[Nitric oxide promotes the differentiation of neural stem cells in vitro derived from the subventricular zone of neonatal rats]

OBJECTIVE

To observe the effect of nitric oxide (NO) on the differentiation of neural stem cells (NSCs) derived from subventricular zone (SVZ) of neonatal rats in vitro.

METHODS

Conventional method was used to isolate and culture the NSCs from SVZ. Diethylenetriamine/NO(DETA/NO) was used as NO donor and Nitro-L-arginine methylester (L-NAME) was used as inhibitor of nitric oxide synthase (NOS). The immunofluorescence was used to identify the expression of nestin (a marker of NSCs), beta-III-tubulin (Tuj-1, a marker of neurons), glial fibrillary acidic protein (GFAP, a marker of astrocytes) and nNOS. The concentration of NO in medium was measured by Greiss assay.

RESULTS

Cultured neurospheres were nestin-, BrdU- and nNOS-positive. After treatment with 40 micromol/L, 50 micromol/L and 60 micromol/L of DETA/NO for 5 days, the concentration of NO released was increased significantly (P < 0.01) as compared with that of the control group. The percentage of both differentiated neurons and astrocytes was increased significantly (P < 0.01 and P < 0.05) as compared with that of the control group. After treatment with 100 micromol/L, 150 micromol/L and 200 micromol/L of L-NAME for 5 days, the concentration of NO released was decreased as compared with that of the control group (P < 0.05). The percentage of both differentiated neurons and astrocytes were decreased as compared with that of the control group (P < 0.05).

CONCLUSION

NO could directly promote the differentiation of NSCs derived from rat subventricular zone in vitro.

Inducible expression of functional mu opioid receptors in murine dendritic cells

Opioids are known to exert direct effects on the immune system, and the expression of functional opioid receptors has been reported on several immune cell types. Dendritic cells (DCs) are important inducers and regulators of immune responses. In this study, we investigated whether murine dendritic cells express functional mu opioid receptors (MOR). RT-PCR analysis and double immunofluorescence staining revealed the expression of MOR in activated murine dendritic cells. We also studied the dynamic expression of MOR messenger RNA in murine dendritic cells in response to different Toll-like receptor ligands. Functionally, treatment of DCs with endomorphin 1 (EM1), a specific agonist of MOR, can inhibit the forskolin-induced formation of cyclic adenosine monophosphate level in activated DCs. Moreover, EM1 treatment resulted in less activation of p38 MAPK and more activation of ERK signaling in lipopolysaccharide-stimulated DCs. Consistently, treatment of DCs with EM1 altered cytokine production by increasing IL-10 and decreasing IL-12 and IL-23. Our results suggest that MOR is inducibly expressed on activated DCs and functionally mediates EM1-induced effects on DCs. Thus, dendritic cells might be involved in crosstalk between the neuroendocrine and the immune system.

Forced running enhances neurogenesis in the hippocampal dentate gyrus of adult rats and improves learning ability

To investigate the effect of forced running in motor-driven wheel on neurogenesis in the hippocampal dentate gyrus (DG) of adult rats, 5-bromo-2-deoxyuridine (BrdU), a thymidine analog was applied to mark cell proliferation. Neuroepthelial stem cell protein (nestin) expression was used to identify neural stem/precursor cells. The BrdU- and nestin-positive cells were examined by immunohistochemical technique. The ability of learning was evaluated by Y-maze test to explore the functional role of the newborn cells in the DG after forced running. It was found that the number of BrdU- and nestin-positive cells in the DG in running groups was significantly increased compared to that in the control group (P<0.05). The effect of forced running on neurogenesis was intensity-dependent. In addition, an improvement of learning ability in Y-maze test was observed after forced running. These findings suggest that forced running in motor-driven wheel could enhance neurogenesis in the hippocampal DG of adult rats and improve learning ability.

Effects of exercise on neurogenesis in the dentate gyrus and ability of learning and memory after hippocampus lesion in adult rats

Objective To explore the effects of exercise on dentate gyrus (DG) neurogenesis and the ability of learning and memory in hippocampus-lesioned adult rats. Methods Hippocampus lesion was produced by intrahippocampal microinjection of kainic acid (KA). Bromodeoxyuridine (BrdU) was used to label dividing cells. Y maze test was used to evaluate the ability of learning and memory. Exercise was conducted in the form of forced running in a motor-driven running wheel. The speed of wheel revolution was regulated at 3 kinds of intensity: lightly running, moderately running, or heavily running. Results Hippocampus lesion could increase the number of BrdU-labeled DG cells, moderately running after lesion could further enhance the number of BrdU-labeled cells and decrease the error number (EN) in Y maze test, while neither lightly running, nor heavily running had such effects. There was a negative correlation between the number of DG BrdU-labeled cells and the EN in the Y maze test after running. Conclusion Moderate exercise could enhance the DG neurogenesis and ameliorate the ability of learning and memory in hippocampus-lesioned rats.

Analgesic effect of endomorphin-1

AIM

To study the analgesic effect of endomorphin-1 (EM-1).

METHODS

The experiment was performed in rats and mice to study the analgesic effect of intraperitoneal (ip) injection of EM-1 with tail stimulation-vocalization test, writhing test, adjuvant arthritis, and neuropathic pain model and to compare it with the analgesic effects produced by intracerebroventricular (icv) and intrathecal (it) administrations.

RESULTS

1) EM-1 raised the pain threshold dose-dependently in tail stimulation-vocalization test in rats and inhibited the writhing responses induced by ip acetic acid in mice. EM-1 also decreased the hyperalgesia in both adjuvant arthritis and neuropathic pain model. 2) The analgesic effect induced by central (icv and it) administration of EM-1 was faster and more powerful than that induced by peripheral (ip) administration. 3) The analgesic effect of EM-1 was reversed by naloxone (opioid receptor antagonist), as well as by cyprodime (mu-opioid receptor selective antagonist). Repeated administrations of EM-1 induced tolerance.

CONCLUSION

EM-1 had a definite analgesic effect and the analgesic effect of EM-1 was mediated by central mu-opioid receptor.