Advances in stem cell and other therapies for Huntington's disease: An update.

Huntington's disease (HD) is a neurodegenerative disorder caused by an autosomal dominant mutation leading to an abnormal CAG repeat expansion. The result is the synthesis of a toxic misfolded protein, called the mutant huntingtin protein (mHTT). Most current treatments are palliative, but the latest research has expanded into multiple modalities, including stem cells, gene therapy, and even the use of 3D cell structures, called organoids. Stem cell research as a treatment for HD has included the use of various types of stem cells, such as mesenchymal stem cells, neural stem cells, embryonic stem cells, and even reprogrammed stem cells called induced pluripotent stem cells. The goal has been to develop stem cell transplant grafts that will replace the existing mutated neurons, as well as release existing trophic factors for neuronal support. Additionally, research in gene modification using CRISPR-Cas9, PRIME editing, and other forms of genetic modifications are continuing to evolve. Most recently, advancements in stem cell modeling have yielded 3D stem cell tissue models, called organoids. These organoids offer the unique opportunity to transplant a structured stem cell graft which, ideally, models normal human brain tissue more accurately. This manuscript summarizes the recent research in stem cells, genetic modifications, and organoids as a potential for treatment of HD.

Crevasse refreezing and signatures of retreat observed at Kamb Ice Stream grounding zone.

Ice streams flowing into Ross Ice Shelf are presently responsible for around 10% of the mass flux from West Antarctica, with the noteworthy exception of Kamb Ice Stream, which stagnated in the late 1800s. The subsequent reduction in ice supply led to grounding-line retreat at the coastal margin where Kamb transitions into the floating Ross Ice Shelf. Grounding-line migration is linked to broader changes in ice-sheet mass balance and sea level, but our understanding of related ice, ocean and seafloor interactions is limited by the difficulty in accessing these remote regions. Here we report in situ observations from an underwater vehicle deployed at Kamb that show how fine-scale variability in ice and ocean structure combine to influence a diversity of ice-ocean interactions. We found a stratified water column within a tenth of a degree of freezing at the ice base and mapped basal crevasses with supercooled water and active marine ice formation. At the seafloor, we interpret parallel ridges as crevasse impressions left as the ice lifted off during grounding-line retreat. These observations from a recently ungrounded sub-shelf environment illuminate both the geomorphological signatures of past grounding-line retreat and the fine-scale sensitivity of ongoing ice-ocean interactions to ice topography.

The amplitude and origin of sea-level variability during the Pliocene epoch.

Earth is heading towards a climate that last existed more than three million years ago (Ma) during the 'mid-Pliocene warm period'1, when atmospheric carbon dioxide concentrations were about 400 parts per million, global sea level oscillated in response to orbital forcing2,3 and peak global-mean sea level (GMSL) may have reached about 20 metres above the present-day value4,5. For sea-level rise of this magnitude, extensive retreat or collapse of the Greenland, West Antarctic and marine-based sectors of the East Antarctic ice sheets is required. Yet the relative amplitude of sea-level variations within glacial-interglacial cycles remains poorly constrained. To address this, we calibrate a theoretical relationship between modern sediment transport by waves and water depth, and then apply the technique to grain size in a continuous 800-metre-thick Pliocene sequence of shallow-marine sediments from Whanganui Basin, New Zealand. Water-depth variations obtained in this way, after corrections for tectonic subsidence, yield cyclic relative sea-level (RSL) variations. Here we show that sea level varied on average by 13 ± 5 metres over glacial-interglacial cycles during the middle-to-late Pliocene (about 3.3-2.5 Ma). The resulting record is independent of the global ice volume proxy3 (as derived from the deep-ocean oxygen isotope record) and sea-level cycles are in phase with 20-thousand-year (kyr) periodic changes in insolation over Antarctica, paced by eccentricity-modulated orbital precession6 between 3.3 and 2.7 Ma. Thereafter, sea-level fluctuations are paced by the 41-kyr period of cycles in Earth's axial tilt as ice sheets stabilize on Antarctica and intensify in the Northern Hemisphere3,6. Strictly, we provide the amplitude of RSL change, rather than absolute GMSL change. However, simulations of RSL change based on glacio-isostatic adjustment show that our record approximates eustatic sea level, defined here as GMSL unregistered to the centre of the Earth. Nonetheless, under conservative assumptions, our estimates limit maximum Pliocene sea-level rise to less than 25 metres and provide new constraints on polar ice-volume variability under the climate conditions predicted for this century.

Transplantation of mesenchymal stem cells genetically engineered to overexpress interleukin-10 promotes alternative inflammatory response in rat model of traumatic brain injury.

BACKGROUND: Traumatic brain injury (TBI) is a major cause for long-term disability, yet the treatments available that improve outcomes after TBI limited. Neuroinflammatory responses are key contributors to determining patient outcomes after TBI. Transplantation of mesenchymal stem cells (MSCs), which release trophic and pro-repair cytokines, represents an effective strategy to reduce inflammation after TBI. One such pro-repair cytokine is interleukin-10 (IL-10), which reduces pro-inflammatory markers and trigger alternative inflammatory markers, such as CD163. In this study, we tested the therapeutic effects of MSCs that were engineered to overexpress IL-10 when transplanted into rats following TBI in the medial frontal cortex. METHODS: Thirty-six hours following TBI, rats were transplanted with MSCs and then assessed for 3 weeks on a battery of behavioral tests that measured motor and cognitive abilities. Histological evaluation was then done to measure the activation of the inflammatory response. Additionally, immunomodulatory effects were evaluated by immunohistochemistry and Western blot analyses. RESULTS: A significant improvement in fine motor function was observed in rats that received transplants of MSCs engineered to overexpress IL-10 (MSCs + IL-10) or MSCs alone compared to TBI + vehicle-treated rats. Although tissue spared was unchanged, anti-inflammatory effects were revealed by a reduction in the number of glial fibrillary acidic protein cells and CD86 cells in both TBI + MSCs + IL-10 and TBI + MSC groups compared to TBI + vehicle rats. Microglial activation was significantly increased in the TBI + MSC group when compared to the sham + vehicle group. Western blot data suggested a reduction in tumor necrosis factor-alpha in the TBI + MSCs + IL-10 group compared to TBI + MSC group. Immunomodulatory effects were demonstrated by a shift from classical inflammation expression (CD86) to an alternative inflammation state (CD163) in both treatments with MSCs and MSCs + IL-10. Furthermore, co-labeling of both CD86 and CD163 was detected in the same cells, suggesting a temporal change in macrophage expression. CONCLUSIONS: Overall, our findings suggest that transplantation of MSCs that were engineered to overexpress IL-10 can improve functional outcomes by providing a beneficial perilesion environment. This improvement may be explained by the shifting of macrophage expression to a more pro-repair state, thereby providing a possible new therapy for treating TBI.

Glucose variability and inner retinal sensory neuropathy in persons with type 1 diabetes mellitus.

PurposeTo quantify early neuroretinal alterations in patients with type 1 diabetes mellitus (T1DM) and to assess whether glycemic variability contributes to alterations in neuroretinal structure or function.MethodsThirty patients with T1DM and 51 controls underwent comprehensive ophthalmic examination and assessment of retinal function or structure with frequency doubling perimetry (FDP), contrast sensitivity, dark adaptation, fundus photography, and optical coherence tomography (OCT). Diabetic participants wore a subcutaneous continuous glucose monitor for 5 days, from which makers of glycemic variability including the low blood glucose index (LGBI) and area under the curve (AUC) for hypoglycemia were derived.ResultsSixteen patients had no diabetic retinopathy (DR), and 14 had mild or moderate DR. Log contrast sensitivity for the DM group was significantly reduced (mean±SD=1.63±0.06) compared with controls (1.77±0.13, P<0.001). OCT analysis revealed that the inner temporal inner nuclear layer (INL) was thinner in patients with T1DM (34.9±2.8 µm) compared with controls (36.5±2.9 µm) (P=0.023), although this effect lost statistical significance after application of the Bonferroni correction for multiple comparisons. Both markers of glycemic variability, the AUC for hypoglycemia (R=-0.458, P=0.006) and LGBI (R=-0.473, P=0.004), were negatively correlated with inner temporal INL thickness.ConclusionsPatients with T1DM and no to moderate DR exhibit alterations in inner retinal structure and function. Increased glycemic variability correlates with retinal thinning on OCT imaging, suggesting that fluctuations in blood glucose may contribute to neurodegeneration.

In vitro validation of effects of BDNF-expressing mesenchymal stem cells on neurodegeneration in primary cultured neurons of APP/PS1 mice.

Alzheimer's disease (AD), the most common type of dementia, is characterized by the presence of senile plaques, neurofibrillary tangles, and neuronal loss in defined regions of the brain including the hippocampus and cortex. Transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) offers a safe and potentially effective tool for treating neurodegenerative disorders. However, the therapeutic effects of BM-MSCs on AD pathology remain unclear and their mechanisms at cellular and molecular levels still need to be addressed. In this study, we developed a unique neuronal culture made from 5xFAD mouse, an APP/PS1 transgenic mouse model (FAD neurons) to investigate progressive neurodegeneration associated with AD pathology and efficacy of brain-derived neurotrophic factor expressing-MSCs (BDNF-MSCs). Analyses of the expression of brain-derived neurotrophic factor (BDNF), synaptic markers and survival/apoptotic signals indicate that pathological features of cultured neurons made from these mice accurately mimic AD pathology, suggesting that our protocol provided a valid in vitro model of AD. We also demonstrated amelioration of AD pathology by MSCs in vitro when these FAD neurons were co-cultured with MSCs, a paradigm that mimics the in vivo environment of post-transplantation of MSCs into damaged regions of brains. To overcome failed delivery of BDNF to the brain and to enhance MSCs releasing BDNF effect, we created BDNF-MSCs and found that MSCs protection was enhanced by BDNF-MSCs. This protection was abolished by BDNF-blocking peptides, suggesting that BDNF supply from BDNF-MSCs was enough to prevent AD pathology.

Bone-marrow-derived mesenchymal stem cells attenuate cognitive deficits in an endothelin-1 rat model of stroke.

PURPOSE: Stroke is the third leading cause of death and permanent disability in the United States, often producing long-term cognitive impairments, which are not easily recapitulated in animal models. The goals of this study were to assess whether: (1) the endothelin-1 (ET-1) model of chronic stroke produced discernable cognitive deficits; (2) a spatial operant reversal task (SORT) would accurately measure memory deficits in this model; and (3) bone-marrow-derived mesenchymal stem cells (BMMSCs) could reduce any observed deficits. METHODS: Rats were given unilateral intracerebral injections of vehicle or ET-1, a stroke-inducing agent, near the middle cerebral artery. Seven days later, they were given intrastriatal injections of BMMSCs or vehicle, near the ischemic penumbra. The cognitive abilities of the rats were assessed on a novel SORT, which was designed to efficiently distinguish cognitive deficits from potential motoric confounds. RESULTS: Rats given ET-1 had significantly more cognitive errors at six weeks post-stroke on the SORT, and that these deficits were attenuated by BMMSC transplants. CONCLUSIONS: These findings indicate that: (1) the ET-1 model produces chronic cognitive deficits; (2) the SORT efficiently measures cognitive deficits that are not confounded by motoric impairment; and (3) BMMSCs may be a viable treatment for stroke-induced cognitive dysfunction.

Assessing the potential clinical utility of transplantations of neural and mesenchymal stem cells for treating neurodegenerative diseases.

Treatments for neurodegenerative diseases have little impact on the long-term patient health. However, cellular transplants of neuroblasts derived from the aborted embryonic brain tissue in animal models of neurodegenerative disorders and in patients have demonstrated survival and functionality in the brain. However, ethical and functional problems due to the use of this fetal tissue stopped most of the clinical trials. Therefore, new cell sources were needed, and scientists focused on neural (NSCs) and mesenchymal stem cells (MSCs). When transplanted in the brain of animals with Parkinson's or Huntington's disease, NSCs and MSCs were able to induce partial functional recovery by promoting neuroprotection and immunomodulation. MSCs are more readily accessible than NSCs due to sources such as the bone marrow. However, MSCs are not capable of differentiating into neurons in vivo where NSCs are. Thus, transplantation of NSCs and MSCs is interesting for brain regenerative medicine. In this chapter, we detail the methods for NSCs and MSCs isolation as well as the transplantation procedures used to treat rodent models of neurodegenerative damage.

Obliquity-paced Pliocene West Antarctic ice sheet oscillations.

Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch ( approximately 5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, approximately 40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to approximately 3 degrees C warmer than today and atmospheric CO(2) concentration was as high as approximately 400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO(2).

Effects of TC-1734 (AZD3480), a selective neuronal nicotinic receptor agonist, on cognitive performance and the EEG of young healthy male volunteers.

OBJECTIVES: The aim of this study was to get insight into the central effects of TC-1734 (renamed AZD3480), a selective agonist at the neuronal nicotinic receptor of the alpha4beta2 subtype. MATERIALS AND METHODS: Electroencephalography (EEG) techniques and computerized cognitive tests were performed in young, healthy male volunteers during two double-blind and placebo-controlled studies: a rising single dose crossover study (from 2 to 320 mg) and a rising repeated dose study with a parallel group design (50, 100, and 200 mg). RESULTS: In contrast to acute administration, administration of AZD3480 over 10 days produced statistically significant enhancement of several cognitive measures (attention and episodic memory) compared to placebo. Regarding EEG data, AZD3480 showed acceleration of the alpha centroid and of the alpha peak in the single-dose study. This EEG profile of the acceleration type was confirmed in the repeated dose study on both day 1 and day 10, with the greatest effect observed with the highest dose. The EEG pattern shown for AZD3480 was consistent with that previously described with other drugs known to improve attention and vigilance (including nicotine). In addition, subjects dosed with AZD3480 showed a statistically significant increase in mismatch negativity (MMN) amplitude at 50 and 200 mg while reducing MMN latency (200 mg only), suggesting an improvement of pre-attentional mechanisms. CONCLUSION: These early data in healthy subjects provide encouragement to consider development of AZD3480 as a novel agent for the treatment of cognitive decline in the elderly, including age-associated memory impairment and/or dementia of the Alzheimer's type.

Pharmacokinetics and safety profile of ispronicline (TC-1734), a new brain nicotinic receptor partial agonist, in young healthy male volunteers.

Recent research suggests that drugs activating nicotine acetylcholine receptors might be promising therapy in cognitive decline seen in the elderly, including Alzheimer's disease. Ispronicline (TC-1734), a brain-selective alpha4beta2 nicotine acetylcholine receptor partial agonist, has shown memory-enhancing properties in rodents and a good tolerability profile. The safety and the full pharmacokinetic profile of TC-1734 and its N-desalkylated metabolite, TC-1784, were investigated in 2 phase I studies, and results are reported in this article. Study A used a double-blind, placebo-controlled, crossover design with a rising single-dose scheme (2-320 mg). Study B used a double-blind, placebo-controlled, parallel-group design with a rising multiple-dose scheme (doses: 50, 100, and 200 mg, once daily, x 10 days). Cmax of TC-1734 was reached around 1 to 2 hours postdose, and mean terminal half-life (t1/2) ranged from 3 to 5.3 hours (single doses) and from 2.7 to 8.8 hours (repeated doses). No accumulation of TC-1734 was observed after 10 days. Renal clearance appeared to be a minor method of elimination of TC-1734 and TC-1784. A high interindividual variability was noted for all parameters. Across the dose ranges explored, TC-1734 was safe and well tolerated. No changes of clinical significance were seen on laboratory and cardiovascular parameters. Adverse events were generally of mild to moderate intensity, with dizziness and headache being reported most frequently.

NR2B selective NMDA receptor antagonist CP-101,606 prevents levodopa-induced motor response alterations in hemi-parkinsonian rats.

Sensitization of NMDA receptors containing the NR2B subunit has been increasingly associated with various forms of synaptic plasticity, including those implicated in the pathogenesis of extrapyramidal motor dysfunction. To determine whether activation of NR2B containing receptors contributes to the development and maintenance of levodopa-induced response changes in parkinsonian animals, we evaluated the effects of the selective NR2B antagonist CP-101,606 on these response alterations in unilateral 6-hydroxydopamine (6-OHDA) lesioned rats. Three weeks of twice-daily levodopa treatment decreased the duration of the rotational response to acute levodopa challenge. The response alteration was associated with an increase in GluR1 (S831) phosphorylation in medium spiny neurons of the dorsolateral striatum. Both the attenuated rotational response and augmented GluR1 phosphorylation were decreased by CP-101,606 treatment. These CP-101,606 effects were observed when the compound was administered either at the end of chronic levodopa treatment (ameliorative effect) or together with the twice-daily levodopa treatment for 3 weeks (preventive effect). Furthermore, concurrent administration of CP-101,606 with levodopa potentiated the ability of levodopa challenge to reverse the 6-OHDA lesion-induced contralateral forelimb movement deficit as measured in a drag test. These results suggest that activation of NR2B subunit containing NMDA receptors contributes to both the development and maintenance of levodopa-induced motor response alterations, through a mechanism that involves an increase in GluR1 phosphorylation in striatal spiny neurons.

Children's attentional skills and road behavior.

Switching attention and concentration, 2 skills expected to be used by skillful pedestrians, were studied. A sample of 160 children (aged 4 years 3 months-10 years) played a computer game involving attention switching. To examine concentration, a subset of the children was distracted with a cartoon video while they attempted a difficult task that required matching familiar figures. The same subset was also observed crossing roads. Older children switched faster and were less distracted. Children who were better at switching were more likely to show awareness of traffic when about to cross a road. Children who maintained concentration when challenged by a distracting event crossed the road in a less reckless manner. Parents and educators designing safety programs should take into account the development of these skills.

Orbitally induced oscillations in the East Antarctic ice sheet at the Oligocene/Miocene boundary.

Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3-4 degrees C warmer than at present and atmospheric CO2 concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross Sea that exhibit well dated cyclic variations, and which link the extent of the East Antarctic ice sheet directly to orbital cycles during the Oligocene/Miocene transition (24.1-23.7 Myr ago). Three rapidly deposited glacimarine sequences are constrained to a period of less than 450 kyr by our age model, suggesting that orbital influences at the frequencies of obliquity (40 kyr) and eccentricity (125 kyr) controlled the oscillations of the ice margin at that time. An erosional hiatus covering 250 kyr provides direct evidence for a major episode of global cooling and ice-sheet expansion about 23.7 Myr ago, which had previously been inferred from oxygen isotope data (Mi1 event).

Creatine reduces 3-nitropropionic-acid-induced cognitive and motor abnormalities in rats.

This study assessed whether creatine could attenuate 3-nitropropionic acid (3NP)-induced neuropathological and behavioral abnormalities that are analogous to those observed in Huntington's disease (HD). Rats were fed diets containing either 1% creatine or normal rat chow for 2 weeks prior to the onset of 3NP administration, and for the duration of the study. 3NP was administered systemically in gradually increasing concentrations over an 8-week testing period. Results show that creatine can attenuate 3NP-induced striatal lesions, striatal atrophy, ventricular enlargement, cognitive deficits, and motor abnormalities on a balance beam task. Collectively, these findings indicate that creatine provides significant protection against 3NP-induced behavioral and neuropathological abnormalities and may have therapeutic potential for HD.

Quinolinic acid released from polymeric brain implants causes behavioral and neuroanatomical alterations in a rodent model of Huntington's disease.

Quinolinic acid (QA) is an N-methyl-d-aspartate agonist that has been shown to produce neurotoxic effects that mimic certain neurodegenerative diseases when administered to laboratory animals. Intrastriatal injections of QA in rats have been used extensively to produce some of the neuropathological and behavioral deficits that are analogous to Huntington's disease (HD). However, acute intrastriatal injections of QA produce symptoms that are not analogous to the progressive nature of HD. Thus far, models using chronic administration of QA that produce HD-like behavioral and neuroanatomical changes have necessitated the use of a relatively bulky and fragile microdialytic pump apparatus. The present study tested an alternative way of chronically administering QA. Specifically, this study tested whether gradual release of QA from ethylene vinylacetate (EVA) polymers could produce symptoms analogous to HD. Rats received either no implants or bilateral intrastriatal implants of polymers with or without QA. Subsequent tests for spontaneous motor activity (SMA), grip strength, balance, and learning ability in a radial-arm-water-maze task revealed QA-induced impairments in balance and learning ability, but did not affect grip strength or SMA. Histological analysis revealed QA-induced enlargement of lateral ventricles, striatal atrophy, and striatal neuronal loss, with relative sparing of NADPH-diaphorase-positive neurons. These results suggest that QA released from polymers can produce behavioral and neuropathological profiles analogous to early stages of HD and that EVA polymers offer a useful means of chronically delivering QA in rodent models of neurodegeneration.

Comparison of intrastriatal injections of quinolinic acid and 3-nitropropionic acid for use in animal models of Huntington's disease.

1. The present study compared the effects of acute intrastriatal administration of quinolinic acid (QA) and 3-nitropropionic acid (3-NP), two neurotoxins used in animal models of Huntington's disease (HD), on the following behavioral and histological measures: (1) open field activity levels; (2) performance on balance beam and grip strength tasks; (3) acquisition of a radial-arm-water-maze (RAWM) task; (4) size of striatum and lateral ventricles; (5) amount of cytochrome oxidase (CYO) labeling; and (6) counts of Nissl-stained neurons and NADPH-diaphorase-labeled neurons in the striatum. 2. Rats were given bilateral intrastriatal injections of either 200 nmol QA, 750 nmol 3-NP, or phosphate buffered saline (PBS) two weeks prior to behavioral testing and four weeks prior to histological processing. 3. The behavioral results indicated that both QA and 3-NP injections caused an increase in activity levels at two weeks postlesion, but only the QA rats showed hyperactivity at four weeks postlesion. Both QA and 3-NP rats showed significant impairment in the balance beam task, but only 3-NP rats differed significantly on the grip-strength task. Both toxins caused learning impairments in the RAWM task, with 3-NP rats being more severely impaired. 4. The neuroanatomical results indicated that both QA and 3-NP produced significant striatal atrophy and ventricular dilation, as well as a reduction in CYO staining and loss of Nissl-stained neurons, but only the 3-NP lesions created necrotic cavities in the striatum. However, the QA treatments resulted in significant loss of NADPH-diaphorase neurons in regions peripheral to the site of injection. 5. In general, these results suggest that QA treatments produce milder behavioral and neuroanatomical effects that mimic some of the earlier symptoms of HD, while 3-NP produced more severe effects which mimic both the later symptoms and the juvenile onset of HD.

Small drug sample fabrication of controlled release polymers using the microextrusion method.

Ethylene vinylacetate polymer (EVA) has been used for many years to fabricate controlled-release polymeric implant devices with which drugs of high or low molecular weight compounds could be delivered with zero-order kinetics. However, because the known fabrication methods such as solvent evaporation, casting and possible shrinkage are not sufficiently controllable we have now developed the microextrusion method with which even small amount of clinically important and expensive drugs can be incorporated into EVA with high reproducibility. We show here that devices produced by the microextrusion method allows for a controlled delivery of several neurotoxic and neurotherapeutic compounds such as alpha-methyl-p-tyrosine, diazepam, quinolinic acid, and phencyclidine. Each substance is slowly released from the polymer, as evidenced by spectrophotometric data, for up to 120 days at daily rates varying from 18.4 microg of phencyclidine to 97.6 microg/day of diazepam. Thus, microextrusion is a valuable method for fabricating controlled-release polymers in which small amounts of scarce drugs can be incorporated. Another advantage of the current procedure is that polymers can be fabricated with very little amount of solvent.

Chronic administration of quinolinic acid in the rat striatum causes spatial learning deficits in a radial arm water maze task.

Chronic intrastriatal administration of quinolinic acid (QA) in the rat produces a pattern of neurodegeneration similar to that seen in Huntington's disease (HD). Although these changes have been related to transient motor abnormalities, the effects of chronic QA administration on cognitive abilities have not been assessed. The present study investigated whether the striatal deterioration observed during chronic QA administration produces cognitive impairments in this animal model of HD by testing the effects of chronic administration of QA on spatial learning ability of rats in a radial arm water maze (RAWM) task. Rats were given bilateral implantation of a chronic dialysis probe apparatus which delivered either vehicle or QA (20 mM) into the striatum. Beginning 1 day after implantation, the rats were tested daily for 3 weeks in the RAWM. Nocturnal activity levels were also assessed at 1-, 3-, 5-, 7-, 14-, and 21-days following probe implantation. Results of behavioral testing indicated that chronic exposure to QA causes spatial learning deficits in the RAWM task with only a transient increase in activity levels. Collectively, these results suggest that chronic striatal exposure to QA mimics some aspects of the cognitive deficits observed in HD.