Neuroscience
-
Dynorphins are endogenous opioid peptide products of the prodynorphin gene. An extensive literature suggests that dynorphins have deleterious effects on CNS injury outcome. We thus examined whether a deficiency of dynorphin would protect against tissue damage after spinal cord injury (SCI), and if individual cell types would be specifically affected. ⋯ Our results indicate that dynorphin peptides affect the extent of post-injury caspase-3 activation, and that glia are especially sensitive to these effects. By promoting caspase-3 activation, dynorphin peptides likely increase the probability of glial apoptosis after SCI. While normally beneficial, our findings suggest that prodynorphin or its peptide products become maladaptive following SCI and contribute to secondary injury.
-
Hippocampal granule cells (GCs) are continuously generated in the subgranular zone of the dentate gyrus (DG) and functionally incorporated to dentate neural circuits even in adulthood. This raises a question about the fate of neonatally born GCs in adult DG. Do they exist until adulthood or are they largely superseded by adult-born GCs? To investigate this question, we examined the contributions of postnatally born GCs to the adult mouse DG. ⋯ We defined BrdU- and Prox1-double positive cells as newborn GCs and analyzed their density and distribution in the granule cell layer (gcl), revealing that newborn GCs of each group still existed 6 months after BrdU injections and that the density of GCs born during P0-2 (group 1) was significantly higher compared with the other groups. Although the density of newborn GCs in the each group did not differ between male and female, the radial distribution of them in gcl showed some differences, that is, male newborn GCs localized toward the molecular layer compared with female ones in group 1, while to the hilus in group 2. These results suggest that GCs born in early postnatal days numerically dominate adult DG and that there exist sex differences in GC localizations which depend on the time when they were born.
-
The expression pattern of the pannexin2 protein (Px2) in healthy and ischemized brains of adult rats was investigated. A polyclonal antibody for rat Px2 was generated in chicken and purified for affinity. This antibody was used to study by Western blot, Enzyme-Linked Immunosorbent Assay, and immunohistochemistry, the expression pattern of Px2 in healthy brain of adult rats and in the hippocampus of rats submitted to bilateral clamping of carotid arteries for 20 min, followed by different times of reperfusion (I/R) (8 h, 24 h, 48 h, 72 h, 14 days and 30 days). ⋯ These results suggested the expression of Px2 in the astrocytes may be induced either from injured neurons or by biochemical pathways internal to the astrocyte itself. In conclusion, our results showed the transient expression of Px2 in astrocytes of reactive gliosis occurring in the hippocampus following I/R injury. We hypothesize that Px2 expression in astrocytes following an ischemic insult is principally involved in the formation of hemichannels for the release of signaling molecules devoted to influence the cellular metabolism and the redox status of the surrounding environment.