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Objective To investigate the response of astrocytes and neurons in the medullary visceral zone (MVZ) to neuropathic pain induced by the spared nerve injury (SNI, the tibial nerve and the common peroneal nerve were sectioned, while the sural nerve was intacted). Methods The SNI operation and sham operation (only incised the skin of thigh, but the tibial nerve and the common peroneal nerve did not cut) were performed in adult male Sprague-Dawley rats. The paw withdrawal mechanical threshold (PWMT) was measured at 10,20,30 days after operation. By using single or double immunofluorescent staining method,we investigated and measured that the mean fluorescent intensity (MFI) of anti-glial fibrillary acidic protein (GFAP, a marker of astrocytes) signal in the astrocytes, the mean member of Fos/ GFAP double labeled astrocytes and Fos / tyrosine hydorxylase (TH) double labeled neurons in MVZ after operation. Results As compared with control or sham groups, SNI induced that the PWMT became significant sensitivity and peaked at 20 days after SNI. The activated astrocytes revealed an activated morphology, the MFI of anti-GFAP signal markedly strengthened, the mean number of Fos/GFAP double labeled astrocytes and Fos/TH double labeled neurons in the nucleus of the tract solitarius (NTS) and the ventral lateral medulla (VLM) increased significantly and peaked at 20 days after SNI. Conclusion The neurons and astrocytes in MVZ were sensitively activated by SNI.
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Objective To investigate the effects of electro-acupuncture on gastric emptying and Fos expression in the neuron of vagal-solitary complex (VSC) of rat bulbus after lipopolysaccharide (LPS) intraperitoneal injection (i.p.). Methods 40 male SD rats were randomly assigned to 4 groups: control group, LPS i.p. group, LPS i.p. plus electro-acupuncture at Tsusanli point group and LPS i.p. plus electro-acupuncture at non-meridian-non-acupoint group, 10 rats for each group. Immunohistochemical techniques were used to detect the Fos expression in VSC. The animal's gastric emptying was measured by phenol red method. Results The rats with gastric emptying decreased greatly to (20.7±4.5)% 2.5 hours after LPS injection, and Fos-positive neurons were significantly found in VSC (83.2±6.6) compared with control group. However, in the group of LPS i.p. plus electro-acupuncture at Tsusanli point, the gastric emptying was up-regulated to (44.1±6.2)%, and the expression of Fos -positive neurons were down-regulated to (37.9±3.8) compared with LPS i.p. group. No significant difference was found between the group of LPS i.p. plus electro-acupuncture at non-meridian-non-acupoint and the group of LPS i.p. Conclusion LPS i.p. can retard the gastric motility in rats, electro-acupuncture at Tsusanli point may well regulate the function in LPS model rats. This function may be connected with its protective effects on Fos immunoreactive neurons activity in VSC of rat bulbus.
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BACKGROUND: Astrocytes play active roles in neuronal activity through reciprocal communication with neurons.OBJECTIVE: To observe the distribution of pyramidal cells and astrocytes in rat hippocampal CA3 area and to reconstruct their three-dimensional relationship.DESIGN: A randomized controlled experiment based on rats.SETTING: Neurosurgery department in a university and neuroscience institute in a military medial university of Chinese PLA.MATERIALS: The experiment was conducted in the Neurosurgery Department of Zhujiang Hospital of Southern Medical University and the Neuroscience Institute of Fourth Military Medial University of Chinese PLA from October 2001 to June 2003. Thirty-day-old male SD rats were provided by the Experimental Animal Center of Fourth Military Medial University of Chinese PLA.METHODS: The techniques used in this study were brain slice patch-clamping whole-cell recording, lucifer yellow (LY) staining, immunofluorescence and laser scanning confocal microscopy(LSCM).MAIN OUTCOME MEASURES: The discharge features of neurons and the spatial distribution of astrocytes.RESULTS: The hippocampal neurons were classified into 2 types according to their discharge patterns: phasic and non-phasic neurons. The observation under both LSCM and three-dimensional reconstruction revealed that a large number of astrocytes aggregated around LY-dyed pyramidal cells and there were tight contacts between them. The contacts between astrocytes and the two types of neurons differed in that they were found both on dendrites and cell body of non-phasic neurons but on dendrites of phasic neurons.CONCLUSION: The spatial distributions of astrocytes around different types of hippocampal pyramids may be different.
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BACKGROUND: Lipopolysaccharide(LPS), as a polyclonal immune exciter, can simulate immune excitation status, which is useful in the observation of whether the catecholaminergic neurons in paraventricular nucleus of hypothalamus(PVN) projected from medullary visceral zone(MVZ) react towards LPS stimulation that is to provide a theoretical gist for the researches on the protection of brain function.OBJECTIVE: To observe whether PVN catecholaminergic neurons projected from MVZ react towards LPS stimulation for the exploration of the impacts of MVZ-PVN catecholaminergic access in "immune-to-brain communication".DESIGN: A randomized controlled study using experimental animals as subjects.SETTING: An Institute of Neurosurgery and Neurology of one Military University of Chinese PLA.MATERIALS: The study was conducted in the Department of Neurosurgery of Zhujiang Hospital affiliated to Southern Medical University and the Institute of Neurology of the Fourth Military Medical University of Chinese PLA from January to December in 2002. Ten healthy adult SD rats in cleanness grade were obtained from the experimental animal center of the Fourth Military Medical University of Chinese PLA.METHODS: WGA-HRP was injected into PVN of one side of the rat, and the immune exciter LPS was injected into the abdominal cavity after 48 hours of survival to induce immune response. Samples were stained by triple labels of WGA-HRP method and double immunohistochemical staining of anti-Fos and anti-TH antibodies.MAIN OUTCOME MEASURES: To observe the distributions and expressions of WGA-HRP labeled cells, Fos protein, and catecholaminergic neuron(labeled by TH) in MVZ.RESULTS: Seven immune-reactive(IR) positive neurons were found in MVZ, i. e., HRP, Fos or TH single labeled cells, Fos/HRP, Fos/TH or HRP/TH double labeled cells, and Fos/HRP/TH triple labeled cells. Fos/HRP double labeled neurons and Fos/HRP/TH triple labeled neurons accounted for 12. 5% and 39.6% of HRP labeled cells respectively.CONCLUSION: MVZ reacts to LPS immune stimulation, which could upload the immune message to PVN through Catecholaminergic neurons.MVZ might be a relay station in "immune-to-brain communication", which exerts immune modulatory impact through "MVZ→PVN" access.
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BACKGROUND: It is considered traditionally that epilepsy is a kind of complicated nervous conduct disorder caused by abnormally excited neuron in different area in brain. While the research on the function of astrocyte in epileptic attack is very rare.OBJECTIVE: To study the reaction of neuron and astrocyte in medullary visceral zone after epilepsy induced by pentetrazole in rats.DESIGN: A randomized controlled experimental research.SETTING and MATERIALS: The experiment was done in the Neurosurgery Laboratory of Zhujiang Hospital Affiliated to Southern Medical University and Neuroscience Institute of Fourth Military Medical University of Chinese PLA. Fourteen healthy adult SD rats, weighing 180 - 220 g, clean grade, were provided by the Experimental Animal Center of Fourth Military Medical University of Chinese PLA.INTERVENTIONS: Distribution of neuron and astrocyte in MVZ 1 hour after epileptic attack was shown by laserconfocal microscopic technique combined with triplication immunofluorescence histochemistry of anti-Fos protein, anti-tyrosine hydroxylase(TH) and anti-glial fibrillary acidic protein(GFAP).MAIN OUTCOME MEASURES: Observation of distribution of positive cells of Fos, GFAP and TH in MVZ and relationship between GFAP positive astrocyte and neuron.RESULTS: Fos positive neurons and GFAP positive astrocytes in MVZ increased significantly. Triplication immunofluorescence histochemistry showed reaction neuron(Fos positive) closely related with reaction astrocyte(GFAP positive) . Three kinds of N-ASC compounds with different labels were found, which were TH +/Fos +/GFAP + three labeled compound, TH + /GFAP +/Fos- and Fos+/GFAP +/TH- two labeled compound.CONCLUSION: Neuron and astrocyte in MVZ reacted strongly when epilepsy attacks. N-ASC as a functional unit may regulate onset of epilepsy.
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The cholinergic neurons and fibers of the hypothalamus could not be revealedsuccessfully in the past,therefore,there has been general agreement that the hypotha-lamus is very poorly innervated by cholinergic system.In this study,choline acetyl-trans ferase (ChAT)-like immunoreactive positive neurons and fibers of the hypo-thalamus were revealed successfully by using avidin-biotin immunocytochemical me-thod.This study demonstrated for the first time that the cat hypothalamus is richlyinnervated by cholinergic system.We found cholinergic neurons of varying numbersin the following areas:dorsomedial hypothalamic nucleus,paraventricular nucleus,dorsal hypothalamic area,the area of the tuber cinereum surrounding ventromedialhypothalamic nucleus,lateral hypothalamic area,anterior hypothalamic area,anteriorhypothalamic nucleus,parvocellular hypothalamic nucleus,tuber-mammillary nucl-eus,posterior hypothalamic area,anterior mammillary nucleus and supramammillarynucleus.There were a lot of ChAT-like positive fibers in the lateral hypothalamicarea,mammillary area,dorsal hypothalamic area,paraventricular nucleus,parvocel-lular hypothalamic nucleus,the area of the tuber cinereum.Three kinds of neuronperikarya related to cholinergic system were identified in the hypothalamus of thecat:1.cholinergic perikarya;2.noncholinergic-cholinoceptive perikarya;3.choli-nergic-cholinoceptive perikarya.There were also immunoreactive positive fiberswhich were non-varicose and varicose.Two kinds of varicose-fibers,one withstrong immunoreactivity and the other with weak immunoreactivity were distingui-shed.
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It is demonstrated that the parabigeminal nucleus of the rat is subdivided intodorsal,middle and ventral groups.The parabigeminal nucleus sends fibers to bila-teral superior colliculus,the rostral half of it predominantly projects to the rostralhalf of the contralateral superior colliculus,but the rostral end projects only to thecontralateral one;the caudal half of this nucleus predominantly projects to thecaudal half of the ipsilateral superior colliculus,but the caudal end projects only tothe ipsilateral one.The superficial layer of the superior colliculus receives projec-tions from the ipsilateral dorsal and ventral groups and from the contralateralmiddle group of the parabigeminal nucleus.The middle and deep layers receive pro-jections from the ipsilateral middle group and contralateral dorsal and ventral groups,and probably from the other groups of both sides.The superior colliculus also sends fibers to both parabigeminal nuclei,predo-minantly the ipsilateral side.The lateral tegmental area sends fibers to the middle and deep layers of the su-perior colliculus.From the results described above,it could be concluded that the parabigeminalnucleus——tectum——parabigeminal nucleus connections are not only concerned withsuperficial layer,but also with the middle and deep layers of the superior colliculus.The tegmentum——tectum——tegmentum connections are only concerned with the mid-dle and deep layers of the superior colliculus.
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Objective To observe the influences of electroacupuncture(EA) on the morphological changes in neurons and glia cells in sacral dorsal commissural nucleus(SDCN) of rats with ulcerative colitis(UC),and study the mechanism of acupuncture in modulating central nervous system in UC.Methods Forty-eight male SD rats were randomly assigned to four groups: control group,UC model group,EA Tsusanli group(UC plus EA at Tsusanli acupoint) and EA non-acupoint group(UC plus EA non-acupoint group).According to the acupuncture duration,EA Tsusanli group was divided into three subgroups: 1-day,3-day and 5-day subgroup(8 rats for each subgroup).UC model of rats was reproduced by instillation of a solution containing ethanol and 2,4,6,-trinitrobenzenesulfonic acid(TNBS) into the distal colon.When the treatment was ended,all the rats were sacrificed and SDCN slides were prepared.The expressions of Fos,glial fibrillary acidic protein(GFAP) and OX42 immunoreactivity in SDCN were assessed and calculated by using single or double immunohistochemical methods.Results In the three experimental groups,the Fos-positive neurons,GFAP-positive astrocytes and OX42-positive microglia were mainly expressed in SDCN.In UC model group and EA non-acupoint group,the expressions of Fos,GFAP and OX42 immunoreactivity were stronger than those in EA Tsusanli group(P
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40 ?m in diameter) were accounted for about 15％, and the rest were medium-and small-sized cells.
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In the present study the commissural projection between the two superior colliculi in the rat was examined with horseradish peroxidase method. The result shows that when HRP was injected into the superior colliculus of one side, HRP labeled cells could be found in every part of the contralateral superior colliculus. In each case the labeled cells were relatively concentrated in the region corresponding to the site of injection. It indicates that various parts of one superior colliculus may be connected chiefly with the corresponding part of the opposite side through the commissural projection.Most of the labeled cells were found in the middle layer of the superior colliculus, especially in its upper half, less in the deep layer, and the least in the superficial layer. Neurons in the superficial layer of one side project only to the superficial layer of the contralateral side, and so are the middle-deep layers. The connections between the superficial layers of both sides were independent from those of the middledeep layers.The commissural projection of the bilateral superior colliculi passes through the commissure of the superior colliculus which could be divided into a dorsal and a ventral fiberal fasciculns. The dorsal one was smaller, predominantly related to the superficial layer and the upper half of the middle layer; the ventral one was larger, part of its fibers related to the lower half of the middle layer and the deep layer, while the rest project to other nuclei of the contralateral region of the mesencephalon (e. g. nucleus cuneiforms, etc,).Most of the labeled cells were small in size, the rest were medium-sized, and no large ones were found.
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A cerebellar afferent connection from the periaqueductal grey (PAG) has been demonstrated in the rat by means of retrograde transport of horseradish peroxidase (HRP) in the present study. The projection is bilateral, but the projection from the ipsilateral side is predominant (3:1). Its main origin is the ventromedial and ventrolateral regions of middle and caudal parts of PAG (98.8％), and the fibers reach different cerebellar cortical regions: culmen, declive, folium vermis, tuber vermis, pyramis vermis, uvula vermis, lobulus quadrangularis, crus Ⅰ, crus Ⅱ, and paraflocculus. Most labelled neurons are medium sized, but some small neurons also appear to project to cerebellum. Only a few large neurons are retrogradely labelled at the most caudal end of the caudal part. Functionally, both cerebellum and PAG are related to visceral activities. Consulting the present experiment, we discussed the significant role of the PAG-cerebellar projection.
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In order to study the bifurcate projections of midbrain periaqueductal gray and nucleus raphe dorsalis to nucleus accumbens and nucleus raphe magnus, the fluorescence double-labeled method was used in the present study. Bisbenzimide (Bb) and propidium iodide (PI) were injected into nucleus raphe magnus and unilateral nucleus accumbens stereotaxically according to the time period necessary for their axonal transport. The percentages of double-labeled neurons were 21％; PI single labeled neurons were 32％; Bb single labeled neurons were 47％. Most of the labeled neurons were located in the middle and caudal parts of periaqueductal gray and the nucleus raphe dorsalis, and most were medium sized and fusiform and triangular in shape.
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The distributions of 5-HT-like and Met-ENK-like immunoreactive (5-HT-LI and Met-ENK-LI) structures in the nucleus accumbens (Acb) of rats were studied by immunohistochemical technique in the present study. Under light microscope, 5-HT-LI fibers and terminals could be seen in each subnucleus at different planes of Acb, but the 5-HT-LI fibers and terminals in the medial and ventral subnuclei were more than the dorsal and lateral subnuclei, the amount of 5-HT-LI fibers and terminals in the caudal segment were more than the rostral segment. According to the diameter, pathway, and number of varicosity, 5-HT-LI fibers could be divided into 3 types: (A) thick fiber (0.35—0.40?m); (B) medium fiber(0.20—0.30?m); (C) thin fiber (about 0.10?m). These 3 types of 5-HT-LI fibers were remarkable in the medial and ventral subnuclei of Acb. 5-HT-LI neuronal bodies did not observed in the Acb. A few scattered Met-ENK-LI neuronal bodies were seen in the ventral subncleus and ventral part of the medial subnucleus. Met-ENK-LI fibers and terminals distributed in all subnuclei and predominant in the medial and ventral subnuclei. The distributions of Met-ENK-LI structures were no differences between the rostral and caudal segments. All of the Met-ENK-LI fibers were thin and irregular and villi-like in shape. There were only a few varicosities on the MetENK-LI fibers. Part of Met-ENK-LI fibers looked like discontinued varicosities. Under electron microscope, 5-HT-LI axonal boutons formed symmetric and asymmetric synapses with non-5-HT-LI dendrites. Met-ENK-LI dendrites formed symmetric and asymmetric axo-dendritc synapses with non-Met-ENK-LI axonal boutons. These synapses were mainly observed in the medial and ventral subnuclei of Acb. The identity of 5-HT-LI and Met-ENK-LI structures, especially in the medial and ventral subnuclei, supported the physiological studies that 5-HT-LI ascending efferent fibers activated the Met-ENK-LI neurons and then the latter sent descending efferent fibers to lower brainstem structures to take part in antinociceptive functions.
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The projections from the nucleus tractus solitarii (NTS) and the nuclei parabrachiales (PB) to the nucleus accumbens (Acc) in the rat have been visulized using anterograde and retrograde HRP tracing techniques. After injecting HRP into the Acc, retrogradely labelled neurons were observed in bilateral PB and NTS with ipsilateral predominance. The labelled neurons were concentrated in the following areas of the PB and NTS: the waist area of the caudal PB, the external subnucleus and other part of the nucleus medialis parabrachialis (PBm), the external, central, and internal subnuclei of the nucleus lateralis parabrachialis (PB1) and the medial subnucleus of the caudal NTS (NTSm). After injecting HRP into the NTSm and commissural nucleus of the NTS, anterogradely labelled terminals were found bilaterally in the PBm and the ventral 3/4 area of the PB1. The densest sites occupied the waist area, the external, central, and internal subnuclei of the PB1. The density of the labelled terminals on the ipsilateral side was little higher than that on the contralateral side. The results indicate that there are two possible pathways from the NTS to the Acc, the one is the direct projection from the medial subnucleus of the caudal NTS to the Ace, the other is an indirect one, i. e. from the medial subnucleus and commissural nucleus of the caudal NTS to the waist area of the caudal PB, the external subnucleus, the dorsal part of the PBm, the external, central, and internal subnuclei of the PB1, where the NTS projection is. presumed to be relayed, and then, project from the PB to the Acc. This connection may be involved in the neural regulation of visceral and locomotor activities.
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By using of combined HRP retrograde tracing and immunocytoche mistry methods, the projection from the caudal part of the ventrolateral medulla (VLM) to the nucleus accumbens (Acb) was examined. When HRP was injected into the ventral and medial area of the caudal part of Acb, the labeled cell bodies were mostly found in the bilateral (predominantly ipsilateral) caudal part of the VLM. When HRP technique (HRP injected into the Acb)was combined with immunocytochemical method, many HRP-TH, HRP-NT and HRP-CCK double labeled cell bodies were found in the VLM. The number of the HRP-TH double labeled cell bodies were numerous, while HRP-NT and HRP-CCK doublelabeled cells were less. HRP-TH double labeled neurons were also found in the reticular formation between the solitary tract nucleus and VLM.
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The projection from the nucleus of solitary tract (Sol) to the nucleus accumbens (Acb) was examined by using HRP retrograde and anterograde tracing combined with immunocytochemical double-labeling technique. The following results were obtained: (1) when WGA-HRP was injected into the caudal part of the Sol, the labeled fibers, terminals and cell bodies were found in the ventromedial area of the caudal Acb. After injecting HRP into the ventromedial area of the caudal Acb, labeled cell bodies and terminals were found in the ipsilateral and contralateral caudal part of the Sol,mainly in the commissure nucleus and the medial subnucleus of nucleus of solitary tract. (2) After injecting HRP into the Acb and combined with immunocytochemical method, many HRP-TH, HRP-NT, and HRP-CCK double-labeled cell bodies were found in the caudal part of the Sol. The number of the HRP-TH double-labeled cell bodies was most numerous, HRP-NT cells was next and HRP-CCK cells was even less.
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5-HT-, SP- and L-ENK-like (5-HT-LI, SP-LI and L-ENK-LI) immunoreactive ultrastructures of the ventrolateral subdivision (VLS) of midbrain periaqueductal gray (PAG) in the rat were observed by immunoelectron microscopical technique in the present study. 5-HT-LI neuronal cell bodies were frequently seen in the VLS of the PAG. 5-HT-LI dendrites were found to form axo-dendritic synapses with non-immunoreactive axon terminals, and the major form of this kind of synapse was asymmetric. A few 5-HT-LI axon terminals formed axo-axonic synapses with non-5-HT-LI axon boutons. 5-HT-LI and non-5-HT-LI axon boutons formed axo-dendritic and axo-somatic synapses with 5-HT-LI dendrites, non-5-HT dendrites and 5-HT-LI neuronal cell bodies, respectively. SP-LI fusiform neuronal cell bodies were only a few and formed axo-somatic synapses with non-SP-LI synaptic boutons which contained pleomorphic vesicles. SP-LI dendrites formed axo-dendritic synapses with non-SP-LI axon terminals, this kind of synapse was the main form of synapses formed by SP-LI structures. SP-LI axon boutons formed axo-somatic and axo-dendritic synapses with non-SP-LI neuronal cell bodies and SP-LI dendrites. L-ENK-LI neuronal cell bodies were also limited. The most common form of synapses of L-ENK-LI structures was L-ENK-LI dendrites formed axo-dendritic synapses with non-L-ENK axon terminals. Non-L-ENK-LI axon terminals constituted axo-somatic synapses with L-ENK-LI neuronal cell bodies. A few L-ENK-LI axon terminals formedaxo-dendritic synapses with L-ENK-LI dendrites. The majority of the synapses mentioned above contained spherical clear vesicles, but some were mixed with a few flat, oval and granular vesicles. The immunoreacrive products were located on the surface of vesicles or on the surface of membranous organelles in the cytoplasm.
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The ultrastructure of the rat nucleus raphe magnus (NRM) was observed under transmission electron microscope in the present study. Most of the neurons of the NRM were medium and small sized fusiform and triangular in shape, they had spherical or ellipsoid nuclei and rather high nucleo-cytoplasmic ratio. Nuclear rodlets which composed of parallel filaments could be seen in some fusiform NRM neurons. There were numerous organelles in the cytoplasm. Axonal terminals apposed to most neuronal bodies and formed axo-somatic synapses. The predominant type of these synapses was symmetric. Sometimes, rod-like or spine-like cytoplasmic protrusions could be seen on the neuronal bodies, they often made axo-somatic synapses with axonal terminals. The neuropil of the NRM was quite complex. It was formed by transverse sections of myelinated fibers, unmyelinated fibers, synapses, and neuroglia. The axo-dendritic synapses were the major synaptic type in the neuropil. The predominant type of these axo-dendritic synapses was also symmetric and asymmetric axo-dendritic synapses. Some axonal terminals were arranged parallel with dendrites and formed symmetric synapses. Beneath subsynaptic membrane of some postsynaptic bags, there were some electrical dense spherules or bands which formed subsynaptic dense bodies. There were. no typical axo-axonic synapses in the NRM, but the parallelly arranged axonal terminals were often seen. Most of the presynaptic bags contained clear spherical vesicles or mixed with flattened and granular vesicles. Some postsynaptic bags were filled with flattened vesicles, they were also often mixed with spherical and granular vesicles.
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The submicroscopic structure of nucleus accumbens (Acb) was observed under transmission electron micrscope in the present study. Most of the Acb neurons were spherical, with diameter ranging from 10 ?m to 15 ?m. The nucleus were ellipsoid with, sometimes, nucleolus and deep invaginations of nuclear membrane. The nucleocytoplasmic ratio was always rather high. Axo-somatic synapses were formed on the surface of most neuronal perikarya, predominantly of the symmetric type. The percentage of axo-somatic synapses in total number of Acb synapses was 2%. Generally, the outline of the dendrites was regular. Most of the thick dendrites made symmetric axo-dendritic synapses while the thin dendrites usually made asymmetric axo-dendritic synapses. Some of the irregular dendrites had spines. The spines were usually long and thin, with enlarged end and markedly thin neck, and formed asymmetric synapses with axonal terminals. The axo-dendritic synapes composed 97% of the total synapses within Acb. Small sized axons were frequently observed. The majority of the axon terminal segments contained clear round vesicles and made synapses en passant with the dendrites. Synapses en passant were also observed on the collaterals of axon. Two or more axonal terminals were often closely contacted, but no typical synaptic formations were found. Only a few axo-axonic synapses could be observed. Axoaxonic-dendritic synaptic complexes were also seen. The percentage of axo-axonic synapse was 0.5%. Most of the synaptic boutons mentioned above were mainly filled by spherical vesicles, some of them were filled with pleomorphic vesicles.
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The transmission electron microscopic technique was used in the present study to observe the normal ultrastructure of the ventrolateral subdivision (VLS) of the rat midbrain periaqueductal gray (PAG). Most of the neurons in the VLS of PAG had medium-sized fusiform neuronal cell body, ellipsoid nucleus and irregular nuclear membrane with deep invaginations or infoldings. The nucleolus was electron dense, large and spheroidal. There were many kinds of organelles in the cytoplasm and the Golgi apparatus in some cells were circular or semicircular. The percentage of axo-somatic synapse in total synapses in VLS was 6% and most of them was of symmetric type (82%). Axo-dendritic synapses counted 94%, of these 66% were symmetric type, 34% were asymmetric. Some special types of axo-dendritic synapse were observed. e. g., axo-spine synapse, parallel synapse, and central dendritic synaptic glomerulus. The synaptic vesicles in the presynaptic bags of the synapses mentioned above were mainly clear spherical in type, and most of the clear spherical vesicle-filled bags contained a few flattened vesicles and granular vesicles. Only a few bags were mainly filled with flattened vesicles.