Observation on the ultrastructure of ependyma in the central canal of 12 rat spinal cords by means of transmission and scanning electron microscope showed that the ependyma is composed of ependymal cells, tanycytes and neurons. The ependymal cells are columnar or cubic in shape. Their apical surfaces are provided with microvilli and cilia which may contact with Reissner's fiber. Neighbouring cells are connected by zonula adherens or zonula occludens. The cytoplasm contains numerous mitochondria and vesicles. Elongated tanycytes situate between ependymal cells. They are provided with microvilli (but no cilia) at apical surfaces. The basal processes thrust into the grey matter, where they inclose capillaries. Abundant microfilaments and microtubes are embedded in the cytoplasm. This paper reports the cerebrospinal fluid-contacting neurons existing in the ependyma of rat spinal cord for the first time. These belong to supraependymal or hypoendymal neurons with small, multipolarcell bodies. Their dendrites and axons could be found in the lumen of central canal. Occasionally, the contact between axon terminal and dendrite was encountered. Morphological evidence mentioned above suggests that ependyma may perform receptive, absorptive and secretory function.

Crest synapses of the substantia gelatinosa have been observed in rat spinal cord by means of electron microscopy. They associate with axe-dendritic or dendrodendritic junctions in this study. The postsynaptic elements come from clubbed finger-like dendritic crest which is characterized by prominent postsynaptic membrane thickening, subjunctional bodies and longer active zone. Two presynaptic terminals contact the wall of crest process side by side and contain complex vesicles: spheric vesicles (40～60 nm in diameter), flat vesicles (75?25 nm), medium-sized granular vesicles (about 70 nm) and large granular vesicles (about 125 nm).Crest synapses differ from spine synapses with respect to that they typically contain two junctions, one on each side of the middle part of the crest and that the postsynaptic boutons are always provided with sub junctional bodies.

Somatostatin-containing neurons and nerve fibers in the commissural subnucleus of the nucleus tractus solitarii(NTS) of the rat were studied by means of munoelectron microscopy. The results showed that somatostatin-like immunoreactive positive neurons are medium or small cells, fusiform or elliptical. Somatostatin- like immunoreactive positive axons are unmyelinated,and mainly form passage or terminal synapses. Somatostatin-positive cell bodies themselves have not been obser- ved to form synapses with somatostatin-positive fibers,but their dendrites may receive innervation from immunoreactive-negative fibers by axo-dendritic synapses.

Objective To explore the regulating mechanism of the astrocytes on the expression of ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors(AMPARs) subunit in epileptogenesis. Methods The astrocytic conditional medium(ACM) was collected after being stimulated by glutamate,and then ACM was added to the cultured hippocampal neurons.The expression changes of neuronal GluR2 and protein interacting with C-kinase-1(PICK1) mRNA were detected by RT-PCR. Results In the cultured hippocampal neurons,the GluR2 mRNA expression was significantly decreased at the 2nd,8(th),and 12(th) hours after the administration of ACM compared with that in the control group(P

The chemical nature of spinal ganglionic neurons, the peripheral processes of which project divergently to the somatic and visceral areas, has been identified by means of tri-labeling method of combining fluorescein tracing and immunocytochemistry. Ten rats were used. First, 2?l of 2% fast blue (FB) were injected into the left coeliac ganglion. Two days later, 2% nuclear yellow (NY) was injected into left 9-11th intercostal nerves(l?l for each). On the 4th day, animal was perfused with 10% formalin in 0.1mol/L phosphate buffer.The left Th9-11 spinal ganglia were removed and cut into sections by cryostat. The sections were observed under fluorescence microscope and photographed. The results showed that there were three kinds of neurons in the spinal ganglia: (1) single FB labeled cells with blue fluorescent cytoplasm accounted for 38.8% of total labeled cells; (2) single NY labeled cells with yellow fluorescent nuclei accounted for 52,7%; (3) FB and NY double labeled cells accounted for 8.5% and mostly were small or medium in size. Then, the double labeled cells-containing sections were further processed by substance P-demonstrating PAP immunocytochemical staining. The immunostain and fluorescent photographs in the same section were compared and identified each other. We have found that the labeling ratio of SP/NY was 1.4%; SP/FB was 7% and SP/NY+FB was 28.8%. Present study has not only identified the convergence of somato-vesceral sensation in spinal ganglia but also detected the chemical nature of these neurons(substance P) for the first time. In addition, this result has provided a morphological basis for the mechanisma of referred pain and somato-visceral reflection.

Skin-visceral divergent projections of cholecystokinin(CCK)-containing dorsal root ganglion neurons were studied by combined technique of fluorescent double-labelling and immunohistochemistry. Fast Blue(FB) and Nuclear Yellow (NY) were injected into the coeliac ganglion and the cutaneous branches of left 9th-11th intercostal nerves, respectively. Three kinds of neurons labelled with fluorescein were observed in T_(9-11) dorsal root ganglia under Nikon fluorescence microscope with 365 nm excitation light: FB-labelled neurons with blue-fluorescing cytoplasm; NY-labelled neurons with yellow-fluorescing nucleus and double-labelled neurons with blue cytoplasm and yellow nucleus. The double-labelled neurons were found to be 2.8％ of total labelled neurons.The sections containing fluorescein labelled neurons were then stained by CCKimmunohistochemical procedure. Four kinds of neurons could be identified: NY-neurons, with CCK-immunoreactivity (NY+CCK); FB-neurons with CCK-immunoreactivity(FB + CCK);NY + FB neurons with CCK-immunoreactivity(NY + FB + CCK); Single CCK-positive neurons. NY + FB + CCK triple-labelled neurons accounted for approximately 11.5％ of NY + FB double-labelled neurons,and 0.4％ of all CCK-positive neurons.The findings clearly indicated that the peripheral processes of some sensory dorsal root ganglion neurons project divergently to both skin and visceral structure, and contain CCK. The present results suggest that the peripheral dichotomization of the dorsal root ganglion nearons might converge sensory inputs from both skin and visceral fields, and thus not only provide one of the structural basis for the referred pain but also reveal that CCK might play a mediation role in the skin-visceral reflection and referred pain.

Projections from substance P (SP)-and cholecystokinin (CCK) containing neurons in the periaqueductal gray(PAG)and Edinger-Westphal(E-W)nucleus to the spinal cord were studied by means of the combining method of HRP tracing with immunocytochemistry in rats. The results showed that a few neurons in the ventrolateral region of PAG projected bilaterally to the cervical, thoracic and lumbar segments of the spinal cord, with the predominant projections from the ipsilateral side. The authors reported that these descending projection neurons showed SP-like immunoreactivity for the first time(account for 48%). The neurons of E-W nucleus projected diffusely to all segments of the spinal cord contained SP (70%) or CCK (73%) respectively, suggesting that at least a part of E-W neurons projecting to the spinal cord contain both SP and CCK.

The distribution of GABA-containing neurons in the anterior horn of L_(4～5) segments of rat spinal cord and their relationship with somatic efferent were studied by combined method of HRP and immunocytochemistry and immunoelectron microscopic method. The results showed that under light microscope, the GABA-immunoreactive cell bodies and terminals were seen in all layers of the anterior horn including Rexed′s layer IX which located in the anterolateral part of the anterior horn. The GABA-positive neurons had round or triangle cell body with many processes and could be divided into two (large and medium) types. Under electron microscope, GABA-immunoreactive products appeared as small granular deposits located in perikarya, dendrite and axon. In axon terminals the immunoreactive products located at periphery of the synaptic vesicles and on the outer membrane of the mitochondria. The GABA-positive dendrites received symmetrical afferent synapses from GABA-positive or negative axon terminals. The combined method of HRP and immunocytochemistry showed that in Rexed′s layer IX there were HRP single labeled neurons, GABA single labeled neurons and HRP/GABA double labeled neurons. The double labeled neurons accounted for 79% of total HRP labeled cells. Above mentioned results first identified the neurons in Rexed′s layer IX of the anterior horn contain GABA which participate in somatic efferent and receive autoregulation from GABA-neurons and nonGABA-neurons at synaptic level.

The divergent projections in the bulbo-cerebellar system of rats were studied by double fluorescein labeling method. 2 ?1 of 2％ Fast blue (FB)were injected into the cerebellar cortex of left anterior lobe, 32 hours later, 2 ?l of 2％ Nuclear yellow (NY)were injected into the cerebellar cortex of right anteior lobe. The animals were allowed to survive 16 hours thereafter. Intracardiac perfusion were performed with 10％ formalin in 0.1 mol/L phosphate buffer. The cerebellum and medulla oblongata were removed and serial sections at 20 ?m were cut by cryostat. One of every two sections was preserved for fluorescence microscopic observation. The results identified that there was no intereonnection between the anterior lobes of two cerebellar hemispheres and the anterior lobe of cerebellum received afferent projections from much more nuclei of the medulla oblongata than previous description. The FB or NY single labeled and FB/NY double labeled cells were observed in the nucleus reticularis lateralis, subnucleus reticularis ventralis, nucleus raphe obscurus, nucleus prepositus hypoglossi, nucleus cuneatus lateralis, nucleus spinalis nervi trigemini and nucleus olivaris aceessorius dorsalis. The double labeled cells accounted for 23％ of total labeled cells except the nucleus olivaris inferior. The results mentioned above suggested that the cerebellum receive multiple afferent connections originated from the medulla oblongata, and the divergent projections further amplify the information-receiving areas in the cerebellum, and synchronize the activities of both cerebellar hemispheres.

In order to clarify the regulatory mechanism of the neurohormone releasing in the neurohypophysis, the immunohistochemical and chemical lesion method were combined to demonstrate the vasopressin (VP)-and catecholamine (CA)-containing nerve terminals, and their distribution and relationship were observed under electron microscopic level. The results showed that in the rat neurohypophysis there were not only widely distributed VP nerve terminals, but also there were many 6-OHDA induced degenerated nerve endings. The close relationship even synapse-like contacts existed between the CA-ergic endings and pituicytes as well as microglial cells. It was very interesting that the CA-ergic boutons formed axoaxonic synapses with VP-containing boutons. In this case, the CA-bouton was presynaptic element whereas the VP-bouton served as postsynaptic element. The above mentioned results probably provided ultrastructural evidence for the regulatory mechanism of the neurohormone releasing in the neurohypophysis for the first time.