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Activation of the receptor 5-HT1A increases the rate of neurogenesis in the subventricular zone (SVZ) and its blocking reduces it. Cells generated in the SVZ settle in the olfactory bulb as its interneurons. We investigated in laboratory opossums if changes in the rate of SVZ neurogenesis infl uence olfactory detection of food and discrimination of conspecifi c odors. Four groups of one year old opossums were tested. The fi rst group was injected i.p. for 7 days with saline, the second group with 5-HT1A receptor agonist 8-OH-DPAT, the third group with partial agonist buspirone and the fourth group with the antagonist, WAY100635. BrdU was injected as a marker of newly generated cells. One month later opossums had to locate crickets hidden in the litter. Pretreatment with WAY100635 signifi cantly extended time needed for location of the hidden food in comparison to other groups. Next opossums were exposed for two days to samples of urine of two other opossums. Time of investigation of samples decreased with experience. Opossums injected with buspirone or WAY100635 investigated probes for a longer time and buspirone-treated approached them more frequently. There were no preferences for investigation of new odors. Post mortem investigation of the numbers of BrdU-labeled cells showed predictable differences. These results indicate that reduction of the rate of neurogenesis hampers olfactory detection of food, but detection of odors of conspecifi cs is infl uenced in more complex way
In adult mammals cells generated in the subventricular zone (SVZ) migrate to olfactory bulbs (OB). Functional significance of this continuous neurogenesis is not clear. We injected opossums (Monodelphis domestica) for seven consecutive days with a 5HT1A agonist (8-OH-DPAT or buspirone), or its antagonist WAY100635. One hour after each of these injections bromodeoxyuridine (BrdU), a marker of dividing cells was also injected. Two months later, when newly generated neurons settled in the OB and matured the ability of these opossums to detect hidden food by olfactory cues was tested. Afterwards, numbers of BrdU-labeled cell nuclei in their OB were counted and a phenotype of labeled cells established. In all groups investigated the majority of new cells differentiated into neurons (55-76%) and a lower proportion into astroglia (6-12%). Numbers of BrdU-labeled cells differed depending on the applied treatment: both agonists of the 5HT1A receptor increased these numbers, while its antagonist decreased them. The increased number of new OB interneurons did not change the time required for finding all three food items and therefore did not improve the opossums' performance in this test of the olfactory perception. However, opossums that had the reduced number of new generated OB cells searched longer for each food item and in consequence took three times longer to find all three crickets, than did opossums from other groups. In conclusion, lower numbers of new neurons in the opossums OB correlated with their worse behavioral performance in a test based on olfactory perception.
Interleukin 6 (IL-6) plays an important role in stress response and glucocorticoid action on the brain. It has been also shown that IL-6 plays a significant role in physiological and pathological brain development and is a crucial factor in the effects of prenatal immune challenge on physiological and behavioral abnormalities in adult offspring. We examined involvement of IL-6 in stressinduced changes in behavior and brain mechanisms in the adult mice. The PhenoRack system was used to non-invasively monitor mice home cage activity. Behavior of wild type mice C57BL/6J and IL-6 -/- knockout (IL-6 KO) mice were observed for 3 days using the PhenoRack system, which enables non-invasive monitoring of the mice home-cage activity (distance travelled, speeds and duration of movement, freezing). Mice were also subjected to standard behavioral tests. The open field test was used to establish the balance between exploratory behavior and anxiety evoked by the unknown, potentially dangerous situation. We measured the distance travelled in the open part of the arena, as well as time spent in it. We observed the sex-dependent effect of IL-6 on exploratory behavior. In all tested parameters IL-6 deficient females showed less anxiety than the wild type females. There was no difference in behavior in the open field between wild type and IL-6 deficient males. After finishing behavioral tests, the animals were killed with an overdose of pentobarbital and their brains were perfused transcardially with saline (0.9% NaCl) followed by 4% paraformaldehyde in 0.1 M phosphate buffer. The brains were cut on a cryostat into 40 µm sections and collected into 10 parallel series. Two of these series were stained with antibodies against glucocorticoid (GR) and mineralocorticoid (MR) receptors. One series from each brain was Nissl-stained for delineation of borders of the brain structures and evaluation of the number of cells in some of them. The number of hippocampal neurons and GRimmunopositive neurons in an area was estimated using the StereoInvestigator system (MicroBrightField Inc). Due to the crucial role of IL-6 in development of the hippocampus we evaluated the total number of cells in the CA1 field. We found that IL-6- deficient mice had significantly lower number of cells in the CA1 field and that almost all cells, unlike in wild-type mice, expressed the glucocorticoid receptor. Our preliminary results demonstrated that IL-6 is implicated in stress. Supported by the Polish National Science Center grant No 1577
INTRODUCTION: The grey short-tailed opossum, Monodelphis domestica is a laboratory animal useful in developmental research due to its slow and mostly postnatal growth. Little is known about marsupials brain development. AIM(S): The aim of the study was to investigate cerebellum development in the Monodelphis opossum. METHOD(S): We performed Nissl staining on the brain sectionsfrom opossumsin different age to see the overall pattern of cerebellum development. To find out when progenitor cells are present in this structure, we performed bromodeoxyuridine (BrdU) intraperitoneal injections in different time points. Phenotype of proliferating cells wasidentified by double immunofluorescence staining for a neuronal marker, NeuN or an astrocyte marker, GFAP and BrdU. RESULTS: We found that in the newborn Monodelphis opossum cerebellum is not yet morphologically formed. Immunostainig of BrdU-positive cells showed that Purkinje cells were generated between postnatal day (P) 1–5, whereas the highest rate of granule cells generation occurred between P11–P40. Double immunostaining revealed that the majority of BrdU-positive cells in the opossum cerebellum generated from P11 to P50 was neurons, as they showed colocalization with NeuN immunoreactivity. CONCLUSIONS: Our study shows that cerebellum development in the opossum is longer and more extended in time than in rodents. FINANCIAL SUPPORT: The work was supported by the National Science Center grant 2015/17/B/NZ4/02410.
Maternal deprivation model was used for studying the infl uence of perinatal stress on the behavior of adult mice. Swiss mice pups were separated from their mothers for two hours daily from postnatal day 1 (P1) to P7. One group of pups has been treated with buspirone immediately before each period of maternal separation (P1–P7). At the age of 1–3 months mice were subjected to a battery of behavioral tests. Then they were sacrifi ced, their brains were removed and used for immunohistochemistry staining or immunoblotting (Western blot) with antibodies directed against glucocorticoid or mineralocorticoid receptors. We found that in the open fi eld test and the plus maze test the stressed mice showed greater anxiety than non-stressed animals. Anxiety in stressed mice treated with buspirone was lower than in stressed only mice. Next, mice were tested either in a water maze test or an object recognition test where their memory and learning performance was assessed. We did not fi nd any signifi cant differences between groups in these two tests. These results demonstrate that stressing early life events, like maternal separation, permanently disturb emotionality of the adult mice but do not affect their learning or memory functions. Deleterious effects of stress may be prevented by pharmacological treatment. Supported by the Polish Ministry of Science and Higher Education grant No 3757/B/P01/2007/33.
In the brain of adult mammals neurogenesis continues in two regions: the dentate gyrus (DG) and subventricular zone of the lateral ventricles (SVZ). Here we present data concerning neurogenesis in brains of Rhinolophus (Rh) ferrumequinum, Rh euryale, Rh mehely and Rh hipposideros. These bats were captured on permission of the Ministry of Environment of Armenia. After capture all bats were injected with bromodeoxyuridine (BrdU, 300 mg/kg). Seven to nine days later animals were perfused transcardially with 4% paraformaldehyde in narcosis. We used immunohistochemical double-labeling to characterize the phenotype of newly generated cells. Colocalization of BrdU with NeuN (marker of mature neurons), glial fi brillary acidic protein (GFAP, astrocytic marker) and 2`,3`cyclic nucleotide phosphatase (CNP, oligodendrocytic marker) was examined using confocal microscope. We found that in both neurogenic regions the rate of neurogenesis was highest in Rhinolophus ferrumequinum and lowest in Rh mehely. Double-immunolabeling showed that in all neurogenic regions of the bats’ brain the neuronal phenotype dominated among newly generated cells, while proportion of astrocytes was low. BrdU colocalized with CNP in only a few cells in the SVZ of Rh ferrumequinum. We suggest that the rate of neurogenesis in different species may depend on the bats’ ecology.
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