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EFFECTS OF CORTICOTROPIN RELEASING FACTOR ON LEARNING AND MEMORY IN THE NUCLEUS BASALIS OF MEYNERT IN RATS

Boning YANG ; Guohe TAN ; Li WEI ; Ling LAN

Chinese Journal of Neuroanatomy.2005;21(5):503-506.

The present study was performed to explore the role of corticotropin releasing factor (CRF) in the nucleus basalis of Meynert (NBM) in spatial learning and memory of rats. The latency, distance and swimming path to find the platform were measured by Morris water maze after intra-NBM injections of 0, 0.01, 0.1 and 0.4 nmol of CRF. Intra-NBM injections of 0.1 or 0.4 nmol of CRF induced significant increase of the latency for spatial learning and memory, and there were no significant changes in the swimming speed in Morris water maze test. The results suggest that CRF plays an inhibitory role in spatial learning and memory consolidation in the NBM of rats.

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pCREB IN GLUTAMATE CONTAINING NEURONS GREATLY UPREGULATED IN RAT AMYGDALA AFTER A STRESS BY FORCED SWIMMING

Lu GAO ; Ruixi LI ; Jie WANG ; Zhongliang DING ; Yuwen PENG

Chinese Journal of Neuroanatomy.2005;21(5):463-470.

Amygdala (AM) plays crucial roles in emotional learning, memory and behavior. These functions of AM are carried out by three main subnuclei (lateral nucleus, basolateral nucleus and central nucleus) in AM and closely related with a transcription factor, cAMP- responsive element binding protein (CREB) in the neurons of the AM. CREB can be phosphorylated (pCREB) in many kinds of neuronal processes to regulate the synthesis of proteins for the formation of memory processes. In order to identify what neuronal types express pCREB and how the pCREB levels changed at different time intervals after an emotional stress stimulation, the present study is designed to investigate pCREB-, glutamate (Glu)- and parvalbumin (PV)- immunoreactive (IR) profiles in AM and the levels of pCREB in AM after a stress of forced swimming (FS). The results showed that the pCREB expressed in the Glu-IR neurons but not in the PV-IR neurons, and the expression level of the pCREB increased dramatically after the stress. The present results suggested that pCREB modulates the emotional processes through the Glu-IR neurons and that the pCREB greatly upregulated to response to the emotional stimuli.

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EFFECTS OF NERVE INJURY ON THE EXPRESSION OF Trk RECEPTOR PROTEINS LOCALIZED ON THE TRIGEMINAL MESENCEPHALIC NEURONS

Fuxing ZHANG ; Yulin DONG ; Feng GUO ; Youwang PANG ; Jinlian LI

Chinese Journal of Neuroanatomy.2005;21(6):625-630.

Immunofluorescence histochemistry combined with retrograde tracing technique was employed to observe the effects of masseteric nerve transection on the expression of Trk ( tropomyosin-related kinase) receptor proteins, namely TrkA, TrkB and TrkC in the trigeminal mesencephalic nucleus ( Me5 ) of the rat. At 7 and 14 days following transection of masseteric nerve through which Fluorogold (FG) was applied to identify the Me5 neurons innervating masseter, brain sections were immunohistochemically processed to detect the three Trk isoforms in FG-labeled Me5 neurons. With the percentage of double-labeled neurons to the total number of FG-labeled neurons as the index,we demonstrated ( 1 ) a significant increase in the percentage of TrkA-immunoreactive (IR) Me5 neurons at both 7 and 14 days after nerve transection, (2) no significant, but gradual, increase in the percentage of TrkB-IR Me5 neruons with longer survival time post transection and ( 3 ) little change of TrkC expression. The current findings indicate that axotomy differently affected the expression of the individual Trk receptors and these expression patterns may reflect an adaptation of the Me5 neurons to the peripheral nerve injury.

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HIGH CONCENTRATION OF IRON IN CEREBROSPINAL FLUID OF RATS INDUCES ALZHEIMER-LIKE BEHAVIORAL AND PATHOLOGICAL CHANGES

Lin LI ; Jianliang WU ; Zheng JIN ; Yan DOU

Chinese Journal of Neuroanatomy.2005;21(3):252-258.

In order to estimate the relationship between iron and the Alzheimer's disease, the behavioral and pathological changes were observed by Morris water maze and immunohistochemical staining respectively after injecting FeC13 into brain ventricle of rats. The apoptosis was tested by flow cytometry and the electron microscopy was used to observe ultrastructural changes. There were significant differences in escape latency of time and distance between normal animals and iron treated rats. Percentage and fluorescence intension (FI) of AnnexinV FITC loaded cells undergoing apoptosis were higher in iron treated rats compared with normal animals. Fawn-coloured products of β amyloid protein were interspersedly distributed in extensive areas of cerebral cortex and hippocampus. Under electron microscope, vacuolate degeneration of neuronal processes with mitochondria degeneration and accumulation of microtubule near vacuolar nucleus were observed in iron treated rats. These results suggest that a local higher concentration of iron in brain may induce Alzheimer-like impairment of intelligence and pathological changes.

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ENDOMORPHIN-1 IS MORE POTENT THAN ENDOMORPHIN-2 IN INHIBITION OF SYNAPTIC TRANSMISSION IN SUBSTANTIA GELATINOSA OF ADULT RAT SPINAL CORD

Dongni LENG ; Yupeng FENG ; Yunqing LI

Chinese Journal of Neuroanatomy.2005;21(3):269-275.

Effects of endomorphin-1 (EM-1) and endomorphin-2 (EM-2) on synaptic transmission were investigated on neurons in substantia gelatinosa (SG) of the spinal dorsal horn by whole-cell voltage clamp recording. Both EM-1 (1 μmol/L) and EM-2 (1 μmol/L)remarkably reduced the frequency but not the amplitude of miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs). These effects were antagonized by 3-funaltrexamine ( β-FNA, 10 μmol/L), a selective μ-opioid receptor antagonist. Noticeably, EM-1 showed higher potency in decreasing the frequency of mEPSCs and mIPSCs than that of EM-2. These results indicate that EMs suppress both excitatory and inhibitory synaptic transmission by activating presynaptic μ-opioid receptors in the SG and EM-1, compared with EM-2, might be a more potent endogenous analgesic at the spinal cord level.

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HYPOXIA INDUCED EXPRESSION OF FOS IN THE DISTAL CEREBROSPINAL FLUID CONTACTING NEURONS IN THE DORSAL RAPHE NUCLEUS OF THE RAT

Zhijun ZHANG ; Hengjian NI ; Zhixian HE ; Xuefeng YANG ; Yan HU ; Huijun XU

Chinese Journal of Neuroanatomy.2005;21(4):360-364.

The effects of hypoxia on the expression of Fos was studied in the distal cerebrospinal fluid contacting neurons (CSF-CNs) in the dorsal raphe nucleus (DR) of the rat. The hypoxic models mimic 8000 m high level were established in a high-altitude decompression chamber. Injecting the tracer of CB ( chorela toxin B subunit) into the rat's lateral ventricles, we investigated the distribution of the distal CSF-CNs in the DR. The single and double immunohistochemistry staining with antibodies to Fos and CB were used to observe the expression of Fos in the distal CSF-CNs in the DR. The results showed that a large number of CB-like immunoreactive (-LI) neurons (31.16 ±3.36/per section) were located in the DR. In hypoxic experimental rats, the number of Fos-LI neurons was increased sharply (40.28 ±2.17/per section, P ＜0.05 compared to control rats), and a few CB/Fos-LI neurons (2.00 ±0.39/per section) could be observed in the DR. In control rats, several Fos-LI neurons (5.55 ±0.81/per section) and no CB/Fos-LI neuron could be observed in the DR. These results suggest that some of the distal CSF-CNs in the DR may play roles in transmitting information between brain and cerebrospinal fluid and modulating the function of brain following hypoxic stimulation.

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ISOLATION OF NEURAL STEM CELLS FROM NEONATAL RAT HIPPOCAMPUS AND THEIR IN VITRO DIFFERENTIATION INTO CHOLINERGIC NEURONS

Xiangying LUO ; Zhimin YANG ; Xiaobin SONG ; Su LIU ; Kuangyan ZHAO ; Zhongtang FENG ; Tinghua WANG

Chinese Journal of Neuroanatomy.2005;21(2):190-194.

The present study aims to isolate neural stem cells from neonatal rat hippocampus and induce them to differentiate into cholinergic neurons. A multipotent cell line derived from the hippocampi of neonatal rats which had the ability to form clones was incubated in serum-free DMEM/F12 medium added with 20ng/ml basic fibroblast growth factor (bFGF) and B27. After differentiation of the neural stem cells, immunocytochemistry was used to detect nestin, the antigen of the cell clone, and β-tubulin (Tuj 1 ), glial fibrillary acidic protein (GFAP) and galactocerebroside (Galc), the markers specific for neurons, astrocytes and oligodendrocytes, respectively. Embryonic chick skeletal muscle extract was used to induce the differentiation of the neural stem cells into cholinergic neurons. The results showed that the cell line isolated from the hippocampi of neonatal rats expressed nestin and had the potential to form clones and differentiate into neurons, astrocytes and oligodendrocytes. Embryonic chick skeletal muscle extract can induce 9.6% of the isolated cell line to differentiate into cholinergic neurons compared with 3.9% in controls. These findings suggested that the cell line, which expressed nestin antigen, was a multipotent cell line capable of self-renewing, and was believed to contain stem cells of the CNS. These neural stem cells can be induced to differentiate into cholinergic neurons by using embryonic chick skeletal muscle extract.

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INVOLVEMENT OF SPINAL ENDOMORPHIN 2 IN MIRROR-IMAGE PAIN INDUCED BY PERIPHERAL INFLAMMATION

Xuezhe HAN ; Huili LI ; Zhiming WANG ; Yunqing LI

Chinese Journal of Neuroanatomy.2005;21(3):299-304.

The present investigation was designed to study, whether endogenous antinociceptive system is effective on mirror-image pain induced by peripheral inflammation. After Complete Freund's adjuvant (CFA) was subcutaneously injected into one hindpaw, besides heat hyperalgesia and mechanical allodynia from 1 h to 72 h at the injured site, contralateral mechanical allodynia was also induced at 1 h and significantly lasted for 24 h after injection, which was called mirror-image pain. To explore the effects of endogenous antinociceptive system on mirror-image pain, endomorphin (EM) 2 was intrathecally administered at doses of 0.2 μg, 2 μg, 20 μg and EM1 was given at the maximum dose of 20 μg by the same way, respectively, 10 min prior to CFA injection. The present results showed that three doses of EM2could reverse the decreased contralateral mechanical threshold from 48.03 ± 9.07 mN ( pre-treatment with vehicle) to 200.49 ± 53.68mN, 247.63 ± 49.43 mN and 250.57 ± 55.34 mN ( pre-treatments with EM2 ), respectively, but not in a significantly dose-dependent manner. On the other hand, intrathecal pre-treatment with EM1, the contralateral mechanical threshold was 51.24 ± 12.59 mN after CFA injection, which was similar to that pre-treatment with vehicle. It indicates that spinal EM1 did not have remarkable effect on mirror-image pain behavior. The present results provide evidence for that spinal EM2, but not EM1, mainly originated from the endogenous antinociceptive system might play an inhibitory role in mirror-image mechanical allodynia induced by peripheral tissue inflammation.

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ASSOCIATION OF VESTICULAR GLUTAMATE TRANSPORTERS-AND 5-HT-LIKE IMMUNOREACTIVE VARICOSITIES WITH MESENCEPHALIC TRIGEMINAL NUCLEUS NEURONS IN THE RAT

Peng CHEN ; Jinlian LI

Chinese Journal of Neuroanatomy.2005;21(1):10-16.

The possible relationship of vesicular glutamate transporters ( VGluT1 and VGluT2 ) - and 5-HT-like immunoreactive (LI) terminals with mesencephalic trigeminal nucleus (Vme) neurons in the rat was examined by using triple-immunofluorescence histochemistry and double-labeled electron microscopic immunohistochemistry. Under confocal laser-scanning microscope, many neuronal cell bodies of Vme showed phosphate-activated glutaminase (PAG) -LI and the vast majority of them were large pseudounipolar neurons. A considerable number of VGluT1 -LI and VGluT2-LI terminals were widely distributed in Vme, the density of VGluT2-LI terminals was higher than that of VGluT1-LI. 5-HT-LI axonal varicosities had dense distribution in Vme, and some 5-HT-LI terminals also showed immunoreactivity for VGluT2. Some VGluT1-LI, VGluT2-LI, 5-HT-LI and VGluT2/5-HT-LI terminals were frequently observed in close apposition to the cell bodies of Vme neurons showing PAG-LI. Under electron microscope, VGluT1/VGluT2-LI and 5-HT-LI were visualized with silver grains and peroxidase products, respectively. Some terminals in Vme showed both VGluT2- and 5-HT-LI, these dual labeled varicosities usually made asymmetric contact with Vme neurons. Synaptic terminals that showed VGluT1-LI was also observed, but no coexpression of VGluT1 and 5-HT was found in Vme. The present results suggest that in the transmission of the proprioceptive sensory information from the orofacial regions to the higher center, glutamate and 5-HT may play important roles on the regulation of Vme neurons through complicated integration.

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DEVELOPMENTAL ORGANIZATION OF PRIMARY AFFERENT FIBERS IN THE DORSAL HORN OF THE MOUSE LUMBAR SPINAL CORD

Shengxi WU ; Yayun WANG ; Sunon CHEN ; Yunqing LI

Chinese Journal of Neuroanatomy.2004;20(1):27-34.

The present study was designed to examine the morphological pattern of primary afferent projections into the spinal dorsal horn by labeling the lumbar dorsal root ganglia with carbocyanine fluorescent dye DiI in mouse embryos and neonatal pups aged embryonic day 12 to postnatal day 3 (E12-P3). Primary afferent fibers projected into dorsal funiculus at E13, but did not penetrated into gray matter of dorsal horn until E15. The afferent projections became dense and entered the spinal gray matter more deeply at E16 and E17. By E18 the intensity of primary afferent in the deep part of the dorsal horn increased and their branching patterns became more complicated. Some of these primary fibers were also observed to ramify extensively in the superficial laminae. The projection pattern of primary afferent remained unchanged after birth, but the intensity of afferent terminals increased in the superficial laminae. In addition, afferent fiber collaterals that projected into the contralateral dorsal horn were also observed. They were first examined at E16 and mainly originated from the medial and deep part of the dorsal horn. Around birth, the contralateral projections were also found to originate from the lateral part of dorsal horn. Our results indicate that laminar organization of primary afferents in the spinal dorsal horn is established during the late embryonic and early postnatal stages.This organization then undergoes further refinement to match the pattern seen in the adult.

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