Changes of motor abilities during ontogenetic development in Lurcher mutant mice.

Lurcher mutant mice represent a natural model of olivocerebellar degeneration. This degeneration is caused by a mutation of the gene for the delta2 glutamate receptor. Lurcher mutants suffer from cerebellar ataxia and cognitive functions deficiency as a consequence of excitotoxic apoptosis of Purkinje cells in the cerebellar cortex and a secondary decrease of granule cells and inferior olive neurons. This process finishes by the 90th day of postnatal life, but already by 14 days, the Purkinje cells are damaged and the ataxia is fully developed. Purkinje cells die by apoptosis within the first 3 weeks of life. The aim of our work was to study the development of motor functions in the course of the ontogenetic development in Lurcher mutant mice of the B6CBA strain and to compare it with wild type mice of the same strain. Mice aged 2, 3, 6, 9, and 22 weeks were used in our experiment. Motor skills were examined using four standard tests: the horizontal wire, rotating cylinder, footbridge and slanting ladder. Our findings in Lurcher mutant mice show a significant increase of motor abilities up to the sixth postnatal week and selective decrease early after this period. This improvement of motor skills is caused by the physiological development of musculature and the nervous system, probably with some contribution of plasticity of the maturing brain. The cause of the decline of these abilities immediately after the completion of the development is unknown.

The effect of nitric oxide synthase inhibitors nitro-L-arginine and 7-nitroindazole on spatial learning and motor functions in Lurcher mutant and wild type mice.

Nitric oxide (NO) is an intercellular messenger that, among other things, plays an important role in the nervous system as a gaseous neurotransmitter, modulating long-term potentiation (LTP) induction of synaptic transmission. LTP has been suggested to be the basis of memory formation. On the other hand NO also participates in excitotoxic processes which play an important role in many neuropathological states. The aim of this work was to observe the effect of two NO synthase (NOS) inhibitors (N omega-Nitro-L-arginine, NA; 7-nitroindazole, NI) on spontaneous behaviour, spatial learning and motor functions in Lurcher (+/Lc) and wild type (+/+) mice, derived from the B6CBA strain. Heterozygous Lurcher mutant mice represent a natural model of the olivocerebellar degeneration. They suffer from postnatal, practically total, extinction of cerebellar Purkinje cells (due to the excitotoxic apoptosis) and a partial decrease of granule cells and inferior olive neurons (ION) because of the lost target of their axons. +/+ animals are healthy littermates of +/Lc. NA is a nonselective NOS inhibitor which influences, except neuronal (n), also endothelial (e) NOS with an impact on blood pressure, NI is a selective nNOS inhibitor without any circulatory effect. The adult animals of both types (+/Lc; +/+) were influenced by acute administration of both inhibitors (25 mg/kg i.p. 30 min. before experiments) and newborns only by both acute and long-term administration of NI (1 month, starting from postnatal day 2, P2). Control solutions - saline or solvents of both NA and NI inhibitors--diluted 1M HCl and dimethyl sulfoxide (DMSO) respectively, were given at a relevant volume in the same way. The effect of both inhibitors and control solutions on motor functions was tested using four standard procedures (horizontal wire, slanting ladder, rotating cylinder, foot-bridge); in newborns at the age of 14 days. Spatial learning ability was examined in five-day long procedure in the Morris water maze (MWM) (in newborns started on P21). Spontaneous behaviour was studied only in adult animals (after acutely influencing them) employing the open field method. The results showed, that neither the Lurcher mutant, nor wild type mice derived from the B6CBA strain were significantly affected by NOS inhibitors NA and NI in spatial learning after both the acute and long-term application. Only significant decrease of swimming speed was found in both types of mice after the acute administration of NI and in the wild type animals after the acute administration of NA. Motor functions were significantly negatively affected only in the Lurcher mutants after both the acute and chronic application of NI.

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.

Biological effects of noble gases.

Noble gases are known for their inertness. They do not react chemically with any element at normal temperature and pressure. Through that, some of them are known to be biologically active by their sedative, hypnotic and analgesic properties. Common inhalation anesthetics are characterized by some disadvantages (toxicity, decreased cardiac output, etc). Inhalation of xenon introduces anesthesia and has none of the above disadvantages, hence xenon seems to be the anesthetic gas of the future (with just one disadvantage - its cost). It is known that argon has similar anesthetic properties (under hyperbaric conditions), which is much cheaper and easily accessible. The question is if this could be used in clinical practice, in anesthesia of patients who undergo treatment in the hyperbaric chamber. Xenon was found to be organ-protective. Recent animal experiments indicated that xenon decreases infarction size after ischemic attack on brain or heart. The goal of our study is to check if hyperbaric argon has properties similar to those of xenon.