Differential expression of GDNF, BDNF, and NT-3 in the aging nigrostriatal system following a neurotoxic lesion.

Protein levels for brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and glial cell line-derived neurotrophic factor (GDNF) were measured in the striatum and ventral midbrain of young and aged Brown Norway/F344 F1 (F344BNF(1)) hybrid rats following a unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal pathway. At 2 weeks post-lesion, protein levels of BDNF and GDNF were higher in the denervated striatum when compared to the intact striatum for young (4-5 months old) but not old (31-33 months old) rats. Interestingly, in old rats BDNF protein in the denervated striatum was significantly lower than that measured in the intact striatum. At the same time point BDNF protein levels in the ventral midbrain were higher on the lesioned versus intact side for both young and old rats while no significant side differences were detected for GDNF protein in the ventral midbrain of young or old rats. No significant differences in NT-3 protein levels were detected between the lesioned and intact sides for striatal or ventral midbrain regions in either young or old brain. While no significant age effects were detected for BDNF or NT-3 protein, young rats showed higher GDNF protein levels in both the striatum (lesioned or intact) and ventral midbrain (lesioned or intact) than old rats. These data show that two endogenous neurotrophic factors, BDNF and GDNF, are differentially affected by a 6-OHDA lesion in the aging nigrostriatal system with young brain showing a significant compensatory increase of these two factors in the denervated striatum while no compensatory increase is observed in aged brain.

Co-grafts of fetal ventral mesencephalon and fibroblasts expressing sonic hedgehog: effect on survival and function of dopamine grafts.

Fibroblasts derived from the Rat2 parental cell line were genetically modified to express the cell-associated form of Sonic hedgehog (Shh) and then co-grafted along with E14 fetal ventral mesencephalon (VM) tissue into the denervated striatum of F344 rats; fetal VM grafts alone or co-grafts using the nonexpressing Rat2 fibroblasts served as controls. Seven weeks after grafting, co-grafts of fetal VM and fibroblasts expressing Shh (Rat2/Shh) contained significantly more tyrosine hydroxylase-positive (TH+) neurons than either the fetal VM grafts or co-grafts of fetal VM plus nonexpressing fibroblasts (Rat2). Despite a significantly higher yield of grafted TH+ neurons in the fetal VM + Rat2/Shh co-grafts than in either of the other two control groups, amphetamine-induced rotational behavior scores were not significantly different between any of the three treatment groups. The number of TH+ neurons in the Rat2 (nonexpressing) co-grafts was significantly lower than the other two treatment groups. The results from this study suggest that fibroblasts expressing Shh may improve the number of co-grafted dopamine neurons, but do not improve the functional capacity of the graft in terms of improving amphetamine-induced rotational behavior.

Dose-response curve and optimal dosing regimen of cyclosporin A after traumatic brain injury in rats.

Acute neuropathology following experimental traumatic brain injury results in the rapid necrosis of cortical tissue at the site of injury. This primary injury is exacerbated in the ensuing hours and days via the progression of secondary injury mechanism(s) leading to significant neurological dysfunction. Recent evidence from our laboratory demonstrates that the immunosuppressant cyclosporin A significantly ameliorates cortical damage following traumatic brain injury. The present study extends the previous findings utilizing a unilateral controlled cortical impact model of traumatic brain injury in order to establish a dose-response curve and optimal dosing regimen of cyclosporin A. Following injury to adult rats, cyclosporin A was administrated at various dosages and the therapy was initiated at different times post-injury. In addition to examining the effect of cyclosporin A on the acute disruption of the blood-brain barrier following controlled cortical impact, we also assessed the efficacy of cyclosporin A to reduce tissue damage utilizing the fluid percussion model of traumatic brain injury. The findings demonstrate that the neuroprotection afforded by cyclosporin A is dose-dependent and that a therapeutic window exists up to 24h post-injury. Furthermore, the optimal cyclosporin dosage and regimen markedly reduces disruption of the blood-brain barrier acutely following a cortical contusion injury, and similarly affords significant neuroprotection following fluid percussion injury. These findings clearly suggest that the mechanisms responsible for tissue necrosis following traumatic brain injury are amenable to pharmacological intervention.

Lesion-induced increase of BDNF is greater in the striatum of young versus old rat brain.

Young (4-5 month old) and old (32-34 month old) Brown Norway/F344 hybrid rats were given unilateral 6-OHDA lesions of the nigrostriatal pathway. Four weeks later tissue from the lesioned or intact striatum or ventral midbrain was dissected and analyzed for brain-derived neurotrophic factor (BDNF) protein levels using an enzyme-linked immunosorbent assay. BDNF protein content was greater in the lesioned striatum than in the intact striatum for all young rats, and the increased BDNF content in the lesioned striatum of young rats was directly correlated with severity of lesion as determined by rotational scores. BDNF content in the lesioned striatum increased in less than half of the old rats and was not significantly different than BDNF content in the intact striatum. BDNF content in the lesioned substantia nigra/ventral tegmental area (SN/VTA) was greater than BDNF content in the intact SN/VTA for both young and old rats. These data suggest that an age-related difference in activity of at least one neurotrophic factor, BDNF, occur within the denervated striatum following a neurotoxic lesion of the nigrostriatal pathway.

Basic fibroblast growth factor (bFGF) enhances tissue sparing and functional recovery following moderate spinal cord injury.

The rapid increase in basic fibroblast growth factor (bFGF) production following spinal cord injury (SCI) in rats is thought to serve a role in the cellular processes responsible for the functional recovery often observed. In this study, bFGF was intrathecally administered continuously for 1 week beginning 30 min after a moderate (12.5 mm) spinal cord contusion in adult rats using the New York University impactor device. Osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at a rate of 3 microg or 6 microg per day versus control vehicle. Animals were behaviorally tested for 6 weeks using the Basso, Beattie, Bresnahan locomotor rating scale and histologically assessed for both tissue sparing and glial reactivity rostral and caudal to the lesion. Rats treated with bFGF regained coordinated hindlimb movements earlier than controls and demonstrated consistent coordination from 4 to 6 weeks. Vehicle-treated rats showed only modest improvements in hindlimb function. The amount of spared tissue was significantly higher in bFGF-treated rats than in controls. Astrocyte and microglial reactivity was more pronounced in bFGF-treated animals versus controls. In summary, intrathecal infusion of exogenous bFGF following SCI significantly reduces tissue damage and enhances functional recovery. Early pharmacological intervention with bFGF following SCI may serve a neuroprotective role and/or create a proregenerative environment, possibly by modulating the neuroglial response.

GDNF partially protects grafted fetal dopaminergic neurons against 6-hydroxydopamine neurotoxicity.

Rats were given unilateral 6-hydroxydopamine (6-OHDA) lesions and subsequently received transplants of fetal ventral mesencephalic tissue into the denervated striatum. Four weeks later transplanted animals were tested for graft-mediated reduction of amphetamine-induced rotational behavior. Subsequently, transplanted animals received an intrastriatal injection of either GDNF (10 microg) or citrate buffer into a site lateral to the transplant, and then 6 h later received an injection of either 4.0 microg of 6-OHDA, 8.0 microg of 6-OHDA, or vehicle using the same stereotaxic coordinates that were used for the GDNF/citrate buffer injection. Animals were re-tested for amphetamine-induced rotational behavior 2 weeks later. Histological analysis revealed a significant reduction in the number of cell bodies immunostained for tyrosine hydroxylase (TH+) within the transplant for those animals pretreated with an intrastriatal injection of citrate buffer and subsequently given either dose of 6-OHDA. Transplanted animals pretreated with GDNF and subsequently administered 8.0 microg of 6-OHDA showed a significant reduction of TH+ neurons within the transplant compared to controls, however TH+ cell counts for this group remained significantly higher than the TH+ cell counts for the group of animals receiving the same dose of 6-OHDA but pretreated with citrate buffer. GDNF pretreatment completely protected TH+ cell bodies against 4.0 microg of 6-OHDA. Rotational scores indicated that GDNF provided only partial protection against 6-OHDA neurotoxicity in terms of transplant function. For both groups of transplanted animals receiving GDNF pretreatment and 6-OHDA injections, amphetamine-induced rotational scores dropped below the scores for animals pretreated with citrate buffer but remained significantly higher than the scores for transplanted animals that were not injected with 6-OHDA. Both histological and behavioral measures indicate GDNF partially protects integrated transplants against neurotoxic insult.