Search

The amygdala is a critical component of the neuroanatomical stress circuit. It plays a role in the generation of responses to emotional stimuli. The central (CeA) and medial (MeA) amygdaloid nuclei are implicated in activation of the hypothalamic-pituitary-adrenocortical (HPA) axis. The immunoreactivity (-ir) of c-Fos, NGF and its receptor, TrkA, following acute and chronic open-field stress were studied in the CeA and MeA nuclei of the amygdala. The material consisted of 21 male adult rats divided into three groups: non-stressed (control) animals, rats exposed to acute (once only lasting 15 min) and chronic (15 min daily over 21 days) aversive stimulation (open-field exposure). The brains were stained with the use of immunohistochemical methods for c-Fos, NGF or TrkA. In the control rats c-Fos-, TrkA- and NGF-ir cells were observed in the nuclei studied, but the quantity varied, being moderate or high (immunoreactive to TrkA and NGF) or low (immunoreactive to c-Fos). In the animals exposed to acute open-field stress the number of c-Fos-ir, NGF-ir and TrkA-ir cells in the nuclei under examination was differentiated but higher than that in the control animals. In the animals exposed to chronic open-field stress the number of c-Fos-ir cells in the nuclei studied was similar and was smaller than those in animals exposed to acute stress. The number of TrkA-ir neurons was also lower in comparison to that in animals exposed to acute stress. However, no significant differences in the number of NGF-ir cells were observed between the groups exposed to acute and chronic stress. Diverse expression of c-Fos protein following both acute and chronic stress stimulation may prove the functional heterogeneity of the amygdaloid nuclei investigated. The decrease observed in both c-Fos- and TrkA-ir in MeA (only TrkA in CeA) of animals exposed to chronic stress may indicate the phenomenon of habituation. [ABSTRACT FROM AUTHOR]

Coffee and nicotine consumption are frequently combined, indicating possible intensifying effect of caffeine on smoking behavior, although neurobiological background of this phenomenon remains unknown. We aimed at determining the effect of caffeine and nicotine, applied separately or simultaneously, on activation of six structures of the brain reward system: nucleus accumbens (NAc), ventral tegmental area (VTA), amygdala (Amg), hippocampus (Hip), medial prefrontal cortex (mPfr) and dorsal striatum (CdP) in the adult male Wistar rats. Activation of two transcription factors, the phosphorylated form of cyclic AMP-response element binding protein (pCREB) and DeltaFosB (ΔFosB) was assessed by immunohistochemistry after multiple-dose five-days psychostimulants administration followed by 20min and 24h survival, respectively. Nicotine evoked the highest increase of pCREB-immunoreactivity (-ir) in NAc, while caffeine exerted the weakest effect in mPfr and CdP. Nicotine/caffeine co-administration resulted in decrease of pCREB-ir in NAc and increase in Amg, compared with the effect of each psychostimulant used separately. Nicotine was the strongest psychostimulant activating ΔFosB-ir in Amg, whereas caffeine - in Hip. Nicotine/caffeine-exerted effect upon ΔFosB-ir in Amg was weaker, whereas in mPfr stronger, than nicotine-evoked effect in these structures. In summary, pCREB and ΔFosB activation is dependent on the type of stimulus, brain structure and functional context. Activation of both transcription factors is responsible for caffeine's modifying effect upon nicotine-related behaviors and must be taken into account while quitting cigarette smoking., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The way hippocampal neurons function during stress in old age (critical times of life) is dependent on brain derived neurotrophin factor (BDNF). This study examined the influence of acute and chronic forced swim (FS) or high-light open field (HL‑OF) stimulation on the density of BDNF immunoreactive (ir) neurons in the hippocampal pyramidal layers of CA1, CA2, CA3 regions and the granular layer of dentate gyrus (DG) in old (postnatal day 720; P720) Wistar Han rats. Our data showed that in comparison with non-stressed rats, acute FS caused a significant increase in the density of BDNF-ir neurons in CA2 and CA3, while acute HL-OF led to an increase in this factor in all hippocampal subfields with the exception of DG. However, the density of BDNF-ir cells remained unchanged after exposure to chronic FS or HL‑OF in the hippocampal regions in relation to the control rats. These results indicate that acute FS or HL-OF proved to be a stressor that induces an increase in the density of BDNF-ir pyramidal neurons, which was probably connected with up-regulation of HPA axis activity and short‑time memory processing of the stressful situation. Moreover, as far as the influence on BDNF-ir cells in hippocampus is concerned, chronic FS or HL-OF was not an aggravating factor for rats in the ontogenetic periods studied.

It seems that age-dependent changes in stress response may be correlated with alterations in the hypothalamic brain derived neurotrophin factor (BDNF). Two hypothalamic nuclei, ie. paraventricular (PVN) and supraoptic (SON) are closely related to the stress response. Therefore, the aim of our study was to explore the influence of acute and chronic high-light open field (HL-OF) or forced swim (FS) stimulation on the density of BDNF immunoreactive (ir) neurons in the PVN and SON in adult (postnatal day 90; P90) and aged (P720) Wistar Han rats. Our data demonstrated that in comparison with non-stressed rats, neither acute nor chronic FS caused significant changes in the density of BDNF-ir neurons of PVN and SON in P90 or P720 rats. However, a significant increase in the density of BDNF-ir neurons in the SON of P90 and a decrease in the PVN of the P720 rats were noted after acute HL-OF. Despite the lack of change in the density of BDNF-ir neurons between P90 and P720 non-stressed and FS stressed rats, there was an age-dependent decrease in the BDNF-ir cells of HL-OF stressed rats, especially in the PVN. We may conclude that in terms of its influence on the BDNF-ir neurons in PVN and SON, acute HL-OF was the factor inducing changes in the density of BDNF-ir neurons in the hypothalamic nuclei of adult or aged rats. Furthermore, ageing involutional processes, which can impair hypothalamic-pituitary-adrenal axis functioning, may have been able to cause an age-related decrease in the BDNF-ir PVN and/or SON neurons in HL-OF stressed rats., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Nerve growth factor (NGF) seems to play an important role in the ageing limbic system in response to stress. This study aimed to explore the influence of acute and chronic exposure to high-light open field (HL-OF) or forced swim (FS) stressors on the density of NGF immunoreactive (ir) neurons in the amygdala central (CeA), medial (MeA), lateral (LA) and basolateral (BLA) nuclei in adult (postnatal day 90; P90) and aged (P720) rats. In comparison with non-stressed rats, neither acute nor chronic HL-OF produced significant changes in the density of NGF-ir neurons of studied nuclei in P90 and P720 rats. However, not acute but chronic FS was the factor inducing an increase in the density of NGF-ir neurons in the CeA of both age groups and in the LA of P720 rats. Despite the lack of change in the density of NGF-ir neurons between P90 and P720 non-stressed rats, there were significant age-related changes in NGF-ir cells in FS and/or HL-OF stressed rats in all the tested nuclei, with the exception of the LA. It may be concluded that as far as the influence on NGF-ir cells in amygdaloid nuclei is concerned, HL-OF did not constitute an aggravating factor for rats in the ontogenetic periods studied. Moreover, upregulation of NGF-ir neurons predominantly in CeA after chronic FS seems to be neuroprotective. Age-dependent changes in the density of NGF-ir neurons in stressed rats are probably caused by ageing processes and they may point to dysregulation of excitatory control exerted by the amygdala., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The ontogenetic period of life and stress can have different effects on the nerve growth factor (NGF) in the hypothalamus. The aim of our study was to investigate the influence of two mild stressors, acute and chronic exposure to forced swim (FS) or high-light open field (HL-OF), on neurons containing NGF. Immunofluorescence staining was used to reveal the density of NGF-immunoreactive (ir) cells in the hypothalamic supraoptic nucleus (SON) in adult (postnatal day 90; P90) and aged (P720) rats. The P90 and P720 rats that were subjected to acute and chronic FS showed no differences in the density of NGF-ir neurons in the SON compared with nonstressed rats. However, a significant increase in NGF-ir cells was noted after acute but not after chronic HL-OF only in P90 rats. What is more, there were no age-related (P90 vs. P720) changes in the density of NGF-ir neurons in non-stressed and FS- or HL-OF-stressed rats. Our results indicate that acute HL-OF was the only factor inducing changes in the density of NGF-ir neurons in the SON of adult rats. This could be related to the neuroprotective role of NGF-ir cells in response to acute HL-OF. The absence of age-dependent changes in the density of NGF-ir neurons may indicate that the ageing processes in SON do not generate changes in the NGF immunoreactivity of its neurons.

Proinflammatory cytokine - interleukin 1β (IL-1β) plays an important role in stress reactions in the structures of limbic system. The impact of stress on IL-1β may depend on the ontogenetic age. The study examined the influence of acute and chronic exposure to forced swim (FS) or high-light open-field (HL-OF) stressors on neurons containing IL-1β. Double immunofluorescence staining was used to reveal the density of IL-1β/NeuN (NeuN - a neuronal nuclear marker) - immunoreactive (ir) cells in the amygdaloid central (CeA) and medial (MeA) nuclei, which are closely involved in the regulation of emotional stressors and hypothalamic-pituitary-adrenal axis (HPA) activation. Adult (P90; P - postnatal day), middle-aged (P360), and aged (P720) male Wistar Han rats were used in these experiments. We observed an age-dependent increase in the basal density of IL-1β/NeuN-ir cells in CeA and MeA in P90 vs. P360 and P360 vs. P720 rats. Neither acute nor chronic FS caused significant changes in the density of IL-1β-ir neurons in any of the investigated nuclei in P90, P360, and P720 rats as compared with the non-stressed groups. However, chronic but not acute HL-OF caused a marked increase in the density of IL-1β/NeuN-ir cells in the CeA and MeA of P360 rats and in MeA of the P720 animals. Moreover, chronic HL-OF led to an increase in the density of IL-1β-ir neurons in relation to acute HL-OF in the CeA and MeA of both P360 and P720 rats. Our results may indicate the involvement of IL-1β neurons in the development of ageing processes in CeA and MeA. Furthermore, our results point out that chronic HL-OF is an aggravating factor that induces an increase in the density of IL-1β/NeuN-ir cells in the MeA and/or CeA of middle-aged and aged rats. The increase is possibly due to insufficient control of the HPA axis associated with involutional ageing processes and seems to be a common denominator of the ageing process and stress.

It is believed that the impact of stress on interleukin-1β (IL-1β) depends on the ontogenetic age. This study examines the influence of acute or chronic exposure to forced-swim (FS) stress or high-light open-field (HL-OF) stimulation on the expression of IL-1β. Double immunofluorescence staining was used to reveal the density of IL-1β/NeuN (NeuN is a neuronal nuclear marker)-immunoreactive (-ir) cells in the hippocampal subfields CA1 and CA3, dentate gyrus (DG), and paraventricular nucleus (PVN) of the hypothalamus. Adult postnatal day 90 (P90) and aged (P720) rats were used in this experiment. The data showed a significant increase in the density of IL-1β/NeuN-ir cells in the CA1, CA3, DG, and PVN in P720 nonstressed rats in relation to P90 control animals. Neither FS nor HL-OF acute stimulation caused alteration in the density of IL-1β-ir neurons in any of the investigated structures in P90 and P720 rats in comparison with control groups. However, chronic FS caused a significant increase in CA3 and DG of P720 rats, and chronic HL-OF led to a significant increase in the density of IL-1β-ir neurons in the PVN of P90 rats and in all hippocampal subfields of P720 animals. These results indicate that chronic HL-OF stimulation is a factor that induces changes in the number of IL-1β-ir neurons in the PVN of adult rats, whereas both chronic FS and HL-OF are aggravating factors for the hippocampus of aged (P720) animals., (Copyright © 2014 Wiley Periodicals, Inc.)

It is postulated that stress differentially affects interleukin-1beta (IL-1beta) during ontogenetic life. This study examined the influence of chronic exposure to forced swim (FS) stress or high-light open-field (HL-OF) stress on interleukin-1beta (IL-1beta). The total level of IL-1beta protein was assessed by Western blot analysis of hippocampal extracts. Double immunofluorescence staining was used to reveal the percentage of IL-1beta/NeuN (NeuN - neuronal marker) cells in the CA1, CA3 and dentate gyrus (DG) hippocampal subfields. Juvenile (P28; P - postnatal day) and middle-aged (P360) rats were used in the experiment. The research showed no significant differences in IL-1beta protein levels between P28 and P360 non-stress rats. However, a substantial increase in the percentage of IL-1beta-ir neurons in the CA1, CA3 and DG in P360 rats was observed. Chronic FS had no significant influence on IL-1beta expression in the hippocampus or on the percentage of IL-1beta-ir neurons in CA1, CA3 and DG hippocampal subfields in either age group. During HL-OF, the IL-1beta level was significantly increased in the hippocampus of P28 and P360 rats, whereas a marked increase in the percentage of IL-1beta-ir neurons in the CA1, CA3 and DG hippocampal areas occurred only in P360 animals. These results indicate that chronic HL-OF stimulation was the factor inducing changes in the IL-1beta protein levels in P28 and P360 rats and in the percentage of IL-1beta/NeuN-ir cells in the hippocampus of P360 animals.

Calbindin-D28k (CB), parvalbumin (PV) and calretinin (CR) are calcium-binding proteins (CaBPs) considered to be markers for certain subpopulations of neurons in the central nervous system. The aim of this study was to describe the pattern of distribution of CB-, PV- and CR-immunoreactive elements in the rabbit corticomedial amygdaloid complex during the postnatal period. The time course of changes in CaBPs expression during maturation of the selected nuclei indicates their diversity. During the first month after birth, CaBPs expression stabilizes earliest in the anterior cortical and then in the medial nuclei. Later, during the second month of postnatal life, the posteromedial and posterolateral cortical nuclei maturate. The central nucleus requires a considerably longer time to reach maturity - about three months are needed to stabilize CaBPs expression in all its subdivisions. This nucleus also shows the most differentiated, time-dependent distribution of CaBPs immunoreactivity (especially CB), distinct in its divisions. The differences in the CaBPs immunoreactivity confirm previous reports concerning dissimilar origin and development, and also reflect the diversity of connectivity of the amygdaloid body - the collection of nuclei, considered as one functional integrity.

We investigated distribution and morphology of neurons of the midbrain nuclei: the ventral tegmental area (VTA), substantia nigra (SN) and periaqueductal gray (PAG) of the adult grey short-tailed opossums that were double immunolabeled for the presence of calretinin (CR) and/or tyrosine hydroxylase (TH). The majority of TH-immunopositive neurons and fibers were located in the VTA, SN, and only scarce population of small neurons expressing TH was present in the PAG. In the SN 80 percent of TH-expressing neurons had large cell bodies, and only a small fraction had small perikarya. In the PAG populations of large and medium sized neurons were equal and 20 percent of neurons had small perikarya. Much scarcer population of TH-immunoreactive neurons in the PAG consisted of large or small neurons in its dorsal part (PAGd) and almost exclusively small neurons in the ventral part (PAGv). Distribution of neurons expressing TH and their types in the opossum are similar to those in rodents. The majority of CR-immunolabeled neurons were found in the VTA. In its subdivision, the parabrachal pigmented nucleus (PBP) cells expressing CR were approximately 28 percent more numerous than cells expressing TH. In spite of that, only 42 percent of TH-expressing neurons coexpressed CR. The high degree of colocalization TH and CR was observed in the SN. We propose that a higher percentage of TH/CR colocalization, which is observed in the opossums SN, may give them the ability to adapt to changes in their motor functions.

Our study aimed to explore the influence of two different stressors: acute (once for 15 min) and chronic (15 min daily for 21 days) exposure to high light open field (HL-OF) or forced swim (FS) on the density of nerve growth factor (NGF) and tyrosine kinase A (TrkA) immunoreactive neurons in the hippocampal CA1 and CA3 pyramidal cell layers and dentate gyrus (DG) granule cell layer in middle aged (360 days old; P360; P, postnatal day) rats. In contrast to non-stressed animals, acute HL-OF stimulation resulted in an increase (p<0.001) in the density of NGF-ir cells in CA1, CA3, DG, whereas chronic HL-OF produced no changes in all hippocampal regions. The rats which underwent acute and chronic FS tests showed no statistically significant differences in the density of NGF-ir containing cells in the CA1, CA3, and DG subfields compared with control rats. Except for DG, where after 21 days of FS the density of TrkA-ir neurons was found to increase (p<0.05) in comparison to unstressed rats, no changes were noted in the density of TrkA-ir in the studied hippocampal structures as a result of acute and chronic HL-OF or FS exposure. These results indicate that acute HL-OF stress stimulation was the only factor inducing changes in the density of NGF-ir containing neurons in the hippocampal CA1, CA3, and DG of middle aged rats. In respect of the density of NGF-ir and TrkA-ir cells in the hippocampal structures, prolonged exposure to HL-OF or FS stressors did not constitute an aggravating factor for rats in the studied ontogenetic period., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The aim of our study was to analyze the influence of the open field (OF) exposure on: 1. Distribution of c-Fos positive nuclei in: ventral tegmental area, substantia nigra, periaqueductal gray. 2. Appearance of calbindin-D28k, calretinin and parvalbumin in midbrain neurons that are engaged in the stress response. 3. Changes of c-Fos and calcium-binding proteins expression during maturation. The material consisted of Wistar rats of age between 0 and 90 days. The OF exposure was applied throughout 10 min and 90 min before the death of the animals. The brain sections were double stained using the antibodies against c-Fos, CB, CR or PV. Our results showed that in all studied nuclei age-related increase of c-Fos expression (without changing of its distribution properties) was found. PV didn't show any co-localization with c-Fos in neurons of studied regions at any ages, however some PV-immunoreactive (PV-ir) basket-like structures around c-Fos-immunoreactive (c-Fos-ir) neurons were observed. In the youngest group of rats c-Fos-ir cells and cells immunoreactive for CB and CR constituted separate neuronal populations. During maturation increases in the level of their co-localization with c-Fos was observed. We may conclude that in adult rat midbrain structures CB-immunoreactive (CB-ir) and CR-immunoreactive (CR-ir) cells (probably projection neurons) are mainly activated in the stress response following OF exposure. In the contrary PV-ir cells has only an indirect (modulatory) influence upon the c-Fos-ir cells.

The immunoreactivity (ir) for c-Fos, NGF and TrkA, following an acute and chronic open field stress, were studied in the periventricular zone of rat hypothalamus. Adult rats were divided into three groups: control, exposed to acute (single exposure--15 minutes) and chronic (multiple exposures--15 minutes daily for 21 days) open field stress. In the control rats neurons immunoreactive to c-Fos, TrkA and NGF were found. The number of TrkA- and NGF-ir cells was high, whereas this of c-Fos-ir ones was low. In animals exposed to acute open field stress the number of c-Fos-ir cells in the examined nuclei varied, however it was much higher than that in the control animals. The number of TrkA-ir neurons in all the studied nuclei was also higher than that in the control animals, but the increase of the number of NGF-ir neurons was not observed in supraoptic nucleus. In the animals exposed to chronic open field stress the number of c-Fos-ir cells was increased in comparison to that in the control rats. After chronic stress exposure the number of TrkA-ir neurons in supraoptic nucleus remained high in comparison to that in animals exposed to acute stress, whereas it was decreased in other studied nuclei. No significant differences in the number of NGF-ir cells were observed between the groups exposed to the acute and chronic stress. Observed decrease of c-Fos- and TrkA-ir in the studied nuclei in the animals suffering from chronic stress in comparison with the acute one may indicate the occurrence of habituation phenomenon. This phenomenon does not concern NGF-ir.

The glial cells play an important role in pathophysiology of the intracerebral haemorrhage (ICH). Thus the attempt at evaluating the possible influence of the propofol on the reactivity of astro- and microglial cells in the course of ICH was performed. 50 rats were divided into two groups depending on the applied anaesthesia. All animals were generally anaesthetized with fentanyl, dehydrobenzperidol and midazolam. No additional agents were given to the animals of the control group (group I). In the experimental group (group II), the animals received additionally intraperitoneally propofol in a dose of 50 mg/kg every thirty minutes. ICH was produced through infusion of the blood into the striatum. The astrocytic and microglial cells population was assessed on the 1, 3, 7, 14 and 21 days after producing a haematoma using antibodies anti-GFAP and OX42. The stereological analysis was applied to estimate the numerical density of immunoreactive cells and the distribution of their types. On the 14th and 21st days of observation the density of GFAP-immunoreactivity (ir) cells was significantly higher in group II than that in group I. There were no differences in percentage distribution of GFAP-ir astrocytes between group I and group II. On the 3rd, 14th and 21st days of observation the density of OX42-ir cells was higher in group II in comparison with group I. For the 7th, and 21st days of survival the percentage of the ameboid form of OX42-ir cells was significantly lower in group I than that in group II. The administration of propofol during anaesthesia in the animals with ICH has evoked an increase of the activation of the astro- and microglial cells.

40 adult Wistar rats were divided into two groups depending on the applied anaesthesia. In both groups animals were generally anaesthetized with fentanyl, dehydrobenzperidol administered intraperitoneally and midazolam given intramuscularly. In the second group (SEVO) animals received sevoflurane of 2.2 vol% end-tidal concentration. Intracerebral haematoma was produced through infusion of 100 microl of autologous blood into the striatum. Each group was divided into five subgroups depending on the length of survival period: 1, 3, 7, 14, 21 days. The astrocytic population was studied by means of anti-GFAP staining. Stereological analysis was applied to estimate the numerical density of immunoreactive cells and the distribution of their types. On 7th day of observation the density of GFAP-immunoreactive astrocytes in SEVO was lower (p<0,05) than that in the control group. In the control group, the increase (p<0.05) of per cent of activated astrocytes between the 1st and 3rd survival day was noted, which remained at this level till the end of observation. In SEVO group, the increase (p<0.05) of per cent of activated astrocytes between the 3rd and 7th day and the decrease (p<0.05) between the 14th and 21st survival day were observed. During days of observation the per cent of activated astrocytes was lower (p<0.05) in the SEVO group than that in the control group. Administration of sevoflurane during anaesthesia to animals with intracerebral haemorrhage has evoked not only the delay of the activation of astrocytes but also decrease in its level.

In the present study we wanted to check whether the expression of the c-Fos protein (the marker of cellular activity) appears in cells containing calcium-binding proteins (CaBPs) in animals exposed to the open field test. Eight adult Wistar rats were examined. In the first step the open field test was applied throughout 10 minutes. After perfusional fixation brains were frozen and cut on the cryostat in the coronal plane and stained with the standard immunohistochemical method. Sections were double stained for c-Fos and CaBPs: parvalbumin (PV), calbindin (CB), calretinin (CR). c-Fos positive cells were localized predominantly in layers II and III of the piriform cortex (PC). The double labeling study showed that neurons containing CaBPs are rarely c-Fos-immunoreactive. Often PV-positive and CB-positive fibers surround c-Fos-positive neurons in layers II and III in a form of a basket. It seems that cells containing CaBPs are not directly involved in the response to aversive stimuli but cells containing those calcium-binding proteins might influence directly c-Fos positive neurons of PC.

In our study we used c-Fos protein to identify whether cells containing calretinin (CR) in the rat piriform cortex are engaged in the response to stress stimulation and to find out how this expression changes during maturation (PC). The material consisted of Wistar strain rats of between 0 and 120 days of age divided into 9 groups. Each group consisted of 5 experimental and 3 control rats. Animals from the experimental groups were exposed to the open field test throughout 10 minutes. The control animals were kept in a home cage. In all age-related control rats weak c-Fos immunoreactivity was observed. Our results showed that cells containing c-Fos following an acute open field test were observed predominantly in layers II and III of the PC just after birth. Their number then increased and stabilised on P30. We had already observed immature CR-ir cells at birth. In the 4th week of life these neurons achieved maturity. Their number increased to P90 and decreased in older animals. CR-ir neurons were localised mainly in layer II and to a lesser degree in layers III and I of the PC. Double immunostaining c-Fos/CR revealed that the level of co-localisation was low. Only small differences were observed between the anterior and posterior parts of the PC. In the anterior part a higher number of CR-ir neurons was found. The difference in the level of co-localisation between the anterior and posterior parts was age-related and differentiated. Our results may suggest that during maturation CR-ir neurons of the piriform cortex are not the main population engaged in response to the open field test.

In our study we used c-Fos protein (as a marker of cellular activity) to identify whether cells containing parvalbumin (PV) in the piriform cortex (PC) are engaged in the response to stress stimulation and to discover how this expression changes during maturation. The material consisted of Wistar rats of postnatal (P) ages between 0 and 120 days divided into 9 groups: P0, P4, P7, P10, P14, P21, P30, P90, P120. Each group consisted of 5 experimental and 3 control animals. Rats of the experimental groups were exposed to the "open field test" throughout 10 minutes. The control animals were kept in a home cage. Our results showed that c-Fos activity in the open field test was observed in layers II and III of PC after birth. It then increased and stabilised on P30. In the second week of life PV-positive cells were also observed in those layers. These achieved maturity in the 4th week of life. After this time basket-like structures appeared but the level of PV/c-Fos co-localisation was low. Only small differences were observed between the anterior and posterior parts of PC. In the anterior part a higher number of PV-positive neurons, neuropil threads, and basket-like structures and a larger degree of PV/c-Fos co-localisation were observed. Our results suggested that during maturation PV cells are not directly activated in response to stress stimuli but PV neurons via their numerous endings influence the activation of c-Fos-positive cells predominantly in the anterior part of PC.

Our intention in the present study was to ascertain whether NO-producing cells in the basolateral complex (BLC) and paracapsular intercalated nerve cell groups (Ip) of the amygdala are activated in the open field (OF) test. The material consisted of 8 adult rat brains. The OF test was applied throughout 10 min and 90 min before the death of the animals. The brain sections were double stained using the antibodies against c-Fos (marker of neuronal activation) and against nitric oxide synthase (NOS -- marker of NO-producing cells). The neurons containing NOS and those revealing c-Fos activity constituted distinct populations within both the BLC and Ip but NOS-immunoreactive fibres often surrounded the c-Fos-immunoreactive neurons. Our results suggest that (1) neurons of the basolateral complex of the amygdala and paracapsular intercalated islands are involved but probably not crucial for the open field stress response and (2) NOS-immunoreactive cells in the BLC and Ip are not activated after OF exposure.

The piriform cortex has been extensively studied due to its possible role in epileptogenic activity. Neurones containing calcium-binding proteins (CaBPs), as a component of inhibitory circuitry, seem to be critically involved in this pathological process. The aim of the present study was to characterise the pattern of distribution of CaBPs-immunoreactivity in the piriform cortex of the adult rabbit. It comprises labelled cells, fibres (often with varicosities) and terminals. It varies among the layers. Moreover, the distribution of the parvalbumin- and calretinin-immunoreactive fibres and terminals allows even further subdivision of the layer I into two sublayers. Calretinin-ir neurones are located in subpial (Ia) layer, while parvalbumin - as well as calbindin-D28k-ir ones are mainly located in the second and third layer. Cajal-Retzius-like neurones containing calretinin, Chandelier cells containing parvalbumin and basket cells containing calbindin D28k and parvalbumin can be distinguished among labelled subpopulations of CaBPs neurones. In general, the pattern of PV- CR- and CB-immunoreactivity is similar to that previously characterised in other mammals, i.e., rats, guinea pigs, hedgehog, and tenrecs. The pattern is organised in topographic fashion confirming the complexity of regulatory circuits in the rabbit piriform cortex.

The present paper describes parvalbumin, calbindin-D28k and calretinin immunoreactivity in the claustrum and endopiriform nucleus of adult rabbits. Studied neuronal populations are characterized by morphological heterogeneity. Four types were identified in each subpopulation of cells containing calcium binding proteins on the basis of the number of processes and their branching pattern. There were no spatial differences in the distribution of cells containing either parvalbumin or calbindin-D28k in the claustrum and endopiriform nucleus. Well documented presence of the various projective zones in the rabbit claustrum did not reflect the specific distribution of neurons containing calcium binding proteins, except those containing calretinin. Their localization may correspond with the limbic zone. We have found that the rabbit claustrum and endopiriform nucleus have different pattern of parvalbumin and calretinin immunoreactivity. The former was more intense in the claustrum and the distribution of cell types was significantly different from that in the endopiriform nucleus. Calretinin-positive cells were observed in the claustrum, while in the endopiriform nucleus they were scarce. The distribution of neither calbindin-D28k-ir neurons nor fibers allowed differentiation of claustrum and endopiriform nucleus. Significant differences between the claustrum and endopiriform nucleus observed in the rabbit might be related with ontogenetic as well as other (functional) factors.

Ventral tegmental area (VTA) is a heterogeneous group of dopaminergic cells which contains interfascicular (IF), parabrachial (PBP) and rostral linear (RLi) nuclei. Neurons of this area are involved in the regulation of motor and motivational aspects of behavior and reveal high neuronal plasticity. Among many various neurotransmitters and neuromodulators, nitric oxide (NO) is localized in this region. In the present study, we investigated morphology and distribution of nitric oxide synthase (NOS)-positive neurons in VTA and their colocalization with dopaminergic neurons. The study was performed on six adult Wistar rats. After perfusional fixation, the brains were cut, immunostained for tyrosine hydroxylase (TH) and NOS and studied by confocal laser microscopy. In each of the three studied nuclei of VTA we investigated three different neuronal populations. Numerous TH-immunoreactive (TH-ir) and NOS-immunoreactive (NOS-ir) neurons are present in the studied region. Among them, a considerable number showed coexistence of both neurotransmitters. The populations of TH-ir and NOS-ir neurons interact with each other as manifested by the presence of NOS-ir endings on TH-ir neurons and vice versa. Taking the above into account, it may be suspected that NO is involved in the modulation of dopaminergic transmission.

We examined the protein expression of the calcium-binding protein calbindin D28k in two developing rat brain structures, the striatum and the cerebral cortex. The relative protein concentration level was quantified by means of the Western blotting method and densitometric scanning. 32 Wistar rats were used, divided according to survival period (P0-P120-postnatal days). Observations of the calbindin D28k protein expression in the rat striatum and the cerebral cortex revealed an increase in band color intensity between P0 and P10. The intensity of protein staining in older groups of animals stabilised at a similar level and in the P28 and P120 groups we observed a decrement of calbindin expression in the striatum. Calbindin D28k stabilises the intracellular calcium level, preventing calcium-induced apoptotic cell death in neurons. Thus, changes in calbindin D28k expression might be related to its neuroprotective role in differentiation and synaptogenesis during the postnatal development of the brain.