An inducible transgenic Cre mouse line for the study of hippocampal development and adult neurogenesis.

The hippocampus is crucial for higher brain functions, such as learning, memory, and emotion. Many diseases like epilepsy and Down's syndrome are associated with abnormalities in early hippocampal development. In addition, adult dentate neurogenesis is thought to be defective in several classes of psychiatric disorders. However, the mechanisms regulating hippocampal development and adult neurogenesis remain unclear. One of the limitations to studying these processes is the scarcity of available specific mouse tools. Here, we report an inducible transgenic Cre mouse line, Frizzled 9-CreER™, in which tamoxifen administration induces Cre recombinant. Our data show that Cre is expressed in the developing hippocampal primordium, confined to the granule cell layer at P20 and further limited to the subgranular zone in the adult dentate gyrus. Cre recombinase shows very high activity in all of these regions. Thus, this transgenic line will be a powerful tool in understanding the mechanisms of hippocampal development, adult neurogenesis, and associated diseases.

Expression of Frizzled10 in mouse central nervous system.

Frizzled transmembrane proteins (Fzd) are receptors of Wnts, and they play key roles during central nervous system (CNS) development in vertebrates. Here we report the expression pattern of Frizzled10 in mouse CNS from embryonic stages to adulthood. Frizzled10 is expressed strongly at embryonic days E8.5 and E9.5 in the neural tube and tail bud. At E10.5, Frizzled10 is expressed in the forebrain vesicle, the fourth ventricle and the dorsal spinal cord. From E12.5 to E16.5, Frizzled10 expression is mainly observed in the cortical hem/fimbria, the neuroepithelium of the third ventricular zone, midbrain, developing cerebellum, and dorsal spinal cord. At P0, with the exception of expression in the fimbria, Frizzled10 mRNA expression is limited to specific nuclei including the ventral posterior thalamic nucleus (VP) and the dorsal lateral geniculate nucleus (DLG) in the developing thalamus as well as in the proliferative ventricular zone of the developing cerebellum. From P20 to adult, Frizzled10 mRNA is detected only in the internal capsule (ic). Our data show that expression of Frizzled10 is very strong during embryonic development of the CNS and suggest that Frizzled10 may play an essential role in spatial and temporal regulation during neural development.

[Mechanism of hypothalamic effect in small intestine electro-activity of rats regulated by fructus aurantii immaturus].

OBJECTIVE: To observe the effect of Fructus Aurantii Immaturus (FAI) on the electro-activity of small intestines in rats, and evaluate the interrelations between the FAI regulating effect and choecystokinin (CCK) and somatostatin (SS). METHODS: Migrating myoelectric complex (MMC) cyclic period, the ratio of the active time to the cyclic period, and the number of the fast wave within the active time per minute were observed between FAI and the normal saline group by external alimentary canal electrodes; the CCK contents in dorsomedial hypothalamic nucleus (DMH), ventromedia hypothalamic nucleus (VMH), lateral hypothalamus area (LHA) and SS in VMH, LHA, paraventricular nucleus (PVN) by using immuno-chemistry technique and micro-image pattern quantitative analysis and scanning system. RESULTS: The MMC cyclic period shortened, the ratio of the active time to the cyclic period increased and the number of the fast wave within the active time per minute increased in the FAI group, which showed significant difference from the normal saline group; CCK positive neurons were reduced in the areas of DMH, VMH and LHA, SS positive neurons were increased in the areas of VMH, LHA and PVN in the FAI gioup,which showed significant difference compared with the normal saline and the blank control group. CONCLUSION: FAI can stimulate the electro-reactivity of small intestines. The stimulative effect of FAI might be related to CCK and SS in hypothamus.

Inducible genetic lineage tracing of cortical hem derived Cajal-Retzius cells reveals novel properties.

During cortical development, Cajal-Retzius (CR) cells are among the earliest-born subclasses of neurons. These enigmatic neurons play an important role in cortical development through their expression of the extracellular protein, reelin. CR cells arise from discrete sources within the telencephalon, including the pallial-subpallial border and the medial (cortical hem) regions of the pallium. Combined evidence suggests that CR cells derived from distinct origins may have different distributions and functions. By tracing CR cells derived from the cortical hem using the inducible Cre transgenic mouse tool, Frizzled 10-CreER™, we examined the specific properties of hem-derived CR cells during cortical development. Our results show that the progenitor zone for later production of CR cells from the hem can be specifically marked as early as embryonic day 6.5 (E6.5), a pre-neural period. Moreover, using our Cre line, we found that some hem-derived CR cells migrated out along the fimbrial radial glial scaffold, which was also derived from the cortical hem, and preferentially settled in the hippocampal marginal zone, which indicated specific roles for hem-derived CR cells in hippocampal development.

[Experimental study on the effect of Glycyrrhiza on small intestinal motility in rats].

AIM: To investigate the effects of glycyrrhiza decoction on migrating myoelectric complex (MMC) and gastrointestinal hormone in small intestine in rats. METHODS: We observed MMC cycle,phase Ill duration,fast wave numbers of phase III of MMC in one minute, fast wave numbers of one cluster in phase III of MMC of small intestine of glycyrrhiza group and control group rats with electrophysiology method, and immunohistochemistry to examine relative content of serotonin (5-HT), substance p(SP) and vasoactive intestinal polypeptide (VIP) in small intestinal chromophil (EC) and myenteric nerve plexus in small intestine of control group and glycyrrhiza group rats. RESULTS: Compared glycyrrhiza group with control group,we found that glycyrrhiza was able to decrease fast wave numbers in one minute and fast wave numbers in one cluster in phase III of MMC of small intestine (P < 0.05), and evidently extend small intestinal cycle of MMC (P < 0.05), it also shortened the phase III III duration (P < 0.05) or made the phase III of MMC absent. Compared glycyrrhiza group with control group it was indicated that content of 5-HT in small intestinal mucous membrane and myenteric nerve plexus was evidently decreased (P < 0.05), and content of SP in myenteric nerve plexus of small intestine of rats was evidently decreased (P < 0.05), and content of VIP in small intestine of rats was evidently increased (P < 0.05). CONCLUSION: Glycyrrhiza is able to inhibit small intestinal motility, this inhibition is related with the amount of 5-HT, SP, VIP secreted by small intestinal mucous membrane of rats.