Involvement of the NO synthase system in stress-mediated brain reactions.

The neurosis-like state developing as a result of chronic stress in animals and accompanied by transient cerebral hypoxia can lead to significant impairments to many brain structures. The effects of the humoral components of the stress reaction on the brain are mediated by both extra- and intracellular signal pathways, among which nitric oxide (NO) is of great importance. We report here immunohistochemical studies of the expression of the constitutive neuronal (nNOS) and inducible (iNOS) isoforms of NO synthase in neurons in the brains of white rats in conditions of chronic stress leading to the development of a neurosis- like state. Chronic stress was found to induce increases in nNOS and iNOS expression in many parts of the brain, predominantly in the neocortex and hippocampus. Administration of the nonspecific NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) (10 mg/kg) led to increases in the animals' depression, which was accompanied by reductions in motor and investigative activity assessed using traditional tests. This NOS inhibitor produced a minor increase in the expression of iNOS only. Thus, NO was shown to be involved in mediating the effects of stress with development of a neurosis-like state.

Studies of damage to hippocampal neurons in inbred mouse lines in models of epilepsy using kainic acid and pilocarpine.

Identification of the mechanisms of damage to neurons is an important task in contemporary neuroscience and is of enormous importance in medicine. This report compares two models of neuron damage due to hyperexcitation induced by kainic acid and pilocarpine, using two lines of mice, C57BL/6J and FVB/NJ. Neuron damage was more marked in FVB mice, though lethality was greater in C57BL mice. The levels of convulsive activity were not significantly different. Kainic acid had greater tropism for the hippocampus than pilocarpine. Hsp-70 and Egr-1 expression was not significantly different in C57BL and FVB mice. Analysis of the isolated mitochondrial fraction showed that free radical production was different in these mouse lines; this may be one of the reasons for the differential resistance of neurons to hyperexcitation.

Nestin-expressing cells in the human hippocampus.

Nestin, a protein of the intermediate filament family, is typical of undifferentiated neural stem and progenitor cells. The present report describes studies of nestin expression in the hippocampus of patients with epilepsy and identifies five types of nestin-immunopositive cells differing in terms of their morphological phenotype and immunological characteristics. These were cells with the phenotype of radial glial cells, bipolar cells, small dendritic cells, cells of the subependymal zone, and astrocyte-like cells. Two types of cell - radial gliocytes of the dentate fascia and NG2-immunopositive bipolar cells - can be regarded as neural precursors of different levels of commitment.

Inclusions similar to Hirano bodies in urinary bladder neurons of dogs.

Unusual intracytoplasmatic inclusions were found in urinary bladder neurons in dogs. The plate-like inclusions were composed of thin filaments, and when viewed en face, appeared as oval or angular bodies with regular lattice work array. When viewed in a transverse section, they were of rod-like shape and were composed of longitudinal filaments and transverse bars. The inclusions were observed in all ganglia of the urinary bladders studied. Three-dimensional reconstruction of the inclusions was made, using a tilting device. By means of this reconstruction, it could be demonstrated that their ultrastructure is similar to that of Hirano bodies which occur in human neurons of the central nervous system in cases of neurodegenerative diseases. The authors suggest that unusual intraneuronal inclusions represent a peculiarity in cytoskeletal protein assembly typical of canine urinary bladder neurons.