Age and lesion-induced increases of GDNF transgene expression in brain following intracerebral injections of DNA nanoparticles.

In previous studies that used compacted DNA nanoparticles (DNP) to transfect cells in the brain, we observed higher transgene expression in the denervated striatum when compared to transgene expression in the intact striatum. We also observed that long-term transgene expression occurred in astrocytes as well as neurons. Based on these findings, we hypothesized that the higher transgene expression observed in the denervated striatum may be a function of increased gliosis. Several aging studies have also reported an increase of gliosis as a function of normal aging. In this study we used DNPs that encoded for human glial cell line-derived neurotrophic factor (hGDNF) and either a non-specific human polyubiquitin C (UbC) or an astrocyte-specific human glial fibrillary acidic protein (GFAP) promoter. The DNPs were injected intracerebrally into the denervated or intact striatum of young, middle-aged or aged rats, and glial cell line-derived neurotrophic factor (GDNF) transgene expression was subsequently quantified in brain tissue samples. The results of our studies confirmed our earlier finding that transgene expression was higher in the denervated striatum when compared to intact striatum for DNPs incorporating either promoter. In addition, we observed significantly higher transgene expression in the denervated striatum of old rats when compared to young rats following injections of both types of DNPs. Stereological analysis of GFAP+ cells in the striatum confirmed an increase of GFAP+ cells in the denervated striatum when compared to the intact striatum and also an age-related increase; importantly, increases in GFAP+ cells closely matched the increases in GDNF transgene levels. Thus neurodegeneration and aging may lay a foundation that is actually beneficial for this particular type of gene therapy while other gene therapy techniques that target neurons are actually targeting cells that are decreasing as the disease progresses.

Development and pharmacological characterization of a model of sleep disruption-induced hypersensitivity in the rat.

BACKGROUND: Sleep disturbance is a commonly reported co-morbidity in chronic pain patients, and conversely, disruption of sleep can cause acute and long-lasting hypersensitivity to painful stimuli. The underlying mechanisms of sleep disruption-induced pain hypersensitivity are poorly understood. Confounding factors of previous studies have been the sleep disruption protocols, such as the 'pedestal over water' or 'inverted flower pot' methods, that can cause large stress responses and therefore may significantly affect pain outcome measures. METHODS: Sleep disruption was induced by placing rats for 8 h in a slowly rotating cylindrical cage causing arousal via the righting reflex. Mechanical (Von Frey filaments) and thermal (Hargreaves) nociceptive thresholds were assessed, and plasma corticosterone levels were measured (mass spectroscopy). Sleep disruption-induced hypersensitivity was pharmacologically characterized with drugs relevant for pain treatment, including gabapentin (30 mg/kg and 50 mg/kg), Ica-6p (Kv7.2/7.3 potassium channel opener; 10 mg/kg), ibuprofen (30 mg/kg and 100 mg/kg) and amitriptyline (10 mg/kg). RESULTS: Eight hours of sleep disruption caused robust mechanical and heat hypersensitivity in the absence of a measurable change in plasma corticosterone levels. Gabapentin had no effect on reduced nociceptive thresholds. Ibuprofen attenuated mechanical thresholds, while Ica-6p and amitriptyline attenuated only reduced thermal nociceptive thresholds. CONCLUSIONS: These results show that acute and low-stress sleep disruption causes mechanical and heat hypersensitivity in rats. Mechanical and heat hypersensitivity exhibited differential sensitivity to pharmacological agents, thus suggesting dissociable mechanisms for those two modalities. Ultimately, this model could help identify underlying mechanisms linking sleep disruption and hypersensitivity.

Long distance directional growth of dopaminergic axons along pathways of netrin-1 and GDNF.

Different experimental and clinical strategies have been used to promote survival of transplanted embryonic ventral mesencephalic (VM) neurons. However, few studies have focused on the long-distance growth of dopaminergic axons from VM transplants. The aim of this study is to identify some of the growth and guidance factors that support directed long-distance growth of dopaminergic axons from VM transplants. Lentivirus encoding either glial cell line-derived neurotrophic factor (GDNF) or netrin-1, or a combination of lenti-GDNF with either lenti-GDNF family receptor α1 (GFRα-1) or lenti-netrin-1 was injected to form a gradient along the corpus callosum. Two weeks later, a piece of embryonic day 14 VM tissue was transplanted into the corpus callosum adjacent to the low end of the gradient. Results showed that tyrosine hydroxylase (TH(+)) axons grew a very short distance from the VM transplants in control groups, with few axons reaching the midline. In GDNF or netrin-1 expressing groups, more TH(+) axons grew out of transplants and reached the midline. Pathways co-expressing GDNF with either GFRα-1 or netrin-1 showed significantly increased axonal outgrowth. Interestingly, only the GDNF/netrin-1 combination resulted in the majority of axons reaching the distal target (80%), whereas along the GDNF/GFRα-1 pathway only 20% of the axons leaving the transplant reached the distal target. This technique of long-distance axon guidance may prove to be a useful strategy in reconstructing damaged neuronal circuits, such as the nigrostriatal pathway in Parkinson's disease.

Transgene expression in the striatum following intracerebral injections of DNA nanoparticles encoding for human glial cell line-derived neurotrophic factor.

A goal of our studies is to develop a potential therapeutic for Parkinson's disease (PD) by a human glial cell line-derived neurotrophic factor (hGDNF) expression plasmid administered to the rat striatum as a compacted DNA nanoparticle (DNP) and which will generate long-term hGDNF expression at biologically active levels. In the present study, we used a DNA plasmid encoding for hGDNF and a polyubiquitin C (UbC) promoter that was previously shown to have activity in both neurons and glia, but primarily in glia. A two-fold improvement was observed at the highest plasmid dose when using hGDNF DNA incorporating sequences found in RNA splice variant 1 compared with splice variant 2; of note, the splice variant 2 sequence is used in most preclinical studies. This optimized expression cassette design includes flanking scaffold matrix attachment elements (S/MARs) as well as a CpG-depleted prokaryotic domain and, where possible, eukaryotic elements. Stable long-term GDNF activity at levels 300-400% higher than baseline was observed following a single intracerebral injection. In a previous study, DNP plasmids encoding for reporter genes had been successful in generating long-term reporter transgene activity in the striatum (>365 days) and in this study produced sustained GDNF activity at the longest assessed time point (6 months).

Effects of binge ethanol administration on the behavioral outcome of rats after lateral fluid percussion brain injury.

This study examined the effects of 4 weeks of binge ethanol administration (BEAn) on the behavioral outcome in rats after lateral fluid percussion (FP) brain injury. Rats were intragastrically given 7.5 mL/kg of either 40% ethanol in 5% glucose solution (3 g ethanol/kg; binge ethanol group), or 5% glucose solution (vehicle group), twice on Thursday and Friday of 3 consecutive weeks. Then rats from both groups were subjected to either lateral FP brain injury of moderate severity (1.8 atm) or to sham operation. Postinjury behavioral measurements revealed that brain injury caused significant spatial learning disability in both groups. There were no significant differences in mean search latencies in the sham animals between the vehicle and binge ethanol groups. On the other hand, the mean search latency of the binge ethanol group was significantly higher than that of the vehicle group in trial blocks 2 and 4. There were no significant differences in the target visits (expressed as mean zone difference [MZD]) during the probe trial between the injured animals of binge ethanol and vehicle groups. However, there was only a minor trend towards worsened MZD score in the binge-injured animals. Histologic analysis of injured animals from both injured ethanol and vehicle groups revealed similar extents of ipsilateral cortical and observable hippocampal damage. These results suggest that 4 weeks of binge ethanol treatment followed by ethanol intoxication at the time of injury worsens some aspects of the spatial learning ability of rats. This worsening is probably caused by subtle, undetectable morphologic damage by binge ethanol administration.

Regional expression of Par-4 mRNA and protein after fluid percussion brain injury in the rat.

Regional levels of prostate apoptosis response-4 (Par-4) protein and mRNA were measured after lateral fluid percussion (FP) brain injury in rats. Immunochemical studies indicated that Par-4 immunoreactivity (ir) is present in cortical neurons and hippocampal CA1-CA3 pyramidal neurons in uninjured rats. Increases of Par-4-ir were observed in the CA3 neurons of the ipsilateral hippocampus (IH), but not in injured left cortex (IC) at 48 h after FP brain injury. Levels of the Par-4 mRNA measured by RT-PCR assay and protein measured by Western blot procedure were significantly increased in the injured IC and IH, but not in the contralateral right cortex and hippocampus after brain injury. Levels of both Par-4 protein and mRNA were significantly increased in the IC and IH as early as 2 h and stayed elevated at 24 and 48 h after injury. These data show that the induction of proapoptotic Par-4 mRNA and protein occurs only in the IC and IH that have been observed to undergo apoptosis and neuronal cell loss after lateral FP brain injury. Because increased expression of Par-4 has been observed to contribute to apoptosis and cell death in cultured neurons, the present temporal pattern of Par-4 expression is consistent with a role for Par-4 in apoptosis and neuronal cell death after traumatic brain injury.

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.

Chromatographic analysis of compounds of pharmaceutical interest.

A set of 17,600 samples belonging to our compound collection is selectively examined by liquid chromatography with UV, evaporative light scattering, and mass spectrometric detection methods. At least 70% of this set consists of pure samples with the expected structures. Subsequent studies by flow injection mass spectrometry show that this value is a conservative estimate and that the actual percentage of pure and correct compounds is close to 80%. Because this is the first time that sample quality information becomes available on such a large scale for the compound collection, it offers an opportunity to perform chemi-informatic studies for which structural integrity is essential. Results of these studies can be used to improve the selection of compounds for screening and evaluate the quality of compounds from particular sources.

Breast cancer surgery: comparing surgical groups and determining individual differences in postoperative sexuality and body change stress.

Women diagnosed and surgically treated for regional breast cancer (N = 190) were studied to determine the sexual and body change sequelae for women receiving modified radical mastectomy (MRM) with breast reconstruction in comparison with the sequelae for women receiving breast-conserving therapy (BCT) or MRM without breast reconstruction. The sexuality pattern for women receiving reconstructive surgery was one that was significantly different--with lower rates of activity and fewer signs of sexual responsiveness--than that for women in either of the other groups. Significantly higher levels of traumatic stress and situational distress regarding the breast changes were reported by the women receiving an MRM in contrast to the women treated with BCT. Using a model to predict sexual morbidity, regression analyses revealed that individual differences in sexual self-schema were related to both sexual and body change stress outcomes.

Differential expression of neurotrophin and neurotrophin receptor mRNAs in and adjacent to fetal midbrain grafts implanted into the dopamine-denervated striatum.

This study examined the expression of neurotrophins and neurotrophin receptors in the lesion/transplanted striatum at four different time points after transplantation. The ventral mesencephalic region was dissected from a single rat fetus at embryonic day 14 (E14) and implanted into the denervated striatum of rats with unilateral 6-hydroxydopamine lesions. Transplanted rats were killed at 1, 2, 3, or 4 weeks after transplantation surgery and the brains subsequently prepared for semiquantitative in situ hybridization analysis of neurotrophin and neurotrophin trk receptors. Hybridization of cRNA probes for trkB or trkC showed a time-dependent reduction within the transplant during the first 4 weeks after transplantation; hybridization of brain-derived neurotrophic factor or tyrosine hydroxylase mRNA probes within the transplant did not change significantly during the same posttransplantation period. Hybridization of the trkB mRNA probe in host striatum adjacent to the transplant was significantly higher than probe hybridization in the corresponding region of the intact striatum during the first 2 weeks after transplantation, but by the 3rd and 4th week, probe hybridization in the denervated/transplanted and intact striatum were the same. Lesioned animals without transplants maintained higher trkB mRNA probe hybridization in the denervated striatum than in the intact striatum at the same postlesion time points suggesting that lesioned/transplanted animals show a normalization of trkB mRNA probe hybridization. Hybridization of the trkC mRNA probe in the lesioned/transplanted striatum was significantly lower than that observed in the intact striatum 4 weeks after transplantation; however, at this same time point we observed a similar reduction of trkC probed hybridization in lesioned animals without transplants. The results of the study show dynamic neurotrophic activity occurring within the transplant and host tissue during the first month of transplant development.

Structure-activity relationships of acyloxyamidine cytomegalovirus DNA polymerase inhibitors.

This paper describes the structure activity relationships of a new class of cytomegalovirus DNA polymerase inhibitors having two aryl groups joined by an acyloxyamidine linker. Examination of a series of analogues in which the terminal groups are varied revealed a very narrow SAR around the 2,4-dichlorophenyl group of the lead compound, but a variety of replacements for the benzothiazole ring are compatible with activity. The most notable of these is the isoxazole ring of compound 78, which provides a 30-fold enhancement in potency compared to the lead compound. We also describe the design, synthesis and evaluation of 10 analogues in which the acyloxyamidine linker is modified or replaced by an isosteric group. Structure-activity relationship studies identified the linker -NH2 group as a critical pharmacophoric element. Ab initio molecular orbital calculations combined with qualitative estimates of steric interaction energies suggest that the lowest energy conformations of the acyloxyamidine linker are characterized by an extended planar CAr-C=N-O-C arrangement and either a syn-periplanar or anti-periplanar N-O-C-C(Ar') arrangement. Only the anti-periplanar conformation was observed in the crystal structures of three acyloxyamidines. The most active of the linker-modified compounds designed on the basis of these studies is the amidine carbamate 20, which is approximately one-third as potent in the cytomegalovirus DNA polymerase inhibition assay as the comparator acyloxyamidine 53. The activity of 20 suggests that acyloxyamidines may bind to the cytomegalovirus DNA polymerase via an anti-periplanar conformation similar to that observed in the crystal structure of acyloxyamidine 36.

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.

Immunohistochemical detection of the lipid peroxidation product 4-hydroxynonenal after experimental brain injury in the rat.

This study examined the accumulation of the cytotoxic lipid peroxidation product 4-hydroxynonenal (HNE) after lateral fluid percussion (FP) brain injury in rats. A diffuse distribution of HNE-immunoreactivity (HNE-ir) was observed in the cortex and hippocampus of the ipsilateral, but not of the contralateral, hemisphere at 30 min, 6 h, 24 h, and 48 h after brain injury. The HNE-ir was well-localized in cell bodies of the ipsilateral cortex and the CA3 pyramidal layer in the ipsilateral hippocampus. Because HNE's interaction with certain proteins causes protein dysfunction and HNE, in vitro, causes neuronal cell damage, the present results suggest that HNE's interaction with neuronal proteins may contribute to neuronal damage in the ipsilateral cortex and hippocampus after brain injury.

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.

Isolation and identification of a major metabolite of PNU-107859, an MMP inhibitor from the biliary fluid of rats.

PNU-107859, an important representative structure in a novel class of matrix metalloproteinases (MMP) inhibitors known as thiadiazoles, was found to be quickly eliminated from rats. A major metabolite (approximately 10% of total dose) was found to be present in the bile of rats. The metabolite in question was isolated and purified from the bile fluids collected from six cannulated rats. From a total of approximately 75 mg of PNU-107859 administered to rats, 3.3 mg of the metabolite was recovered. The NMR and mass spectrometry results indicated that the metabolite is a glucuronide conjugate (1-deoxy-1beta-substituted D-glucopyranosiduronic acid) of the intact drug. Furthermore, the UV, MS, and NMR data established that the conjugate is located at the nitrogen alpha to the thiocarbonyl of the thiadiazole ring.

A new resistance gene, linB, conferring resistance to lincosamides by nucleotidylation in Enterococcus faecium HM1025.

Resistance to lincomycin and clindamycin in the clinical isolate Enterococcus faecium HM1025 is due to a ribosomal methylase encoded by an ermAM-like gene and the plasmid-mediated inactivation of these antibiotics. We have cloned and determined the nucleotide sequence of the gene responsible for the inactivation of lincosamides, linB. This gene encodes a 267-amino-acid lincosamide nucleotidyltransferase. The enzyme catalyzes 3(5'-adenylation) (the adenylation of the hydroxyl group in position 3 of the molecules) of lincomycin and clindamycin. Expression of linB was observed in both Escherichia coli and Staphylococcus aureus. The deduced amino acid sequence of the enzyme did not display any significant homology with staphylococcal nucleotidyltransferases encoded by linA and linA' genes. Sequences homologous to linB were found in 14 other clinical isolates of E. faecium, indicating the spread of the resistance trait in this species.

Glial cell line-derived neurotrophic factor improves survival of dopaminergic neurons in transplants of fetal ventral mesencephalic tissue.

This study was designed to determine whether or not an exogenous source of glial cell line-derived neurotrophic factor (GDNF) could be delivered continuously into the denervated/transplanted striatum and stimulate the survival, growth, and function of fetal ventral mesencephalic tissue transplants. Adult male rats with unilateral 6-hydroxydopamine lesions received transplants of fetal ventral mesencephalic tissue into the denervated striatum. Immediately thereafter, osmotic pumps [Alzet 2002, 0.5 microliter/h] were attached to intracerebral cannula and either a citrate buffer alone [control] or r-methuGDNF [dissolved in sodium citrate buffer to a concentration of 0.45 microgram/microliter] was infused into a site approximately 1.0 mm lateral to the transplant for a 2-week period; one group of lesioned animals did not receive transplants but was infused with GDNF. The effect of GDNF on tyrosine hydroxylase-positive (TH+) fiber outgrowth from transplants was variable, and image analysis revealed no significant difference between the GDNF and citrate groups. In contrast, the mean number of TH+ cells bodies in transplants infused with GDNF [2,037 +/- 149, n = 8] vs citrate [663 +/- 160, n = 8] was statistically significant (P < 0.001); cell counts were made in every third brain section [35 micrometer]. Similarly, transplants infused with GDNF showed an over-compensatory effect to amphetamine-induced rotational behavior that was significantly lower than that observed in transplanted animals receiving citrate buffer infusions. Infusions of GDNF into the denervated striatum alone had no significant effect on amphetamine-induced rotational behavior or on TH fiber morphology in the lesioned striatum. Thus, a continuous infusion of GDNF can improve the survivability of dopaminergic neurons in transplants of fetal ventral mesencephalic tissue.

Optimal effectiveness of BDNF for fetal nigral transplants coincides with the ontogenic appearance of BDNF in the striatum.

Transplantation of fetal nigral dopamine neurons into the caudate and putamen of Parkinson's disease patients produces limited symptomatic relief. One approach to augment the outgrowth and function of nigral grafts includes exposure of the graphs to neurotrophic factors; however, the temporal requirements for optimizing these actions are unknown. The present study characterized the ontogeny of brain-derived neurotrophic factor (BDNF) in the rat striatum and used this information to define and evaluate three distinct periods of BDNF infusion into fetal nigral grafts transplanted into the striatum of rats with experimental Parkinson's disease. At postnatal day 1 (P1), BDNF and dopamine were measured at 17 and 27% of peak levels, respectively, that occurred at P27 for both. Both compounds showed their greatest surge between P7 and P20, increasing from 40% to approximately 95% of peak levels. Exogenous BDNF infused into transplants during weeks 1 and 2 after the transplantation, which coincide with the developmental period embryonic day 14 (E14)-P7 for transplanted tissue, did not improve rotational behavior or enhance fiber outgrowth of transplanted dopamine neurons. Delaying the BDNF infusion until transplanted tissue was approximately P8-P21 greatly enhanced the effect on rotational behavior and doubled the area of dopamine fiber outgrowth from the transplants. Delaying the infusion until transplanted tissue was approximately P36-P49 failed to augment fiber outgrowth and decreased the behavioral function of transplants. Thus, the optimal effect of exogenous BDNF on the development of dopamine neurons in fetal nigral transplants occurs at a postnatal age when endogenous dopamine and BDNF show the greatest increases during the normal development of the striatum.

Age-related decline in striatal dopamine release and motoric function in brown Norway/Fischer 344 hybrid rats.

The Brown Norway/Fischer 344 F1 hybrid rats (F344BNF1) is a newer rat model and is emerging as an important rodent model of aging. In the present study we used motoric performance tests, intracerebral microdialysis, and neurochemical measures of postmortem brain tissue to investigate the effects of aging in young (4-5 months), middle-aged (18-19), and old (24-25 months) F344BNF1 hybrid rats. We observed that old F344BNF1 rats exhibited decreased motoric performance, and lower levels of spontaneous and d-amphetamine-induced locomotor activity than those observed in young F344BNF1 rats. Microdialysis measures of extracellular basal levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 4-hydroxy-3-methoxyphenylacetic acid (HVA) were significantly diminished in the striata of the middle-aged and old rats as compared to levels in young animals. In addition, d-amphetamine-evoked overflow of DA was significantly decreased in the middle-aged and aged rat striatum as compared to DA overflow in young F344BNF1 rats. Studies of postmortem brain tissue showed that the changes in overflow of DA correlated with significantly lower DA tissue content in ventral striatum and midbrain. Moreover, both dopamine turnover ratios (DOPAC/DA, HVA/DA) and the serotonin turnover ratio (5-HIAA/5-HT) were significantly elevated in the ventral striatum and nucleus accumbens. The results of this study demonstrate a correlation between reductions in striatal DA neurochemistry and diminished motor function in aged F344BNF1 rats.