Experimental hyperthyroidism increases the effectiveness of predegenerated peripheral nerve graft implantation into hippocampus of adult rats.

Purpose: The aim of the study was to ascertain whether experimental hyperthyroidism changes the neurotrophic activity of 14- and 21-day-predegenerated peripheral nerve grafts towards CNS neurites.

Methods: Hyperthyroidism was induced by subcutaneous injections of T_4. Autologous peripheral nerve grafts were implanted into the hippocampus of both euthyrotic and hyperthyrotic animals 14 or 21 days after sciatic nerve transection (groups ET14, Et21, Ht14 and Ht21, respectively). Non-predegenerated grafts were used as a control group (groups EtN adn HtN). Cells extending their neurites into the grafts were traced with FITC-HRP.

Results: The number of traced cells in individual groups was as follows: EtN - 39.4 +/- 9.46, Et14 - 1 +/- 0.94, Et21 - 0.6 +/- 0.69; HtN - 95 +/- 19.46; Ht14 - 95.94 +/- 16.3, Ht21 - 99.94 +/- 7.26.

Conclusions: We found that experimentally induced hyperthyroidism strongly enhanced the regeneration of injured hippocampal neurites after implantation of peripheral nerve grafts that were practically inactive in euthyrotic animals.