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Effects of oligonucleotide antisense to dopamine D(1A) receptor messenger RNA in a rodent model of levodopa-induced dyskinesia.

Dyskinesias are abnormal involuntary movements which develop as a side-effect of long-term treatment with levodopa in patients with Parkinson's disease. The pathophysiology underlying these dyskinesias remains unclear, although, it has been suggested that heightened activity of dopamine D(1) receptor-bearing striatonigral neurons may play a key role. Chronic pulsatile levodopa administration to hemiparkinsonian rats results in sensitization of rotational responses to apomorphine. This sensitization is thought to be analogous to levodopa-induced dyskinesias in humans. In these studies, we further clarify the role of the dopamine D(1A) receptor in this rodent model of levodopa-induced dyskinesias using an in vivo oligonucleotide antisense approach. Hemiparkinsonian rats received twice daily injections of levodopa for three weeks followed by intrastriatal infusion of dopamine D(1A) receptor antisense (7nmol/day, three days), a scrambled missense control sequence, or saline. Those animals treated with antisense displayed significantly fewer apomorphine-induced rotations than saline- or missense-treated controls.By reducing dopamine D(1A) receptor expression, we were able to attenuate sensitization of the response to apomorphine resulting from chronic pulsatile levodopa treatment. Thus, the dopamine D(1A) receptor appears to play a significant role in levodopa-induced dyskinesias and warrants further examination. These findings may have important implications for the development of selective treatment strategies designed to alleviate parkinsonian symptoms, while minimizing motor complications.

Animals↗

Nucleotide sequence and expression of rat beta-defensin-1: its significance in diabetic rodent models.

beta-Defensins are epithelium-derived antimicrobial peptides that function in the host's innate defense. We identified the first member of the rat beta-defensin family, beta-defensin-1 (BD-1), in the kidney and determined its nucleotide sequence. It was predicted to be a 37-amino-acid peptide. Rat BD-1 mRNA was expressed most abundantly in the kidney, next in skin, tongue, esophagus, and uterus, followed (at low levels) by brain, trachea, stomach, urinary bladder, and ovary. BD-1 gene expression in rat kidney was not increased by lipopolysaccharide administration. BD-1 gene expressions in the kidneys of diabetic rodent models, cholecystokinin-insensitive Otsuka Long-Evans Tokushima Fatty rats, leptin-insensitive obese (fa/fa) Wistar rats, and db/db mice, were significantly lower than those of their lean littermates. BD-1 reduction may be in part responsible for the high incidence of urinary tract infections in diabetes mellitus.

Amino Acid Sequence↗

LY503430, a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor potentiator with functional, neuroprotective and neurotrophic effects in rodent models of Parkinson's disease.

Glutamate is the major excitatory transmitter in the brain. Recent developments in the molecular biology and pharmacology of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) subtype of glutamate receptors have led to the discovery of selective, potent, and systemically active AMPA receptor potentiators. These molecules enhance synaptic transmission and play important roles in plasticity and cognitive processes. In the present study, we first characterized a novel AMPA receptor potentiator, (R)-4'-[1-fluoro-1-methyl-2-(propane-2-sulfonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430), on recombinant human GLUA1-4 and native preparations in vitro and then evaluated the potential neuroprotective effects of the molecule in rodent models of Parkinson's disease. Results indicated that submicromolar concentrations of LY503430 selectively enhanced glutamate-induced calcium influx into human embryonic kidney 293 cells transfected with human GLUA1, GLUA2, GLUA3, or GLUA4 AMPA receptors. The molecule also potentiated AMPA-mediated responses in native cortical, hippocampal, and substantia nigra neurons. We also report here that LY503430 provided dose-dependent functional and histological protection in animal models of Parkinson's disease. The neurotoxicity after unilateral infusion of 6-hydroxydopamine into either the substantia nigra or the striatum of rats and that after systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice were reduced. Interestingly, LY503430 also had neurotrophic actions on functional and histological outcomes when treatment was delayed until well after (6 or 14 days) the lesion was established. LY503430 also produced some increase in brain-derived neurotrophic factor in the substantia nigra and a dose-dependent increases in growth associated protein-43 (GAP-43) expression in the striatum. Therefore, we propose that AMPA receptor potentiators offer the potential of a new disease modifying therapy for Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Effects of folic acid and lamotrigine therapy in some rodent models of epilepsy and behaviour.

It has been suggested that a folic acid (FA) deficiency induced by antiepileptic drugs might be the basis for the neuropsychiatric toxicity associated with these drugs. In the present study, lamotrigine (LTG), one of the newer antiepileptic drugs, was evaluated for its effect on epilepsy, mood and memory in mice. Further, the effect of the addition of FA to LTG therapy was also investigated. The increasing current electroshock seizure test was used to evaluate the anticonvulsant effect of drugs, while the forced swimming test (FST) and spontaneous alternation behaviour (SAB) models were employed for assessing the effects on mood and memory, respectively. LTG exhibited a dose-dependent increase in seizure threshold, whereas FA did not have any effect. LTG did not affect, whereas FA decreased, behavioural depression in the FST in mice. Neither LTG nor FA affected memory scores in the SAB test. The combination of LTG and FA significantly reduced depression while enhancing the effects on memory and seizure threshold. The present observations have confirmed the antiepileptic action of LTG in yet another rodent model of epilepsy. Further, the results clearly demonstrate the additional benefits on epilepsy, mood and memory brought about by the inclusion of FA in the LTG regimen.

Animals↗

Depletion of mitochondrial DNA and enzyme in estrogen-induced hamster kidney tumors: a rodent model of hormonal carcinogenesis.

Mitochondrial DNA (mtDNA) encodes for 13 polypeptides critical for normal functioning of the electron transport chain and damage to mtDNA has been associated with aging, and implicated in several disease processes. Although damage to mtDNA is being implicated in mutagenesis and carcinogenesis, there are limited studies demonstrating the role and extent of mtDNA damage in human or rodent cancers. Using serial dilution and competitive polymerase chain reaction analysis, we have quantitated the amount of total mtDNA and analyzed the extent of mtDNA damage in estrogen-induced and estrogen-dependent hamster kidney tumors. The hamster kidney tumor model is a useful and widely investigated rodent model of hormonal carcinogenesis, which shares several characteristics with human breast and uterine cancers, and point to a common mechanistic pathway. Our data indicate a significant decrease in the copy number of total mtDNA and the activity of a nuclear-encoded mitochondrial enzyme citrate synthase in hamster kidney tumors compared to age-matched controls. Since there are several hundred mitochondria in a cell and each mitochondrion has multiple copies of mtDNA, a very small percentage of somatic deletion mutation may not be enough to result in a decreased capacity of the mitochondrial genome. However, a significant increase in deletion mutations or a decrease in the mtDNA copy number can result in a decreased oxidative phosphorylation capacity of the mitochondria and decreased energetics, and thus increased susceptibility to the disease process. Therefore, estrogen-induced hamster kidney tumor model can be a useful rodent model of carcinogenesis to understand the role of mtDNA damage in cancer progression and development.

Animals↗

Changes in the immune system in rodent models of depression.

This review summarizes some of the evidence which implicates an increase in the peripheral and central secretion of pro-inflammatory cytokines in the behavioural changes seen in some stress-induced and brain lesion models of depression. Following a consideration of the role of cytokines in the periphery and the brain, evidence is presented suggesting that pro-inflammatory cytokines alter the function of monoamine neurotransmitters which have been implicated in severe stress and in major depression. These changes occur in the presence of elevated glucocorticoid concentrations which suggests that immune activation is correlated with a decrease in the sensitivity of the glucocorticoid receptors on immune cells in addition to those occurring in the brain. The review concludes with a brief account of the various rodent models of depression in which evidence of immune activation as been demonstrated.

Amnesia↗

The effect of ketotifen in rodent models of anxiety and on the behavioural consequences of withdrawing from treatment with drugs of abuse.

Ketotifen was compared to diazepam to inhibit aversive responding of the mouse in a black and white test box and in the rat social interaction test. Both drugs reduced aversive responding in the mouse to the brightly illuminated area of the test box and facilitated social interaction in the rat; ketotifen was approximately 100 times more potent than diazepam. The chronic administration of diazepam, ethanol, nicotine and cocaine in the mouse also reduced aversive responding but their withdrawal was associated with an increased behavioural suppression. The administration of ketotifen during the period of withdrawal from diazepam, ethanol, nicotine and cocaine prevented the exacerbation in aversive responding. It is concluded that ketotifen, like diazepam and 5-HT3 receptor antagonists, can reduce behavioural suppression in rodent models of anxiety and attenuate the behavioural consequences of withdrawal from treatment with drugs of abuse.

Animals↗

A rodent model for investigating the neurobiology of contralateral neglect.

BACKGROUND: Contralateral neglect is a common and disabling sequela of right hemisphere strokes. Neglect involves attentional and cognitive deficits, including distortions of contralateral spatial and personal awareness. There are no established successful therapies for neglect, and treatment is often complicated by anosognosia. The disturbances associated with neglect are debilitating to patients and their families, and presence of neglect is a strong predictor of poor prognosis for recovery. OBJECTIVE: The present report reviews findings from 20 years of research using a rat model of neglect. In the rat, 2 cortical areas that are linked by corticocortical connections have been identified as having a major role in neglect, and these correspond to frontal and parietal fields in primates. These 2 cortical areas also have convergent projections to the dorsocentral striatum, which has been implicated as a crucial subcortical component of the cortical-striatal-thalamic circuitry involved in directed attention and neglect. We discuss the role of the dorsocentral striatum in neglect and recovery and present evidence that induced axonal sprouting may promote functional recovery following cortical lesions that produce neglect. CONCLUSIONS: The rodent model of neglect captures some of the essential behavioral and anatomic features of neglect in humans. This model has helped reveal the pathophysiology of neglect, has suggested a crucial role of the striatum in recovery from neglect, and is being used to investigate potential therapeutic approaches.

Agnosia↗

Capucin: a novel striatal marker down-regulated in rodent models of Huntington disease.

In an initial study, we compared quantitative transcriptome data across mouse brain territories using the serial analysis of gene expression method. Among the novel regional markers that we discovered, we focused on a striatum-enriched transcript with no available experimental cDNA sequence. Here, we report its cloning, gene structure, and detailed distribution in mouse brain. Quantitative RT-PCR and in situ hybridization demonstrated predominant expression in dorsolateral striatum. We therefore named it capucin for caudate-and putamen-enriched sequence. Mouse capucin is a 237-amino-acid protein, without any registered ortholog in mammalian species. It contains no recognizable motif other than two predicted carboxy-terminal transmembrane domains. When expressed in fusion with a fluorescent protein, it localized to the Golgi apparatus in two mammalian cell lines. Interestingly, we observed a significant down-regulation of capucin mRNA levels in two rodent models of Huntington disease, indicating a possible contribution to the pathogenesis of this disorder.

Amino Acid Sequence↗

Biochemical and behavioral recovery in a rodent model of Parkinson's disease following stereotactic implantation of dopamine-containing liposomes.

We have developed and characterized dopamine-containing liposomes which exhibited in vitro sustained release of dopamine for over 40 days. These liposomes were stereotactically implanted into the partially denervated corpus striatum of rats subjected to unilateral lesions of the substantia nigra. In vivo release of dopamine into striatal extracellular fluid was monitored by microdialysis and behavior was assessed by quantifying apomorphine-induced asymmetric rotation. Extracellular dopamine levels in the partially denervated striatum of the dopamine liposome-treated rats were greater than the levels in the lesioned rats which received control liposomes and these levels remained elevated for 25 days. In parallel, those rats which received dopamine liposomes exhibited partial behavioral recovery, with attenuation of asymmetric rotation following systemic apomorphine administration. These results suggest that dopamine-containing liposomes can partially ameliorate the deficits associated with a rodent model of Parkinson's disease, and demonstrate the potential of this technology as a method for the controlled delivery of therapeutic agents into discrete areas of the brain.

Animals↗

Pharmacological and pharmacokinetic characterization of the cannabinoid receptor 2 agonist, GW405833, utilizing rodent models of acute and chronic pain, anxiety, ataxia and catalepsy.

To date, two cannabinoid receptors have been identified, CB1 and CB2. Activation of these receptors with non-selective cannabinoid receptor agonists reduces pain sensitivity in animals and humans. However, activation of CB1 receptors is also associated with central side effects, including ataxia and catalepsy. More recently, a role for selective CB2 agonists in pain modification has been demonstrated. GW405833, a selective CB2 agonist, was recently reported to partially reverse the inflammation and hyperalgesia in a rat model of acute inflammation. In the current report, we extend the characterization and therapeutic potential of this compound. For the first time, we show that GW405833 selectively binds both rat and human CB2 receptors with high affinity, where it acts as a partial agonist (approximately 50% reduction of forskolin-mediated cAMP production compared to the full cannabinoid agonist, CP55,940). We also report for the first time that intraperitoneal administration of GW405833 (0.3-100 mg/kg) to rats shows linear, dose-dependent increases in plasma levels and substantial penetration into the central nervous system. In addition, GW405833 (up to 30 mg/kg) elicits potent and efficacious antihyperalgesic effects in rodent models of neuropathic, incisional and chronic inflammatory pain, the first description of this compound in these models. In contrast, analgesia, sedation and catalepsy were not observed in this dose range, but were apparent at 100 mg/kg. Additionally, GW405833 was not antihyperalgesic against chronic inflammatory pain in CB2 knockout mice. These data support the tenet that selective CB2 receptor agonists have the potential to treat pain without eliciting the centrally-mediated side effects associated with non-selective cannabinoid agonists, and highlight the utility of GW405833 for the investigation of CB2 physiology.

Amines↗

Peripheral inflammation and neuroprotection: systemic pretreatment with complete Freund's adjuvant reduces 6-hydroxydopamine toxicity in a rodent model of Parkinson's disease.

Complete Freund's adjuvant (CFA), a pro-inflammatory agent, was inoculated, subcutaneously, to Sprague-Dawley rats prior to the intrastriatal injection of 6-hydroxydopamine (6-OHDA). Animals were sacrificed 7 and 28 days following 6-OHDA injection; neuronal damage, glial activation and cytokine levels, within the nigrostriatal system, were then investigated. Nigrostriatal degeneration induced by 6-OHDA was accompanied by early microglial and astroglial activation, which preceded the onset of dopaminergic cell loss, in the SNc, without significant changes in cytokine levels. CFA pretreatment markedly reduced the SNc neuronal loss and associated microglial activation, as well as the rotational response to apomorphine. These changes were associated with moderate, transient increases in the nigrostriatal levels of glial-cell-derived neurotrophic factor (GDNF) and pro-inflammatory cytokines, including interleukin (IL)-1alpha, IL-1beta and IL-6. Our results show that prior delivery of a peripheral, pro-inflammatory stimulus induces neuroprotection, in a rodent model of Parkinson's disease, possibly through the modulation of cytokine production at the nigrostriatal level.

Adjuvants, Immunologic↗

Neurotrophic enhancers as therapy for behavioral deficits in rodent models of Huntington's disease: use of gangliosides, substituted pyrimidines, and mesenchymal stem cells.

The interest in using neurotrophic factors as potential treatments for neurodegenerative disorders, such as Huntington's disease, has grown in the past decade. A major impediment for the clinical utility of neurotrophic factors is their inability to cross the blood-brain barrier in therapeutically significant amounts. Although several novel mechanisms for delivering exogenous neurotrophins to the brain have been developed, most of them involve invasive procedures or present significant risks. One approach to circumventing these problems is using therapeutic agents that can be administered systemically and have the ability to enhance the activity of neurotrophic factors. This review highlights the use of gangliosides, substituted pyrimidines, and mesenchymal stem cells as neurotrophic enhancers that have significant therapeutic potential while avoiding the pitfalls of delivering exogenous neurotrophic factors through the blood-brain barrier. The review focuses on the potential of these neurotrophic enhancers for treating the behavioral deficits in rodent models of Huntington's disease.

Animals↗

Development and characterization of a rodent model of methanol-induced retinal and optic nerve toxicity.

Methanol is an important public health and environmental concern because of the selective actions of its neurotoxic metabolite, formic acid, on the retina, optic nerve and central nervous system. Humans and non-human primates are uniquely sensitive to methanol-induced neurotoxicity as a consequence of the limited capacity of primate species to oxidize and thus detoxify formic acid. The toxic syndrome in primates is characterized by formic acidemia, metabolic acidosis and blindness or serious visual impairment. Nonprimate species are normally resistant to the accumulation of formate and associated metabolic and visual toxicity. We have characterized retinal and optic nerve toxicity in a nonprimate model of methanol toxicity using rats in which folate-dependent formate oxidation has been selectively inhibited, allowing formate to accumulate to toxic concentrations following methanol administration. Methanol-intoxicated rats developed formic acidemia, metabolic acidosis and visual toxicity analogous to the human methanol poisoning syndrome. Visual dysfunction was manifested as reductions in the electroretinogram and the flash-evoked cortical potential which occurred coincident with blood formate accumulation. Histological studies revealed mitochondrial disruption and vacuolation in the retinal pigment epithelium, photoreceptor inner segments and optic nerve. The temporal relationship between methanol administration and the onset and development of ocular toxicity, as well as, the degree of metabolic acidosis and extent of formic acidemia in this rodent model are remarkably similar to that documented in human methanol intoxication. Moreover, the functional and morphologic findings in methanol-intoxicated rats are consistent with the hypothesis that formate acts as a mitochondrial toxin in the retina and optic nerve. The establishment and characterization of this nonprimate animal model of methanol intoxication will facilitate research into the mechanistic aspects of methanol toxicity and the development and testing of treatments for human methanol poisoning.

Animals↗

Central administration of the neurotensin receptor antagonist SR48692 attenuates vacuous chewing movements in a rodent model of tardive dyskinesia.

Tardive dyskinesia is a movement disorder that develops in 20-30% of patients treated with chronic neuroleptics. Whilst the pathogenesis of tardive dyskinesia remains unclear, altered expression of neuropeptides in the basal ganglia has been implicated in its emergence. The peptide neurotensin is expressed in both dopamine D1 receptor-bearing neurons of the direct striatonigral pathway and dopamine D2 receptor-bearing neurons of the indirect striatopallidal pathway. Increased levels of striatal neurotensin messenger RNA (mRNA) are reported following chronic neuroleptic therapy. Chronic treatment with the typical antipsychotic haloperidol elicits neurotensin immunoreactivity in a large number of striatopallidal and a modest number of striatonigral projection neurons, whilst treatment with the potent dopamine releaser, methamphetamine, induces intense neurotensin immunoreactivity in striatonigral projection neurons. In order to determine whether increased levels of striatal neurotensin mRNA in the direct striatonigral or the indirect striatopallidal pathway play a more influential role in the development of tardive dyskinesia, we explored the effects of a specific neurotensin antagonist in a rodent model (vacuous chewing movements [VCMs] induced by chronic neuroleptics). Three groups of animals received injections of fluphenazine decanoate (25 mg/kg) or its vehicle sesame oil every 3 weeks for at least 18 weeks. They were then surgically implanted with bilateral guide cannulae aimed at the striatum, the substantia nigra pars reticulata, or the globus pallidus respectively. After recovery, animals were infused with 2-[(1-(7-chloro-4-quinolinyl)-5-(2,6-imethoxyphenyl)pyrazol-3-yl)carbonylamino]tricyclo(3.3.1.1.(3.7))decan-2-carboxylic acid (SR48692; 0.25, 0.50, and 1.0 nmol/microl), or its vehicle (10% dimethyl sulfoxide [DMSO] in saline) and observed for 60 min. Intra-striatal, intra-nigral or intra-pallidal infusion of SR48692 attenuated neuroleptic-induced VCMs. These findings lend further support to a role for neurotensin in the development of VCMs but do not clarify which pathway plays a more important role. Thus, treatments that reduce or prevent the effects of increased neurotensin expression and release may be useful in the management of tardive dyskinesia.

Animals↗

Opioid peptides endomorphin-1 and endomorphin-2 in the immune system in humans and in a rodent model of inflammation.

Endomorphin (EM)-1 and EM-2 are tetrapeptides with high affinity and selectivity for the micro-opioid receptor. We have utilized specific radioimmunoassays to characterize EM-1 and EM-2 in immune tissues from normal human subjects and from rats with adjuvant arthritis (AA). PBLs from three normal human subjects contained 248, 13, and 303 pg EM-1 per 100 million cells, whereas EM-2 was measured in two subjects at 69 and 588 pg per 100 million cells. In AA rats, EM-1 (but not EM-2) contents in the spleen and thymus were elevated compared with levels in tissues from non-AA controls. EM-1 was detectable in five of eight samples of synovial tissue from inflamed hind paws, whereas EM-2 was detectable in two of eight synovial extracts. Neither EM-1 nor EM-2 were detectable in synovial tissue from non-AA rats. To our knowledge, this is the first report of endomorphins in normal human immune cells. Increased endomorphin expression or uptake in peripheral tissues in a rodent model of chronic inflammation provides potential for endomorphins to selectively modulate chronic inflammation in mammals.

Animals↗

The effect of Roux-en-Y diversion on gastric and Roux-limb emptying in a rodent model.

BACKGROUND: The "Roux stasis syndrome" is characterized by symptoms of upper gut stasis following Roux-en-Y gastrojejunostomy (RG). Whether symptoms result from delayed gastric emptying, altered Roux-limb transit, or both has never been settled, partly because of the difficulty of measuring Roux-limb transit. The aim of this study was to develop a model to simultaneously quantitate Roux-limb transit and gastric emptying. METHODS: Rats underwent vagotomy and antrectomy with RG or Billroth II reconstruction (B-II). Gastrointestinal transit of a solid meal (Technetium-99m sulfur colloid-labelled egg white) was assessed 0.5, 1, and 1.5 hours postprandial (pp). Transit of a liquid marker (Na51-CrO4 injected through an efferent-limb catheter) was measured at 25 minutes pp. RESULTS: Solid gastric emptying was slower in RG than in B-II rats at 60 and 90 minutes pp. More of the solid meal and of the liquid marker was retained in the Roux limb than the efferent limb of the B-II at all time points (P < 0.05). CONCLUSIONS: In a rodent model, Roux-en-Y gastrojejunostomy is associated with delayed gastric emptying and slowed efferent-limb transit of solids and liquids.

Analysis of Variance↗

The experimental chemotherapy of leishmaniasis, VI. The development of rodent models for cutaneous infection with L. major and L. mexicana amazonensis.

Two models have been established of leishmanial infections in random-bred TFW albino mice, one with Leishmania major LV39 and the other with L. mexicana amazonensis LV38. These parasites produce consistent lesions when injected subcutaneously a short distance anterior to the base of the tail. Consistent infections could not be produced in the mice with other lines of the L. mexicana group of skin-dwelling protozoa, nor with a line of L. braziliensis guyanensis (LV475). The development of procedures for the maintenance of these parasites, the routine infection of mice and drug testing are described. L. major inocula consist of 1--5 X 10(6) promastigotes derived from NNN culture. L. m. amazonensis inocula contain approximately 10(7) amastigotes obtained from lesions in hamsters. The effects of drugs on the rodent lesions are assessed by two methods. Method A provides a simple lesion score from 0 to 3 made when lesions in control animals begin to reach maximum development (about six weeks after infection). Method B summates earlier 'mean lesion scores' to provide a graphic analysis of doses giving 50 and 90% lesion suppression at the end of seven weeks after the start of treatment which is for five consecutive days (SD 50 and SD90). The activities of several compounds used for the treatment of human leishmanial infections (organic antimonials, diamidines, amphotericin B and primaquine) are compared in mice infected with L. major LV39, L. m. amazonensis LV78 and 'L. infantum LV9' (the latter as reported earlier). It is concluded that the rodent models provide a good parallel with the response to these compounds in man. The visceral organism is significantly more responsive to Pentostam and Glucantime than are L. major or L. m. amazonensis. Primaquine is active only against 'L. infantum LV9'. All three parasites in mice respond to Berenil, but not to pentamidine which is used in the treatment of kala-azar. Amphotericin B is effective against cutaneous and visceral infections, but precautions must be taken to ensure its absorption by experimental animals.

Animals↗