Biomedical subjects

A C Granholm

Publications and source records attributed to A C Granholm.

At least 19 recordsLinked to original sources

PubMed2001

Effects of age and GDNF on noradrenergic innervation of the hippocampal formation: studies from intraocular grafts.

Recent studies have suggested that factors in the target tissue influence the degree of plasticity and regeneration following aging and/or specific insults. We have investigated whether young or aged targets differ in their noradrenergic innervation from fetal locus coeruleus (LC) neurons, and also if a specific growth factor, glial cell line-derived neurotrophic factor (GDNF) can affect this innervation pattern. Tissue pieces of fetal brainstem and young (3 months) or old (18 months) iris tissue were transplanted simultaneously into the anterior chamber of the eye of adult hosts. We found that aged iris transplants became innervated to a significantly lesser degree by the cografted LC neurons than young iris transplants. Fetal hippocampal tissue was then grafted to adult hosts, and a fetal brainstem graft containing LC neurons was placed adjacent to the first graft, either at 3 or 21 months post-grafting. Thus, old/young chimeras of the noradrenergic coeruleo-hippocampal pathway were created. Aged hippocampal grafts received a much less dense innervation from co-grafted LC neurons than young hippocampal grafts. Tyrosine hydroxylase-positive-immunoreactive innervation was only found in the outskirts of aged grafts, while the young hippocampal grafts contained an even innervation pattern. The innervation density of hippocampal grafts was significantly enhanced by GDNF treatment. These findings demonstrate that target-derived factors may regulate neuronal plasticity, and that the age of the target is more important for innervation properties than the age of the neuron innervating a particular target.

Aging↗

PubMed2001

GDNF improves cerebellar Purkinje neuron function in aged F344 rats.

Aging is associated with a decline in the function of beta-adrenergic receptor responses in the cerebellum. This decline in noradrenergic receptor sensitivity may underlie some of the accompanying age-related declines in motoric learning behaviors. Glial cell line-derived neurotrophic factor (GDNF) has been reported to prevent the degeneration of noradrenergic neurons following neurotoxic lesions. Thus, it was of interest to examine if GDNF would have a beneficial effect on age-related declines in noradrenergic function. Eighteen-month-old F344 rats were injected with 500 microg GDNF in 20 microl into the cisterna magna. Three weeks following GDNF or vehicle treatment, rats were tested on a motor coordination task and then examined electrophysiologically under urethane anesthesia. GDNF did not produce an improvement in performance on an inclined balance beam or an accelerating rotorod. In young (3-month-old) F344 rats isoproterenol (ISO) will increase GABAergic inhibitions in the majority of cells examined; however, in aged rats only about 30% of neurons demonstrate this phenotype. In the aged rats treated with GDNF, ISO was able to increase GABAergic inhibitions in greater than 75% of the neurons tested, thus returning the neurons to a young phenotype. We examined the brains for expression of bcl-2, which has been shown to be increased in the aged cerebellum. GDNF was able to down-regulate this neuronal signal. Thus, intra-cisterna magna delivery of GDNF to aged rats improved beta-adrenergic receptor function and reduced stress related signaling of bcl-2 in the aged F344 rats to a level similar to that observed in young rats.

Aging↗

PubMed2001

Intranigral transplantation of solid tissue ventral mesencephalon or striatal grafts induces behavioral recovery in 6-OHDA-lesioned rats.

Parkinson's disease (PD) is characterized by a degeneration of the dopamine (DA) pathway from the substantia nigra (SN) to the basal forebrain. Prior studies in unilateral 6-hydroxydopamine (6-OHDA)-lesioned rats have primarily concentrated on the implantation of fetal ventral mesencephalon (VM) into the striatum in attempts to restore DA function in the target. We implanted solid blocks of fetal VM or fetal striatal tissue into the SN to investigate whether intra-nigral grafts would restore motor function in unilaterally 6-OHDA-lesioned rats. Intra-nigral fetal striatal and VM grafts elicited a significant and long-lasting reduction in apomorphine-induced rotational behavior. Lesioned animals with ectopic grafts or sham surgery as well as animals that received intra-nigral grafts of fetal cerebellar cortex showed no recovery of motor symmetry. Subsequent immunohistochemical studies demonstrated that VM grafts, but not cerebellar grafted tissue expressed tyrosine hydroxylase (TH)-positive cell bodies and were associated with the innervation by TH-positive fibers into the lesioned SN as well as adjacent brain areas. Striatal grafts were also associated with the expression of TH-positive cell bodies and fibers extending into the lesioned SN and an induction of TH-immunolabeling in endogenous SN cell bodies. This finding suggests that trophic influences of transplanted fetal striatal tissue can stimulate the re-expression of dopaminergic phenotype in SN neurons following a 6-OHDA lesion. Our data support the hypothesis that a dopaminergic re-innervation of the SN and surrounding tissue by a single solid tissue graft is sufficient to improve motor asymmetry in unilateral 6-OHDA-lesioned rats.

Animals↗

PubMed2001

Neuroprotection of grafted neurons with a GDNF/caspase inhibitor cocktail.

Transplantation of fetal ventral mesencephalic (VM) tissue shows great promise as an experimental therapy for patients with Parkinson's disease. However, cell survival in brain tissue grafts is poor, with survival rates of only 5-15%. We have utilized a combination of the caspase inhibitor bocaspartyl (OMe)-fluoromethylketone (BOC-ASP-CH2F) and glial cell line-derived neurotrophic factor (GDNF) to enhance survival of grafted dopamine neurons. The VM tissue was dissected from embryonic day 13-15 rat fetuses, incubated in different doses of BOC-ASP-CH2F and GDNF, and transplanted to the anterior chamber of the eye of adult rats. Growth of the tissue was assessed through the translucent cornea. Doses of 50 and 100 micromolar of the general caspase inhibitor appeared to have detrimental effects on mesencephalic tissue, while 20 micromolar had beneficial effects on overall transplant growth. A combination of the caspase inhibitor and GDNF appeared to have more prominent effects on cell survival as well as dopaminergic fiber density than either agent by itself. The transplants doubled in size when they were treated with a combination of BOC-ASP-CH2F and GDNF, and cell death markers were significantly reduced at both 48 h and 4-6 days postgrafting. This is, to our knowledge, the first combined approach using apoptotic blockers with trophic factors, and demonstrates a viable strategy for protection of developing neurons, since several different aspects of graft function may be addressed simultaneously.

Animals↗

PubMed2000

Time course of degenerative alterations in nigral dopaminergic neurons following a 6-hydroxydopamine lesion.

The neurotoxin 6-hydroxydopamine (6-OHDA) has been used extensively in animal models of Parkinson's disease. Typically, rodents develop severe unilateral movement deficiencies coupled with apomorphine-induced rotation behavior at least 1 week after an ipsilateral 6-OHDA lesion of the nigrostriatal dopamine (DA) system. The short-term morphological effects of 6-OHDA have not been determined in detail, however, and the exact process by which neurons die has not been elucidated. Thus, novel degenerative markers were used to determine the temporal pattern of acute phenotypic and degenerative alterations following a unilateral 6-OHDA injection into the medial forebrain bundle of adult rats. 6-Hydroxydopamine administration resulted in an increase in terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining as early as 6 hours postlesion. Staining for FluoroJade, a marker of neuronal degeneration, was evident at all time points examined but was maximal at 48 hours. Loss of tyrosine hydroxylase (TH) immunoreactivity began in axons at 6 hours, and progressed to cell bodies at later time points postlesion. Morphological examination of these neurons supported the conclusion of their death via apoptosis. Thus, whereas behavioral manifestations typically become evident 1 week or more following a 6-OHDA lesion, it is evident that nigral cell degeneration begins much earlier. This suggests multiple therapeutic possibilities, including the prevention of apoptosis, in affected neurons.

Animals↗

PubMed2000

Glial cell line-derived neurotrophic factor is essential for postnatal survival of midbrain dopamine neurons.

Glial cell line-derived neurotrophic factor (GDNF) is one of the most potent trophic factors that have been identified for midbrain dopamine (DA) neurons. Null mutations for trophic factor genes have been used frequently for studies of the role of these important proteins in brain development. One problem with these studies has been that often only prenatal development can be studied because many of the knockout strains, such as those with GDNF null mutations, will die shortly after birth. In this study, we looked at the continued fate of specific neuronal phenotypes from trophic factor knockout mice beyond the time that these animals die. By transplanting fetal neural tissues from GDNF -/-, GDNF +/-, and wild-type (WT) mice into the brain of adult wild-type mice, we demonstrate that the continued postnatal development of ventral midbrain dopamine neurons is severely disturbed as a result of the GDNF null mutation. Ventral midbrain grafts from -/- fetuses have markedly reduced DA neuron numbers and fiber outgrowth. Moreover, DA neurons in such transplants can be "rescued" by immersion in GDNF before grafting. These findings suggest that postnatal survival and/or phenotypic expression of ventral mesencephalic DA neurons is dependent on GDNF. In addition, we present here a strategy for studies of maturation and even aging of tissues from trophic factor and other knockout animals that do not survive past birth.

Animals↗

PubMed2000

Loss of cholinergic phenotype in basal forebrain coincides with cognitive decline in a mouse model of Down's syndrome.

Mice with segmental trisomy of chromosome 16 (Ts65Dn) have been used as a model for Down's syndrome. These mice are born with a normal density of basal forebrain cholinergic neurons but, like patients with Down's syndrome, undergo a significant deterioration of these neurons later in life. The time course for this degeneration of cholinergic neurons has not been studied, nor is it known if it correlates with the progressive memory and learning deficits described. Ts65Dn mice that were 4, 6, 8, and 10 months old were sacrificed for evaluation of basal forebrain morphology. Separate groups of mice were tested on visual or spatial discrimination learning and reversal. We found no alterations in cholinergic markers in 4-month-old Ts65Dn mice, but thereafter a progressive decline in density of cholinergic neurons, as well as significant shrinkage of cell body size, was seen. A parallel loss of staining for the high-affinity nerve growth factor receptor, trkA, was observed at all time points, suggesting a biological mechanism for the cell loss involving this growth factor. Other than transient difficulty in learning the task requirements, there was no impairment of trisomic mice on visual discrimination learning and reversal, whereas spatial learning and reversal showed significant deficits, particularly in the mice over 6 months of age. Thus, the loss of ChAT-immunoreactive neurons in the basal forebrain was coupled with simultaneous deficits in behavioral flexibility on a spatial task occurring for the first time around 6 months of age. These findings suggest that the loss of cholinergic function and the simultaneous decrease in trkA immunoreactivity in basal forebrain may directly correlate with cognitive impairment in the Ts65Dn mouse

Animals↗

PubMed2000

Long-term environmental enrichment leads to regional increases in neurotrophin levels in rat brain.

A number of studies have demonstrated that both morphological and biochemical indices in the brain undergo alterations in response to environmental influences. In previous work we have shown that rats raised in an enriched environmental condition (EC) perform better on a spatial memory task than rats raised in isolated conditions (IC). We have also found that EC rats have a higher density of immunoreactivity than IC rats for both low and high affinity nerve growth factor (NGF) receptors in the basal forebrain. In order to determine if these alterations were coupled with altered levels of neurotrophins in other brain regions as well, we measured neurotrophin levels in rats that were raised in EC or IC conditions. Rats were placed in the different environments at 2 months of age and 12 months later brain regions were dissected and analyzed for NGF, brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) levels using Promega ELISA kits. We found that NGF and BDNF levels were increased in the cerebral cortex, hippocampal formation, basal forebrain, and hindbrain in EC animals compared to age-matched IC animals. NT-3 was found to be increased in the basal forebrain and cerebral cortex of EC animals as well. These findings demonstrate significant alterations in NGF, BDNF, and NT-3 protein levels in several brain regions as a result of an enriched versus an isolated environment and thus provide a possible biochemical basis for behavioral and morphological alterations that have been found to occur with a shifting environmental stimulus.

Animals↗

PubMed2000

Oestrogen and nerve growth factor - neuroprotection and repair in Alzheimer's disease.

The neurogenetics and neuropathology of Alzheimer's disease (AD) are still largely unknown, even though recent work has clarified some genetic components in this common and devastating neurodegenerative disease. Most of the genetic mutations have been shown to be, at least in the early onset type of AD, related to the function of a large transmembrane protein, amyloid precursor protein (APP). This protein is cleaved into various smaller fragments that are either soluble or aggregating. It is thought that this processing of APP is inherently important for the initiation and progression of AD. Recent animal models have suggested that it is not the formation of beta-amyloid plaques per se, but the altered processing of APP and the subsequent loss of soluble APP, that sets the stage for the massive neuronal cell loss which occurs in AD. We would like to propose a three-way relationship between oestrogen, APP and nerve growth factor (NGF) in the neural pathways of the brain which are involved in learning and memory - the limbic system. The degeneration of the cholinergic innervation from the basal forebrain to the hippocampal formation in the temporal lobe is thought to be one of the factors determining the progression of memory decay, both during normal ageing and AD. Oestrogen and NGF are among the neuroprotective agents that have shown some potential for the treatment of AD. Previous results of treatment with these two agents and their relationship to the amyloid proteins, will be discussed in this review.

Alzheimer Disease↗

PubMed1999

Anatomical distribution of glycoprotein 93 (gp93) on nerve fibers during rat brain development.

Recent studies have implicated glycoconjugates on the membrane of growth cones as the necessary markers and intermediaries for axonal recognition, axonal motility, and pathway development. One such glycoconjugate, glycoprotein 93 (gp93), has been characterized, but the relative distribution of gp93 has yet to be described for the embryonic brain. In this study, the anatomical distribution of gp93 has been analyzed at embryonic day 15 (E15) and E18, and on postnatal day 3 in the rat by using a polyclonal gp93 antibody. Furthermore, fetal brain tissue transplanted into the adult rat eye has been tested for gp93 immunoreactivity, since central noradrenergic neurons in brainstem transplants are known to provide a continuous source of growing axons, even in adult tissue. In general, a greater abundance of gp93 immunoreactivity is apparent in the earlier embryonic stages (E15 and E18), whereas less is seen in the postnatal brain. The regions showing unique dispersal patterns of gp93 are the neuroepithelium, cerebral cortex, septo-hippocampal pathways, brainstem, and midbrain. This study has therefore focused on these areas and found implications for gp93 distribution appearing in the early development of specific neuronal pathways. Moreover, axons stain densely for gp93 within brain tissue transplants. The presence of gp93 in areas of extensive axonal outgrowth in the normal brain and in transplants suggests that this antibody is used as an early marker for axonal growth. Furthermore, gp93 might be used to map normal development in order to improve our understanding of diseases arising from developmental abnormalities.

Animals↗

PubMed1999

Changes in brain nerve growth factor levels and nerve growth factor receptors in rats exposed to environmental enrichment for one year.

This study examined the effects of long-term differential rearing on levels of brain nerve growth factor, its receptors, and their relationships to cognitive function. Adult rats (two months old) were placed into either enriched or standard housing conditions where they remained for 12 months. Animals from the enriched condition group had significantly higher levels of nerve growth factor in hippocampus, visual and entorhinal cortices compared with animals housed in isolated condition. Immunohistochemical analysis of brain tissue from the medial septal area revealed higher staining intensity and fibre density with both the low-affinity and the high-affinity nerve growth factor receptors. Enriched rats performed better than isolated rats in acquisition of spatial learning and had lower locomotion scores in the open field. These results provide further evidence that experimental stimulation results in increased production of trophic factors and structural reorganization in specific brain regions known to be involved in cognitive function.

Age Factors↗

PubMed1998

The hyaluronan receptor RHAMM in noradrenergic fibers contributes to axon growth capacity of locus coeruleus neurons in an intraocular transplant model.

The hyaluronan receptor for hyaluronic acid-mediated motility (RHAMM) plays a role in cell migration and motility in many systems. Recent observations on the involvement of RHAMM in neurite motility in vitro suggest that it might also be important in axon outgrowth in situ. This was addressed directly by investigating both RHAMM expression in the rat CNS and the ability of anti-RHAMM reagents to interfere with tissue growth and axon outgrowth in intraocular brainstem transplants. By western blotting, anti-RHAMM antibody detected a RHAMM isoform of 75,000 mol. wt in both whole brain homogenate and synaptosome preparations, and a 65,000 mol. wt isoform in synaptosomes. Immunofluorescence of adult brain sections revealed RHAMM-like immunoreactivity in varicose fibers that were also positive for the noradrenergic marker dopamine-beta-hydroxylase. Not all noradrenergic fibers contained RHAMM, nor was RHAMM detected in other monoaminergic fiber types. Lesions of noradrenergic fiber systems with beta-halobenzylamine-N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) eliminated RHAMM-positive fibers, but noradrenergic axons that sprouted extensively after this treatment were strongly RHAMM-positive. To assess RHAMM's role in fiber outgrowth, fetal brainstem tissue containing noradrenergic neurons was grafted into the anterior chamber of the eye. Treatment of grafts with anti-RHAMM antibody caused significant inhibition of tissue growth and axon outgrowth, as did a peptide corresponding to a hyaluronan binding domain of RHAMM. These agents had no such effects on transplants containing serotonergic and dopaminergic neurons. These results suggest that RHAMM, an extracellular matrix receptor previously shown to contribute to migratory and contact behavior of cells, may also be important in the growth and/or regenerative capacity of central noradrenergic fibers originating from the locus coeruleus.

Animals↗

PubMed1998

A non-invasive system for delivering neural growth factors across the blood-brain barrier: a review.

Intraventricular administration of nerve growth factor (NGF) in rats has been shown to reduce age-related atrophy of central cholinergic neurons and the accompanying memory impairment, as well as protect these neurons against a variety of perturbations. Since neurotrophins do not pass the blood-brain barrier (BBB) in significant amounts, a non-invasive delivery system for this group of therapeutic molecules needs to be developed. We have utilized a carrier system, consisting of NGF covalently linked to an anti-transferrin receptor antibody (OX-26), to transport biologically active NGF across the BBB. The biological activity of this carrier system was tested using in vitro bioassays and intraocular transplants; we were able to demonstrate that cholinergic markers in both developing and aged intraocular septal grafts were enhanced by intravenous delivery of the OX-26-NGF conjugate. In subsequent experiments, aged (24 months old) Fischer 344 rats received intravenous injections of the OX-26-NGF conjugate for 6 weeks, resulting in a significant improvement in spatial learning in previously impaired rats, but disrupting the learning ability of previously unimpaired rats. Neuroanatomical analyses showed that OX-26-NGF conjugate treatment resulted in a significant increase in cholinergic cell size as well as an upregulation of both low and high affinity NGF receptors in the medial septal region of rats initially impaired in spatial learning. Finally, OX-26-NGF was able to protect striatal cholinergic neurons against excitotoxicity and basal forebrain cholinergic neurons from degeneration associated with chemically-induced loss of target neurons. These results indicate the potential utility of the transferrin receptor antibody delivery system for treatment of neurodegenerative disorders with neurotrophic substances.

Animals↗

PubMed1997

Carrier mediated delivery of NGF: alterations in basal forebrain neurons in aged rats revealed using antibodies against low and high affinity NGF receptors.

The distribution of low and high affinity nerve growth factor (NGF) receptors was investigated in the basal forebrain during aging and NGF treatment. A peripheral administration model for NGF was utilized. NGF was conjugated to a transferrin receptor antibody (OX-26-NGF), and this conjugate was injected into the tail vein of aged Fischer 344 male rats (24 months) twice weekly for 5 weeks (equivalent to 50 microg of NGF/injection). Controls were injected with a non-conjugated mixture of OX-26 and NGF. The aged rats treated with conjugate showed a significant increase in cell size of p75- and trkA-immunoreactive neurons in the medial septal nucleus and vertical limb of the diagonal band as compared to controls. A significant increase in cell size of trkA-immunoreactive neurons was also observed in the horizontal limb of the diagonal band in rats treated with conjugate. Rats treated with conjugate also showed a significant increase in overall staining density for p75 and trkA antibodies in the medial septal nucleus as compared to controls. A significant increase in staining density of p75-immunoreactive structures was also observed in the vertical and horizontal limbs of the diagonal band. Therefore, treatment with OX-26-NGF conjugate has regional effects on both the low and high affinity NGF receptors in terms of cell body size and staining density in the basal forebrain of aged rats. The current findings support the idea that this delivery system might be useful in therapeutic approaches involving the delivery of neurotrophic factors and other large molecules into the brain.

Aging↗

PubMed1997

A non-invasive transport system for GDNF across the blood-brain barrier.

Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophin which supports midbrain dopaminergic neurons and spinal cord motorneurons. GDNF has been proposed as a possible therapeutic agent for Parkinson's disease, spinal cord injury or motorneuron degenerative disorders. Administration of GDNF is complicated by its poor penetration across the blood-brain barrier (BBB). Central nervous system capillaries are uniquely enriched in transferrin receptors and antibodies to these receptors (OX-26) have been proposed as potential carriers to transport large molecules across the BBB. Intravenous administration of an OX-26-GDNF conjugate enhanced survival of spinal cord motorneurons in intraocular transplants, which possess an organotypic BBB. This suggests that the OX-26-GDNF conjugate could be utilized for non-invasive treatment of neurodegenerative diseases of the spinal cord or midbrain dopaminergic neurons.

Animals↗

PubMed1997

Morphological alterations in the peripheral and central nervous systems of mice lacking glial cell line-derived neurotrophic factor (GDNF): immunohistochemical studies.

Glial cell line-derived neurotrophic factor (GDNF) is a member of the TGF-beta superfamily of growth factors with neurotrophic activity on midbrain dopaminergic neurons and on developing and mature motoneurons of the brainstem and spinal cord. To investigate the extent of GDNF dependency of central and peripheral nervous structures during development, we have performed an immunohistochemical analysis of sections from the whole head including brain, peripheral ganglia, developing teeth and tongue, as well as intestines, in mutant mice lacking a part of the third exon that encodes the GDNF protein. As described previously, these null-mutated mice lack most of the enteric nerve plexus and are subject to agenesis or severe dysgenesis of the kidneys. In the present communication, we examined the development of vibrissae and incisor and molar teeth, as well as the innervation of these structures, and found no differences between null-mutated and control mice. A decrease in the immunohistochemical labeling intensity with tyrosine hydroxylase was observed in the superior cervical ganglion (SCG), as well as in the pontine nucleus locus coeruleus, and the sympathetic innervation of blood vessels and glands in the head was significantly decreased. None of the brain nuclei studied exhibited any significant decreases in the total number of neurons, but the packing density of neurons in the nucleus locus coeruleus was decreased. These data indicate that GDNF might be one neurotrophic factor that contributes to the development of central and peripheral noradrenergic neurons.

Animals↗

PubMed1997

Collateral sprouting of central noradrenergic neurons during aging: histochemical and neurochemical studies in intraocular triple transplants.

The sprouting capacity of aged noradrenergic neurons of the brain-stem nucleus locus coeruleus (LC) was examined using intraocular transplants of fetal tissues. Fetal hippocampal tissue (E18) and LC tissue (E15) were transplanted together as a double transplant into the anterior chamber of the eye of young adult Fischer 344 rats. The double transplants were allowed to mature for 14-18 months, after which an additional fetal hippocampal transplant was placed next to the LC graft. The triple transplants were monitored for overall growth and vascularization for an additional 2-6 months. Immunohistochemical examinations showed that both young (2-6 months old) and aged (16-24 months old) hippocampal cografts contained a plexus of thin varicose tyrosine hydroxylase (TH)-immunoreactive fibers extending throughout the grafted hippocampal tissues. However, the aged hippocampal grafts contained a denser uniform plexus of TH-positive fibers compared to the young transplants. Immunohistochemistry with synapsin antibodies demonstrated that both the young and the aged hippocampal transplants contained much higher densities of synaptic elements than the LC grafts. In vivo electrochemical measurements of potassium-evoked overflow of norepinephrine (NE) in the grafts showed that similar amounts of NE overflow were detected in both the young and the aged hippocampal grafts. HPLC-EC measurements of NE levels in the grafts revealed that there were similar amounts of NE in the young and the aged grafts, and the grafts did not contain serotonin or dopamine. In summary, the findings of the present study show that aged LC neurons are capable of undergoing collateral sprouting producing a functional NE neuronal system when introduced to an appropriate young target.

Animals↗

PubMed1997

Glial cell line-derived neurotrophic factor improves survival of ventral mesencephalic grafts to the 6-hydroxydopamine lesioned striatum.

One approach to replace lost dopaminergic neurons in Parkinson's disease is to transplant fetal mesencephalic tissue into the striatum. In an attempt to expand the developmental window useful for grafting of mesencephalic tissue and increase the fiber outgrowth from grafted dopaminergic neurons, we have pretreated fetal mesencephalic tissue with the dopaminotrophic factor glial cell line-derived neurotrophic factor (GDNF). Mesencephalic tissue pieces from embryonic day 18-19 Fischer 344 rats were preincubated for 20 min with GDNF (1 microg/microl) or vehicle. Two tissue pieces were then transplanted into the striatum of rats that had been unilaterally lesioned by medial forebrain bundle injections of 6-hydroxydopamine. The animals were tested for apomorphine-induced rotations prior to intracranial grafting. Host rats received intrastriatal injections of 10 microg GDNF or control solution at 10 days and 4 weeks postgrafting. The animals were tested in the rotometer twice monthly following transplantation. Despite the fact that these transplants were from a suboptimal donor stage, the rotations were significantly decreased in both transplanted groups. Immunohistochemical evaluation of the host brains revealed that the overall size of transplanted mesencephalic tissue was significantly increased in the GDNF-treated animals, and that the average size of transplanted tyrosine hydroxylase (TH)-positive neurons was also increased. Furthermore, we found that the innervation density of surrounding host striatal tissue was significantly increased in the GDNF-treated group, as compared with controls. Taken together, these results suggest that treatment of intrastriatal ventral mesencephalon grafts with GDNF can optimize the conditions for intracranial grafting and thus improve the chances for functional recovery following the intrastriatal grafting procedure.

Animals↗