ABSTRACT
After injecting retrograde tracer fiuoro-gold (FG) into the parabrachial region(PB), caudal ventrolateral medulla(CVLM) and the fourth segment of cervical spinal cord (C4), respectively, neurons in laminae I ～ Ⅱ of the medullary dorsalhorn projecting to the above mentioned brain areas were observed. PB received projections from bilateral laminae I and Ⅱ withan ipsilateral dominance; CVLM and C4 received projections from ipsilateral laminae I and Ⅱ. Neurons projecting to C4 werevery sparsely distributed in laminae I and Ⅱ of the medullary dorsal horn. The projecting neurons in outer part of lamina Ⅱwere more than those in inner part of lamina Ⅱ . Combined with immunofluorescence histochemistry for calbindin-D28k(CB) andparvalbumin(PV), it was demonstrated that a part of neurons projecting to PB or CVLM showed CB-like immunoreactivity, butnone of them exhibited PV-like immunoreactivity. There were only a few neurons in lamina Ⅱ projecting to C4 and they exhibitedneither CB- nor PV-like immunoreactivity. The present study provides further evidence for the existence of projecting neurons inlamina Ⅱ and suggests that immunostaining against CB and PV may distinguish two neuronal subpopulations in lamina Ⅱ .
ABSTRACT
Immunoelectron microscopic technique was used in the present study to observe the serotonin (5-HT)-, substance P (SP)-, and leucine-enkephalin (L-Enk)-like immunoreactive ultrastructures in the nucleus raphe magnus (NRM) of the rat. 5HT-like immunoreactive (5-HT-LI) axonal terminals were found to form axosomatic, axo-dendritic, and axo-axonic synapses with non-5-HT-LI neuronal cell bodies, 5-HT-LI and non-5-HT-LI dendrites, and non-5-HT-LI axonal terminals respectively. Non-5-HT-LI axonal terminals formed axo-somatic and axo-dendritic synapses with 5-HT-LI neuronal cell bodies and dendrites. SP-LI (or L-Enk-LI) axonal terminals formed axo-somatic, axo-dendritic synapses with SP-LI (or L-Enk-LI) and non-SP-LI (or non-L-Enk-LI) neuronal cell bodies and dendrites, respectively. L-Enk-LI axonal terminals constituting axo-axonic synapses with L-Enk-LI axonal boutons were observed less frequently. The most common synaptic type made by 3 kinds immunoreactive profiles mentioned above was axo-dendritic synapses made by non-immunoreactive axonal terminals with immunoreactive dendrites. The majority of the immunoreactive axonal boutons were mainly filled by clear spherical vesicles, but sometimes were mixed with small number of flat and granular vesicles. The immunoreactive products were irregular electron-dense substances, and were located on both inner and outer surfaces of the vesicles, or on the surface of the membranous cell organelles in the cytoplasm, etc.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
The projections of diencephalon onto the rostral part of the mesencephalic periaqueductal gray matter (PAG) were investigated by using the method of retrograde transport of HRP in the rat. The results have led to following conclusions:1. The diencephalic afferents to the rostral part of PAG originate mainly from medial preoptic area, anterior hypothalamic area, dorsomedial and ventromedial hypothalamic nuclei, dorsal premamillary nucleus, lateral hypothalamic region, Forel's field and zona incerta ipsilaterally, and a few of them originate contralaterally.2. The anterior hypothalamic area, ventromedial hypothalamic nucleus, dorsal premamillary nucleus and zona incerta project more to the ipsilateral nucleus: lateralis of PAG than to the nucleus medialis and contralateral nucleus lateralis of PAG.3. In the anterior hypothalamic area, a large number of neurons projecting to PAG was located in the lateral anterior nucleus.4. In the lateral hypothalamic region, the lateral preoptic area and anterior division project to both nuclei lateralis and medialis, while its tuberal and mamillary divisions probably project only to nucleus lateralis.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
WGA-HRP was injected into the inferior colliculus in the rat in order to study the non-auditorial afferents of the inferior colliculus. In the diencephalon and truncus encephali, retrograde labeling was observed in many non-auditorial regions: bilateral (with contralateral predominance) cuneate nucleus, gracile nucleus, nucleus of spinal tract of trigeminal nerve, nucleus medullae oblongatae centralis dorsalis; bilateral (with homolateral predominance) locus ceruleus, nucleus reticularis pontis oralis, laterodorsal tegmental nucleus, substantia nigra, sub-parafascicular nucleus, perifornical nucleus; bilateral medial parabrachial nucleus, deep tegmental nucleus of midbrain, lateral hypothalamic area; homolateral deep layer of superior colliculus, zona incerta; contralateral nucleus of solitary tract; and posteromedian septum, central tegmental nucleus, dorsal nucleus of the raphe. The afferent neurons from cuneate nucleus, gracile nucleus, nucleus of spinal tract of trigeminal nerve, nucleus of solitary tract mainly located below the level of obex. The results mentioned above suggested that the inferior colliculus is not only an auditorial relay nucleus, but also a complex body which is of different functions.
ABSTRACT
In the present study ~3H-Leucine or WGA-HRP was injected into the superior colliculus of one side in the rat.The terminal areas of the efferent projection fibers from the superior colliculus were examined. The efferent fibers of the superfical layer of the superior colliculus descended ipsilaterally to terminate in the parabigeminal nucleus(predominantly the dorsal and ventral part of the same side)and dorso-lateral part of the ipsilateral pontine nucleus.Ascending projections terminated to the medial geniculate nucleus,the posterior pretectal nucleus and latero-posterior nucleus of the thalamus(all bila- terally,but with ipsilateral predominance),the ipsilateral medial and lateral optic nuclei,and the dorsal and ventral lateral geniculate nucleus.In addition,labeled granules were also found in bilateral optic tracts and the optic chiasma. The efferent fibers of the middle and deep layers terminated to the ipsilateral central gray,the nucleus of Darkschewitsch,the interstitial nucleus of Cajal,the cuneiform nucleus and the contralateral superior colliculus.Ascending fibers ter- minated to the medial geniculate nucleus,the suprageniculate nucleus,the anterior- pretectal nucleus,the postero-lateral nucleus of the thalamus(all bilaterally,but more on the ipsilateral side),the parafascicular nucleus,the zona incerta,the ventral nucleus of the thalamus(all ipsilaterally).Descending fibers terminated to ipsilateral parabigeminal area and the parabigeminal nucleus,the dorso-lateral part of the pontine nucleus,the lateral part of the inferior colliculus,the reticular formation of the medulla oblongata and pons,and the lateral part of the inferior olive.The fibers terminated also to contralateral nuclei such as the parabigeminal nucleus,the medial part of the reticular formation of the medulla oblongata and ports,the medial accessory nucleus of the inferior olive,the anterior horn of the cervical spinal cord.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
40 ?m in diameter) were accounted for about 15％, and the rest were medium-and small-sized cells.
ABSTRACT
Neurons descending from the griseum centrale mesencephali, nucleus Darkschewitsch and nucleus interstitialis of Cajal to the nucleus raphe magnus and adjacent reticular formation (nucleus reticularis gigantocellularis and nucleus reticularis pontis caudalis) were identified in 9 adult cats with the retrograde HRP method. In the griseum centrale mesencephali, the labeled neurons were found bilaterally but slightly more ipsilaterally. In the nucleus Darkschewitscb and nucleus interstitialis of Cajal, the labeled neurons were consistently found in its rostral part ipsilateral to the injected side at the level of the posterior commissure. In addition, in 5 of the 9 cases, a few labeled neurons were observed in the nucleus raphe dorsalis.