A small dose of the immunosuppressive agent FK506 (tacrolimus) protects peripheral nerve from ischemic fiber degeneration

The immunosuppressant agent FK506 (tacrolimus) has proven to be neuroprotec tive against brain ischemia, but there are no data on potential neuroprotec tive effects of FK506 in peripheral nerve ischemia. We examined the potenti al effects of two doses of FK506 in protecting peripheral nerve from ischem ic fiber degeneration. Ischemia in the left sciatic nerve of the rat was pr oduced by injecting 2 x 10(6) microspheres (14 mum) into the left femoral, hypogastric, and superior gluteal arteries in proportions of 47%, 37%, and 17%, respectively. After embolization, FK506 was injected into the left fem oral, hypogastric, and superior gluteal arteries in doses of 9.4, 7.4, and 3.4 mug, respectively, for the high-dose group and 4.7, 3.7, and 1.7 mug, r espectively, for the low-dose group. The control rats were injected with sa line. FK506 treatment resulted in dramatic behavioral improvement in nerve function, in the number of functioning nerve fibers, and in the salvage of a majority of nerve fibers from ischemic fiber degeneration in a dose-depen dent fashion. These results suggest that a small dose of FK506 protects per ipheral nerve from ischemic fiber degeneration and that it may have potenti al in the treatment of ischemic neuropathy. (C) 2001 John Wiley & Sons, Inc .