripheral to the cen tral structures. SEPs were significantly improved in the peripheral ta rsus-L6 tract and the L6-cortex tract (P < 0.005 and P < 0.01 versus d iabetic rats) and were ameliorated without achieving statistical signi ficance in the central T6-cortex tract. BAEP latency values tended to improve in transplanted rats, but the differences versus non-transplan ted diabetic animals failed to reach significance. VEP values remained clearly pathological and even deteriorated after transplantation. The se results show that normalization of metabolic control by pancreatic islet transplantation can reverse some of the already established neur oelectrophysiological alterations at the peripheral nervous system lev el, but does not affect other alterations at the central nervous syste m level.