Glutamate receptor block in Lurcher mutant mice during ontogeny and its effect on hippocampal long-term potentiation.

Basic evaluation of the effect of chronic NMDA glutamate receptor (NMDAR) blockade on the hippocampal long-term potentiation (LTP) was performed in an animal model of inborn olivo-cerebellar degeneration (Lurcher mutant mice, LMM). NMDA receptor antagonist MK-801 was administered to mice in the dose 0.2 mg/kg of body weight, daily during two periods of their ontogeny: D5-D26 and D91-D111. In the consecutive 15 days some behavioral characteristics were studied using special methods for physical activity testing. Then LTP was investigated in LMM and also in their healthy littermates which served as controls (wild-type, WT). LTP in animals pre-treated with MK-801 showed significant long-term suppression of NMDAR activity, in both WT and LMM despite certain small differences between them. Our results show that cerebellar pathology on one hand and a physical activity on the other hand can influence the LTP in hippocampal region. It can be concluded that the results support the ideas of close functional cooperation between the brain structures which are involved in mechanisms of learning and memory.

The effect of D1-like receptor blockade on motor functions and spatial learning in B6CBA mice.

Dopaminergic neurotransmitter system plays a role in many neural functions, for instance in the motor system. Dopamine also influences cognitive functions, motivation and behaviour. In this study, the effect of D1-like receptors blocker SCH 23390 on spontaneous motor activity, motor functions and spatial learning in adult wild type mice derived from the strain B6CBA was investigated. The animals of one group were administered with D1-like receptors blocker SCH 23390 while the mice from the other group were treated with the saline solution 20 minutes before experiments. Spontaneous motor activity was examined in the open field. Motor functions were examined using horizontal wire, ladder and rotarod. Spatial learning was tested in the Morris water maze. D1-like receptors inhibition significantly decreased spontaneous motor activity. In the horizontal wire test, the mice treated with SCH 23390 manifested significantly better results than control animals. No significant differences between experimental animals and controls were found in the ladder test. On the rotarod, the animals with D1-like receptors inhibition reached significantly shorter latencies than the animals treated with the saline solution. D1-like receptors blockade led to significant impairment of performance in experimental animals in the Morris water maze. Spontaneous motor activity and motor skills were influenced by evoked hypokinesia. Meanwhile in the horizontal wire test this effect seemed to be advantageous, in the rotarod test it meant a definite handicap because this test requires good motor coordination and activity. The results gained in the Morris water maze indicated that not only hypokinesia played some role there but also spatial learning and perhaps motivation were affected. The study confirmed that D1-like receptors inhibition has effects on both motor and cognitive functions in mice. However the motor effects are not the main cause of the failing in the spatial learning test.

The time-dependent block of NMDA glutamate receptor influences hippocampal LTP in inborn cerebellar degeneration mouse model.

The effect of single dose of NMDA glutamate receptor blockage administration on the hippocampal LTP was evaluated in animal model of inborn cerebellar degeneration. We compared the level of possible LTP blockade in two groups of animals, Lurcher mutant mice and their healthy littermates which served as controls. In the second part of the study we tested group of mice which were influenced repeatedly by the same NMDA blocker (MK-801) during behavioral experiments. Our results suggest a similar effect of blockade either after single or chronic MK-801 administration; both of them practically disrupted LTP generation with differences between healthy and neurodegenerative animals.

Motor and visuospatial abilities in a model of olivocerebellar and retinal degeneration--Lurcher mutant mice of C3H strain.

Lurcher mutant mice represent a natural model of olivocerebellar degeneration. They suffer from loss of Purkinje cells and decreased number of granule cells and inferior olive neurons. The degeneration leads to cerebellar ataxia and deterioration of cognitive functions. Some animals of the C3H strain have also the retinal degeneration. The aim of the study was to analyze the morphology of cerebellar and retinal degeneration and to evaluate the ability of motor coordination and visuospatial orientation in C3H Lurcher mutant mice. Cerebella of Lurcher mutant and wild type mice were examined with several histological, histochemical and immunohistochemical methods. Motor coordination was tested on a bar, ladder and rotarod. Spatial orientation and learning were tested in the Morris water maze with visible or hidden platform. Histological examinations showed decreased numbers of Purkinje cell in Lurchers. Various histological methods brought different information about the course or stage of the cerebellar degeneration. Retinal degeneration was identified with hematoxyline-eosine staining very well. Lurchers performed worse in motor coordination tests and in both the spatial orientation and learning test. Retinal degeneration influenced negatively both the spatial learning and orientation. Motor tests were influenced by retinal degeneration only in the wild type mice. Wild type mice showed some ability of idiothetic navigation, which was not found in Lurchers.

Preliminary study of the effect of repeated motor training on spatial learning ability in adult lurcher mutant mice.

Lurcher mutant mice represent a model of olivocerebellar degeneration. They suffer from cerebellar ataxia and deterioration of cognitive functions. The aim of the work was to study the effect of repetitive enforced motor training on spatial learning ability and motor coordination in adult Lurcher mutant mice of the C57BI strain. Experimental mice were trained repetitively on a rotarod. Control mice were left without the training. Motor coordination was tested four times-before the training, in the third week of the training, at the end of the training and after a spatial learning test following the training. A rotarod of higher cylinder diameter and lower rotation speed was used. Spatial learning was examined using the Morris water maze. Trained animals achieved significantly better results than untrained mice in the 2nd and 3rd motor coordination test. In the last test following the spatial learning examination, untrained mice improved their performances so that there were no differences between trained and untrained group. In the Morris water maze trained mice showed higher spatial learning ability than untrained animals. Motor coordination capability of adult Lurcher mutant mice was improved by the training on rotarod but also by swimming during the experiment in the water maze. Repetitive motor activity led to increase of spatial learning ability.

Changes of dopamine receptors in mice with olivocerebellar degeneration.

Lurcher mutants are mice with functional mutation in the 82 glutamate receptor (GluRdelta2) that is predominantly expressed in cerebellar Purkinje cells and plays a crucial role in cerebellar functions. These mice display ataxia and impaired motor-related learning tasks. In order to elucidate the role of dopaminergic receptor system in coping with mutation in delta2 glutamate receptor the behavioral effect (spatial learning) of D1 dopamine receptor activation and inhibition and changes in D1-like and D2-like dopamine receptors in striatum, hippocampus and cerebellum in C57BI/7 and C3H Lurcher mutants and wild type mice were studied. We have found that Lurcher mutants were worse in the spatial learning but mice of both types reacted similarly to D1 dopamine receptor agonist (without effect) and antagonist (worsening). Moreover, Lurchers revealed substantial higher density of both D1-like and D2-like dopamine receptors in hippocampus in C57BI/7 strain, while in C3H strain only D1-like dopamine receptors were higher. In C57BI/7 strain, D-like dopamine receptors were lower in cerebellum; D2-like dopamine receptors were not affected. In the striatum, the receptor densities were similar to the wild type counterparts. Our results suggest specific participation of dopamine receptor system in coping with olivocerebellar degeneration.

Does transplantation of cerebellar embryonic tissue influence hippocampal LTP in adult Lurcher mutant mice?

Possible influence of embryonic cerebellar graft transplanted into the adult neurodegenerative brain in Lurcher mutant mice on long-term potentiation (LTP) in hippocampus was investigated. Evaluation of LTP ability and comparison with the tests of motor learning suggests similarities between magnitude of LTP and criteria of motor learning. Also interstrain differences were described. Our results support ideas about tight cooperation among brain structures which are involved in mechanisms of learning and memory.

Comparison of embryonic cerebellar graft survival in adult Lurcher mutant mice of strains C3H and C57Bl/7.

Lurcher mutant mice suffer from complete loss of cerebellar Purkinje cells. The aim of the work was to compare the solid embryonic cerebellar graft survival in adult Lurcher mutant mice derived from strains C3H and C57Bl/7 and to assess the morphology of the grafts. Embryonic cerebellar tissue was obtained from 12-13 days mice embryos expressing green fluorescent protein (GFP). Embryonic cerebellum was injected with a glass microcapillary into the cerebellum of adult Lurcher mutant mouse. Host mice were sacrificed 2-12 weeks after the transplantation. Brainstems and cerebella were examined histologically. The graft and graft derived GFP-positive cells were detected according to their green fluorescence. To visualise the structure of the graft Nissl staining was used. Graft survival percentage was evaluated in groups of mice sacrificed during the first, second or third month after the transplantation. The graft was found in all C57Bl/7 mice and in 90.9% of C3H mice examined within one month after the transplantation. In the second month the graft was present in 83.3% of C57Bl/7 and 50.0% of C3H mice. Till the third month the graft survived in 68.2% of C57Bl/7 mice and 22.2% of C3H mice. In C57Bl/7 mice a cerebellar structure was developed in the graft and migration of graft derived-cells to the host tissue was observed more often than in C3H mice. C567Bl/7 mice seem to be more suitable for experiments testing functional consequences of transplantation into the cerebellum requiring good long-term graft survival.

Various methods of Purkinje cells transplantation and their functional response in Lurcher mutant mice.

Embryonic cerebellum was transplanted to adult Lurcher mutant mice affected with hereditary olivocerebellar degeneration and with resulting cerebellar ataxia. Grafts were applied as solid pieces of tissue or as cell suspensions. The aim was to replace Purkinje cells lost by the neurodegeneration with embryonic cells and to observe the effect on motor symptoms of cerebellar ataxia. Success rate of the two methods was also compared. Motor skills were tested before and in week intervals after the transplantation. The results were compared with sham-operated controls. When the solid graft was transplanted, the success rate was two times higher as compared with the cell suspension method. Fibre sprouting and cell migration from the graft to the host tissue was observed. Insignificant amelioration of motor skills was found in mice after the solid cerebellar tissue transplantation, while the cell suspension application had no effect.

Functional consequences of retinal degeneration in spatial orientation in C3H wild type and Lurcher mutant mice.

Lurcher mutant mice represent a model of genetically determined olivocerebellar degeneration. In the C3H strain there is also hereditary retinal degeneration. The aim of this work was to assess, whether the retinal degeneration influences spatial orientation and results of the spatial learning tasks. Two experiments in the Morris water maze were arranged. First, mice learned to find a platform position, which was linked to two labels on the periphery of the maze. In the second experiment the platform was removed and swimming velocity and preference of central or peripheral zone of the maze were assessed. Presence of the retinal degeneration was detected histologically. Both Lurcher mutant and wild type mice that exhibited long latencies in the first experiment were affected with the retinal degeneration, while animals that performed the trial well, had normal retina. Swimming velocity was not changed substantially. The maze exploration strategy was different in mice with and without the retinal degeneration.