The nucleus raphe dorsalis of the rat and its projection upon the caudatoputamen. A combined cytoarchitectonic, immunohistochemical and retrograde transport study

The nucleus raphe dorsalis of the albino rat has been studied in the following three ways: (1) the cell mass was subjected to a detailed cytoarchitectonic analysis, based upon Nissl-stained material; (2) serotonin--as well as the noradrenaline--immunoreactive neurons present in the area of the nucleus raphe dorsalis were plotted; (3) following large injections of the fluorescent dye propidium iodide into the caudatoputamen complex, the cells in the nucleus raphe dorsalis projecting to this complex were labeled and subsequently stained with an antibody against serotonin. Cytoarchitectonic analysis showed that three cell types are present within the confines of the nucleus raphe dorsalis: small, medium and large. Moreover, differences in concentrations of cell bodies made it possible to subdivide the nucleus raphe dorsalis into four regions. Immunohistochemical analysis showed that the borders of the serotoninergic cell groups B6 and B7 of DAHLSTROM and FUXE do not coincide with those of the nucleus raphe dorsalis. Serotonin-immunoreactive perikarya in the nucleus raphe dorsalis were categorized as medium and large neurons; noradrenaline-immunoreactive neurons in the nucleus raphe dorsalis do all belong to the category--large neurons. With the combined use of immunofluorescence and fluorescent retrograde tracing, it was found that the projection from the nucleus raphe dorsalis to the caudatoputamen complex originates from serotoninergic as well as non-serotoninergic cells, both of which can be categorized as being medium-sized neurons. The data presented in this paper provides a guide for further studies of afferent and efferent connections of the nucleus raphe dorsalis and for electrophysiological experiments on its constituent neurons.     

大鼠脑内5-HT能神经元对咽肌的支配及调控

用ＰＲＶ和５－ＨＴ免疫组织化学双标记方法研究脑内５－ＨＴ能神经元对咽肌的神经支配及调控。观察到中缝核群的中缝苍白核、中缝隐核、中缝大核、中缝桥核、中缝正中核、中缝背核、和中缝尾侧线形核等部位有ＰＲＶ和５－ＨＴ双标记细胞,直接证明中缝核群的５－ＨＴ能神经元投射到支配咽肌的疑核运动神经元和孤束核中的前运动神经元,调控咽肌的运动。并推测脑干中缝核群中的５－ＨＴ能神经元对咽肌运动的调控可能经由５ＨＴ３和５ＨＴ１Ａ两种受体介导。     

Ontogenesis of serotoninergic nuclei in the rat stem

The development of central serotoninergic neurons has been investigated with immunohistochemical techniques using the indirect peroxidase-antiperoxidase (PAP) method in 16-and 19-day-old rat embryos, in 1, 10 and 26 days old young and in adult animals. Immunoreactive neurons were present on embryonic day 16 in the subventricular area of the brain stem. First the countour of nucleus raphe dorsalis became distinct in the subventricular cell mass of the lower midbrain. In the ventral part of the tegmentum, cells were grouped along the midline in bilateral columns from which the nucleus centralis superior, the nucleus raphe pontis and the nuclei pontis differentiated. These nuclei were well defined in the newborn on either side of the midline, and the nucleus centralis superior and nucleus raphe pontis were fused on the midline in 10-day old rat. In the ventral part of the pons and medulla, a bilateral cell mass was also found along the midline. A number of immunoreactive cells moving off the midline constituted the nucleus raphe magnus which was formed on 19. embryonis day. Another contingent of immunoreactive cells remained at the midline and formed the nuclei raphe obscurus and pallidus. In newborn rat, these nuclei were well separated from the nucleus raphe magnus. They would later fuse on the midline, whereas the nucleus raphe magnus would remain a bilateral structure.     

大鼠延髓网状背侧亚核内5-羟色胺能、P物质样和脑啡肽样阳性终末的中枢起源

研究用荧光金（ＦＧ）逆行追踪与免疫荧光组化染色相结合的双标技术对大鼠脑干向延髓网状背侧亚核（ＳＲＤ）的５┐羟色胺（５┐ＨＴ）能、Ｐ物质（ＳＰ）能和亮氨酸┐脑啡肽（Ｌ┐ＥＮＫ）能投射进行了观察。将ＦＧ注入ＳＲＤ后,ＦＧ逆标神经元主要见于中脑导水管周围灰质、脑干中缝核簇（中缝背核、中缝正中核、中缝桥核、中缝大核、中缝隐核和中缝苍白核）、巨细胞网状核α部、延髓网状结构的内侧部和外侧部、延髓外侧网状核、三叉神经脊束核尾侧亚核和孤束核。５┐羟色胺（５┐ＨＴ）样、Ｐ物质（ＳＰ）样和亮氨酸脑啡肽（Ｌ┐ＥＮＫ）样阳性神经元主要见于中脑导水管周围灰质、脑干中缝核簇和巨细胞网状核α部;此外,ＳＰ样和Ｌ┐ＥＮＫ样阳性神经元还见于臂旁核、背外侧被盖核和孤束核。ＦＧ逆标并呈５┐ＨＴ样、ＳＰ样或Ｌ┐ＥＮＫ样阳性的双标神经元也主要见于中脑导水管周围灰质、脑干中缝核簇和巨细胞网状核α部,尤其是位于延髓中缝核团内的双标神经元数量较多。本研究的结果说明ＳＲＤ内的５┐ＨＴ样、ＳＰ样和Ｌ┐ＥＮＫ样阳性终末主要来自中脑导水管周围灰质、脑干中缝核簇和巨细胞网状核α部,向ＳＲＤ发出５┐ＨＴ能、ＳＰ能和Ｌ┐ＥＮＫ能投射的上述核团对ＳＲＤ发挥“弥漫性伤害抑     

Chemically defined collateral projections from the pons to the central nucleus of the amygdala and hypothalamic paraventricular nucleus in the rat

Triple fluorescence labelling was employed to reveal the distribution of chemically identified neurons within the pontine laterodorsal tegmental nucleus and dorsal raphe nucleus which supply branching collateral input to the central nucleus of the amygdala and hypothalamic paraventricular nucleus. The chemical identity of neurons in the laterodorsal tegmental nucleus was revealed by immunocytochemical detection of choline-acetyltransferase or substance P; in the dorsal raphe nucleus, the chemical content of the neurons was revealed with antibody recognizing serotonin. The projections were defined by injections of two retrograde tracers, rhodamine-and fluorescein-labelled latex microspheres, in the central nucleus of the amygdala and paraventricular nucleus, respectively. Neurons projecting to both the central nucleus of the amygdala and the paraventricular nucleus were distributed primarily within the caudal extensions of the laterodorsal tegmental nucleus and dorsal raphe nucleus. Approximately 11% and 7% of the labelled cells in the laterodorsal tegmental nucleus and dorsal raphe nucleus projected via branching collaterals to the paraventricular nucleus and central nucleus of the amygdala. About half of these neurons in the laterodorsal tegmental nucleus were cholinergic, and one-third were substance-P-ergic; in the dorsal raphe nucleus, approximately half of the neurons containing both retrograde tracers were serotonergic. These results indicate that pontine neurons may simultaneously transmit signals to the central nucleus of the amygdala and paraventricular nucleus and that several different neuroactive substances are found in the neurons participating in these pathways. This coordinated signalling may lead to synchronized responses of the central nucleus of the amygdala and paraventricular nucleus for the maintenance of homeostasis. Interactions between different neuroactive substances at the target site may serve to modulate the responses of individual neurons.     

Substance P-immunoreactive neurons in the brainstem of the cat related to cardiovascular centers

Summary The distribution of substance P-immunoreactivity (SP-IR) in the brainstem and spinal cord of normal and colchicine-pretreated cats was analysed using the peroxidase-antiperoxidase (PAP) technique. Numerous SP-IR fibers are present in the nucleus solitarius, nucleus dorsalis nervi vagi and nucleus spinalis nervi trigemini, various parts of the formatio reticularis, substantia grisea centralis mesencephali, locus coeruleus and nucleus parabrachialis. SP-IR perikarya occur in the substantiae gelatinosa and intermedia of the spinal cord, the nucleus spinalis nervi trigemini-pars caudalis, the nucleus dorsalis nervi vagi, and the nucleus solitarius, as well as in the adjacent formatio reticularis and the medullary nuclei of the raphe. In addition, SP-IR cell bodies are located in the nuclei raphe magnus and incertus, ventral and dorsal to the nucleus tegmentalis dorsalis (Gudden), nucleus raphe dorsalis, substantia grisea centralis mensencephali, locus coeruleus, nucleus parabrachialis and colliculus superior.The results indicate that SP-IR neurons may be involved in the regulation of cardiovascular functions both at the central and peripheral level. A peripheral afferent portion seems to terminate in the nucleus solitarius and an efferent part is postulated to originate from the nucleus dorsalis nervi vagi and from the area of the nuclei retroambiguus, ambiguus and retrofacialis.     

5—HT能纤维向猫脊髓膈神经核及延髓膈肌前运动神经元的投射

实验在6只成年猫上进行,将WGA－HRP微量注入C5膈神经核内,通过逆行追踪及5－HT免疫组织化学FITC荧光双重标记方法,研究了中缝核5－HT能神经元向脊髓膈神经核的投射,同时观察了延髓膈肌产运动神经元接受5－HT能纤维投射的情况,结果在中缝苍白核观察到较多的HRP－5－HT双标记神经元,在中缝大核,中缝隐核观察到少数散在的双标记神经元,在延髓疑核,孤束核腹外侧区域的HRP单核记神经元（即膈肌前运动神经元）周围观察到5－HT能轴突末梢,结构表明：发自中缝苍白核5－HT能神经元的传出纤维可投射到脊髓膈神经核,延髓膈肌前运动神经元接受5－HT能纤维的传入投射。     

Effect of specific serotonergic lesions on cholinergic neurons in the hippocampus,cortex and striatum

Local injection of 5, 7-dihydroxytryptamine into the median raphe nucleus of rats pretreated with desipramine decreases the serotonin content of the hippocampus and cortex. The turnover of acetylcholine, as measured by the rate of decline of acetylcholine content after hemicholinium-3, the rate of decline of acetylcholine content after hemicholinium-3, is not affected in the hippocampus or the striatum, but is increased in the cortex by such treatment. Local injection of 5, 7-dihydroxytryptamine into the dorsal raphe nucleus of desipramine-treated rats decreases the serotonin content of the hippocampus, cortex, and striatum. The turnover of acetylcholine is increased in the hippocampus and cortex, but not affected in the striatum. Thus, serotonergic neurons from the median raphe nucleus appear to tonically inhibit cholinergic neurons in the cortex, and serotonergic neurons from the dorsal raphe nucleus appear to tonically inhibit cholinergic neurons in the hippocampus and cortex. These serotonergic neurons do not appear to act tonically on striatal cholinergic neurons.     

Influence of the medial raphe nucleus damage on discharge activity of the central and bazolateral nuclei of the amygdala

It has been revealed pronounced differences between neuronal discharge activity of central and basolateral nuclei of amygdala. After midbrain raphe medial nucleus damage discharge activity of amygdalar nuclei markedly changes, mainly by reciprocal manner. It is suggest that serotonergic afferentations from nucleus raphe to show various influence upon discharge activity of central and lateral nuclei of amygdala.     

Independent effects of cholinergic and serotonergic lesions on acetylcholine and serotonin release in the neocortex of the rat

Rats received a unilateral lesion of the nucleus basalis magnocellularis (NBM) by infusion of ibotenic acid. In addition, the dorsal raphe nucleus was lesioned by infusion of 5,7-dihydroxytryptamine (5,7-DHT). The release of acetylcholine (ACh), choline, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) was measured in the frontal neocortex by means of microdialysis. Lesions of the NBM, but not the raphe nucleus, reduced the release of ACh significantly (–47%). The release of 5-HT and 5-HIAA was reduced by raphe lesions (–44% and –79%), but not by NBM lesions. In no case did the combined lesion affect neurotransmitter release more than a single lesion. These results suggest that serotonergic projections from the dorsal raphe nucleus are not involved in tonic inhibition of ACh release in the neocortex.     

大鼠中缝核群中生长抑素样神经元对咽肌前运动神经元的支配-PRV和SOM免疫荧光双标记法研究

用PRV和SOM免疫荧光双标记法研究了大鼠中缝核群中SOM样神经元对咽肌前运动神经元的调控。PRV注射大鼠咽肌后,在中缝苍白核、中缝隐核、中缝大核和中缝背核中可见少量PRV和SOM双标记细胞。首次证明了大鼠中缝核群中SOM样神经元对咽肌前运动神经元的支配。推测中缝核群中的SOM可能和咽肌运动的精确调控有关。     

电刺激大鼠尾核头部镇痛的中枢效应—[^3H]—2脱氧...

Sokoloff's 2-deoxyglucose (2-DG) autoradiographic technique was used to identify changes of glucose metabolic rate in the rat brain following unilateral stimulation of the head of the caudate nucleus. The results were as follows. The local glucose metabolic rate after noxious stimulation was increased in the somatosensory cortex, cingulate cortex, ventroposterior and parafascicular nucleus of the thalamus, septal area, habenular nucleus, head of caudate nucleus, periaqueductal gray (PAG) and dorsal raphe nucleus (P < 0.05). After stimulating the head of the caudate nucleus, the local glucose metabolic rate of nucleus raphe magnus (rm) and nucleus paragigantocellularis (pgcl) was increased significantly and that of the PAG and dorsal raphe nucleus had a tendency to increase, while stimulation of the head of caudate nucleus could partially abolish the increased glucose metabolic rate in the somatosensory cortex, cingulate cortex, ventroposterior and parafascicular nucleus of the thalamus, septal area and habenular nucleus as induced by noxious stimulation. These results suggest that caudate stimulation is able to depress the activation of some brain structures related to nociception and to activate those related to antinociception. The pgcl, rm, PAG and dorsal raphe nucleus might be the key structures participating in the caudate stimulation produced analgesia.     

Firing of 5-HT neurones in the dorsal and median raphe nucleus in vitro shows differential alpha1-adrenoceptor and 5-HT1A receptor modulation

The median raphe nucleus and dorsal raphe nucleus together are the major source of ascending 5-HT projections. Here, using in vitro extracellular single unit electrophysiology we examined the responses of individual neurones in the rat median raphe nucleus and dorsal raphe nucleus to alpha(1)-adrenoceptor and 5-HT(1A) receptor activation and made comparisons between the two nuclei. In the presence of the alpha(1)-adrenoceptor agonist phenylephrine (1microM) all spontaneously active neurones recorded in the median and dorsal raphe nuclei fired slowly (<5Hz) and regularly. Most were inhibited by 5-HT (10-50microM), although a few were excited by 5-HT. 5-HT-induced inhibition was attenuated by the 5-HT(1A) receptor antagonist, WAY100635 (100nM). Compared to those in the dorsal raphe nucleus, the neurones in the median raphe nucleus which were inhibited by 5-HT had: (1) lower basal firing rates in the continuous presence of phenylephrine (1microM), (2) smaller excitatory responses to higher concentrations of phenylephrine (3-10microM), (3) smaller excitatory responses to brief application of norepinephrine (10-100microM) and (4) smaller inhibitory responses to 5-HT (10-50microM). The lower sensitivity of median raphe neurones to alpha(1)-adrenoceptor excitation and 5-HT(1A) receptor inhibition will have consequences for 5-HT neurotransmission in forebrain regions innervated by the two nuclei.     

Influence of cold and warm acclimation on neuronal responses in the lower brain stem

Neurons in two lower brain stem areas, the nucleus raphe magnus and the subcoeruleus region, have been shown to be part of the thermoafferent system. It is concluded from microcut experiments in unanaesthetized guinea pigs that inhibition of shivering caused by nucleus raphe magnus stimulation is mediated partly by ascending and partly by descending efferents of the nucleus raphe magnus. Electrical stimulation of the subcoeruleus area caused excitatory metabolic responses. Interruption of the ascending efferents of the subcoeruleus area did not prevent the metabolic activation. It is concluded that the excitatory responses are partly mediated by descending efferents of the subcoeruleus area. The descending pathways project mainly to motoneurone pools and to dorsal horn cells. In cold-acclimated guinea pigs, the average maximum activity of bell-shaped subcoeruleus cold-responsive units was reduced significantly in comparison with cold-responsive neurons in animals acclimated to normal room temperature. Furthermore, peak activity of warm-responsive units in the nucleus raphe magnus was larger in cold-acclimated animals than in animals acclimated to normal room temperature. These neuronal changes may contribute via descending lower loops and via ascending upper loops to long-term slope reduction of metabolic cold defence and shivering threshold displacements.     

Comparative distribution of nitric oxide synthase- and serotonin-containing neurons in the raphe nuclei of four mammalian species

 Monoclonal antibodies were generated against serotonin (5-HT) and the C-terminal portion of the neuronal form of nitric oxide synthase (nNOS), the enzyme producing nitric oxide in neurons. These antibodies were used to compare the distribution of 5-HT- and nNOS-containing neurons in the raphe nuclei of four animal species (rat, mouse, guinea pig, and cat). It was found that the rat was the only species in which the raphe nuclei contain a substantial number of nNOS-immunoreactive (IR) cell bodies. In this species and as observed by other authors, all mesencephalic raphe nuclei contained nNOS-IR cells, the largest group being located in the nucleus raphe dorsalis. The coexistence of nNOS and 5-HT immunoreactivities in these nuclei was visualized by double labeling. In the medulla, the nuclei raphe magnus and obscurus displayed a rather low number of nNOS-IR neurons. In the other species, nNOS-IR cell bodies were found in very low numbers, whatever raphe nucleus was considered. The rostral pole of the nucleus raphe dorsalis and the nuclei raphe magnus and obscurus contained a few nNOS-IR neurons which did not show any coincidence with the 5-HT neurons. In addition, nNOS-IR axons were rare. It is concluded that in the mouse, guinea pig, and cat the involvement of nitric oxide in functions subserved by 5-HT within the raphe nuclei might be minimal. Accepted: 5 May 1998     

Stress-related serotonergic systems: implications for symptomatology of anxiety and affective disorders

Previous studies have suggested that serotonergic neurons in the midbrain raphe complex have a functional topographic organization. Recent studies suggest that stimulation of a bed nucleus of the stria terminalis-dorsal raphe nucleus pathway by stress- and anxiety-related stimuli modulates a subpopulation of serotonergic neurons in the dorsal part of the dorsal raphe nucleus (DRD) and caudal part of the dorsal raphe nucleus (DRC) that participates in facilitation of anxiety-like responses. In contrast, recent studies suggest that activation of a spinoparabrachial pathway by peripheral thermal or immune stimuli excites subpopulations of serotonergic neurons in the ventrolateral part of the dorsal raphe nucleus/ventrolateral periaqueducal gray (DRVL/VLPAG) region and interfascicular part of the dorsal raphe nucleus (DRI). Studies support a role for serotonergic neurons in the DRVL/VLPAG in inhibition of panic-like responses, and serotonergic neurons in the DRI in antidepressant-like effects. Thus, data suggest that while some subpopulations of serotonergic neurons in the dorsal raphe nucleus play a role in facilitation of anxiety-like responses, others play a role in inhibition of anxiety- or panic-like responses, while others play a role in antidepressant-like effects. Understanding the anatomical and functional properties of these distinct serotonergic systems may lead to novel therapeutic strategies for the prevention and/or treatment of affective and anxiety disorders. In this review, we describe the anatomical and functional properties of subpopulations of serotonergic neurons in the dorsal raphe nucleus, with a focus on those implicated in symptoms of anxiety and affective disorders, the DRD/DRC, DRVL/VLPAG, and DRI.     

Serotonin-mediated cardiovascular responses to electrical stimulation of the raphe nuclei in the rat.

The dorsal and median raphe nuclei in rats were electrically stimulated and blood pressure and heart rate were recorded. Stimulation of each raphe nucleus caused an increase in blood pressure without affecting heart rate. The size of the increase in blood pressure depended upon the stimulus-intensity.Significant increases were already obtained with 5 sec. trains of 0.3 msec., 200 μA stimuli given at a frequency of 50 Hz. The increases in blood pressure could be obtained with electrodes within the raphe nuclei.Pretreating rats with para-chlorophenylalanine (pCPA, 100 mg/kg.day for 3 days) significantly diminished the increases in blood pressure obtained during electrical stimulation of the median raphe nucleus. However, similar pretreatment did not affect blood pressure rises induced by dorsal raphe stimulation.These data are discussed in relation to the role of central serotoninergic mechanisms in cardiovascular control.     

Evidence for projections from medullary nuclei onto serotonergic and dopaminergic neurons in the midbrain dorsal raphe nucleus of the rat

Summary The anterograde tracer Phaseolus vulgaris-leucoagglutinin was injected into the medial nucleus of the solitary tract and into the rostral dorsomedial medulla. A sequential two-color immunoperoxidase staining was accomplished in order to demonstrate the co-distribution of presumed terminal axons with chemically distinct neurons in the dorsal raphe nucleus of the midbrain central gray, i.e., B7 serotonergic and A10dc dopaminergic neurons. Black-stained efferent fibers from the medial nucleus of the solitary tract and the rostral dorsomedial medulla intermingled with brown-stained serotonergic (5-hydroxytryptamine-immunoreactive) or dopaminergic (tyrosine hydroxylase-immunoreactive) neurons. Light microscopy revealed that the black-stained efferent axons exhibited numerous en passant and terminal varicosities that were often found in close apposition to brown-stained serotonergic and dopaminergic somata, and to proximal and distal dendrites and dendritic processes. The close association of immunoreactive elements suggests the presence of axo-somatic and axodendritic synaptic contacts of medullary fibers with serotonergic and dopaminergic neurons in the dorsal raphe nucleus. These projections could be involved in the modulation of dorsal raphe neurons, depending on the autonomic status of an animal.     

Preliminary observations on the distribution of serotoninergic and cerebellar-projecting neurons of the raphe nuclei of the brain stem

Cerebellar projection from raphe nuclei were investigated in rabbit by using retrograde transport of HRP and serotonergic mapping by direct fluorescence. A close topographical correlation between the HRP labeled cells and the serotonergic neurons has been observed. The current study has demonstrated the presence of paramedian and lateral cells whose cytoarchitecture is identical with midline cells of many raphe nuclei. All of the raphe nuclei except the linear nuclei, contained serotonergic perikarya. The midline and paramedian portions of the nuclei raphe obscurus, pallidus, magnus, and nucleus raphe dorsalis contained principally serotonergic neurons; the lateral portions of the medullary raphe nuclei and the nuclei raphe pontis and centralis superior contained a significant number of non-fluorescent cells. In these regions, fluorescent sections often revealed the size, shape, and orientation of the perikarya and dendrites; further verification of cytoarchitectural characteristics of these neurons depended heavily upon these clues.     

5-羟色胺和一氧化氮合酶在大鼠中脑导水管周围灰质 和中缝核簇神经元内的共存

实验采用 NADPH组织化学和 5 - HT免疫组织化学双重显色方法研究了 5 - HT和一氧化氮合酶在大鼠中脑导水管周围灰质 (PAG)和中缝核簇神经元的分布特征及共存情况。结果表明 ;(1 )在 PAG腹外侧区中观察到大量的 NOS阳性神经元和 5 - HT样免疫阳性神经元 ,但是 NOS/ 5 - HT双标神经元较少 ,仅占该区 5 - HT样免疫阳性神经元 2 0 .1 % ,并且主要分布在该区的内侧部 ;在 PAG的背外侧区中观察到密集的 NOS阳性神经元 ,但是几乎未见 5 - HT免疫阳性神经元分布。(2 )在中缝核簇的大多数亚核内均可观察到大量的 NOS神经元和 5 - HT免疫阳性神经元。在中缝背核的内侧部、中缝背核的尾侧部、中缝正中核、尾侧线形核、中缝大核和中缝隐核内双标神经元分别占所在部位中 5 - HT免疫阳性神经元的 44 .6 %、5 3.4%、 44 .4%、 2 6 .2 %、 2 6 .7%和 2 1 .8%。然而在中缝苍白核内仅偶见少数双标神经元。研究结果表明 ,在 PAG和中缝核簇的一些神经元内 5 - HT可以与 NOS共存 ,提示这两种神经活性物质在功能上可能存在着某种相关性 ,有关这些双标神经元的功能意义尚需进一步研究。