Nerve growth factor (NGF) immunoreactive neurons in the juvenile rat hippocampus: response to acute and long-term high-light open-field (HL-OF) or forced swim (FS) stress stimulation.

This study aimed at examining and comparing the influence of two different stress stimuli on the density (number of cells/mm²) of nerve growth factor (NGF) containing neurons in the hippocampal CA1 and CA3 pyramidal cell layers and the dentate gyrus (DG) granule cell layer in juvenile rats (P28; P-postnatal day). The high-light open-field (HL-OF) test and forced swim (FS) test were employed to investigate the effects of a single, 15-min acute exposure and repeated (15 min daily for 21 days) long-term exposure to stress. In order to detect NGF-ir neurons, immunohistochemical (-ir) techniques were used. In comparison with nonstressed animals, acute and long-term HL-OF or FS stimulation resulted in a marked increase (P<0.001) in the density of NGF-ir containing cells in all the hippocampal structures. The frequency of stress application (acute vs. long-term), however, did not have a substantial impact on the studied parameter, with the exception of the CA3 sector, where a decreased density (P<0.001) of NGF-ir neurons was observed after long-term exposure to FS. It may be concluded that a rise in the density of NGF-ir neurons in the juvenile rat hippocampus after exposure to HL-OF or FS stressors could have affected the activity of the hypothalamic-pituitary-adrenocortical (HPA) stress axis. Prolonged HL-OF or FS stress was probably aggravating enough not to trigger the habituation process. The type of stressor applied (HL-OF vs. FS) was not essentially a factor determining the density of NGF-ir cells in the hippocampus.

Distribution of neuronal nitric oxide synthase (nNOS)-immunoreactive elements in the rabbit piriform cortex.

The piriform cortex (PC), the primary olfactory cortex, is involved in the processes of learning and stress response and possibly plays an important role in epileptogenic activity. The results of several recent studies suggest that those PC neurons that contain neuronal nitric oxide synthase (nNOS) may play a key role during spatial learning and in the modulation of initiation, propagation and generalisation of seizures in various experimental models and may influence neuronal vulnerability after epileptic insults. The aim of this study was to characterise the pattern of distribution and morphology of nNOS-immunoreactive elements in PC of the adult rabbit. The co-localisation of nNOS and calretinin (CR) was also studied. The pattern of nNOS-ir within the rabbit PC is similar to that described previously in other mammals. The morphology of nNOS-ir elements, namely varicose fibres and Cajal-Retzius cells, suggest that NO has an important influence on PC function. Surprisingly, in the rabbit PC nNOS-ir elements show a very low level of co-localisation with CR-ir.

The influence of storage time upon the real thickness of the histological brain sections.

The aim of the study was to assess the effect of storage time on the actual thickness of the histological sections. The study was performed on 5 brains of adult Wistar rats. The most rapid changes occur at the beginning of the storage process, after about one month the dynamics of changes decreases, but still the thickness of the sections diminishes. It is suggested that quantitative analyses should be performed in similar period of time and the critical care should be taken not only of the chemicals and procedures used, but also of the control of environmental factors.

Relation between the age of specimen and the shrinkage of brain frozen sections.

The aim of the study was to assess the effect of age of the animal upon the real thickness of the frozen sections. The study was performed on 19 rabbit brains. The thickness of the frozen sections regardless of their staining is age-dependent. The relation is proportional during the period from 7 to 180 postnatal day and characterizes both immunohistochemical as well as cresyl violet-stained sections; moreover, changes of the section thickness proceed parallelly. It is suggested that especially for some stereological parameters all required procedures should be standardized to achieve comparable and unbiasedly interpretable results.

Cholinergic endings on various neurones containing calcium binding proteins and glutamic acid decarboxylase in the hippocampus of the rat.

Immunohistochemical study of the cholinergic innervation of the hippocampal cells containing glutamic acid decarboxylase (GAD) and calcium binding proteins: parvalbumin (PV), calbindin D28k (CB) and calretinin (CR) was conducted on 5 adult rat brains. Analysis of sections with double immunostaining for vesicular acetylcholine transporter (VAChT; the marker of cholinergic cells, fibres and terminals) and respectively either GAD or PV, CB, CR, using confocal laser-scanning microscope shows that the intensive cholinergic innervations receive GAD, PV and CB-positive hippocampal cells. Cholinergic afferentiations of the CR-positive neurones are considerably fewer.