Analgesia caused by an excitation generator formed in the mesencephalon

In experiments on albino rats an excitation generator was formed with tetanus toxin in the dorsal nucleus of the midbrain raphe. The formation of an excitation generator in this nucleus was shown to produce general analgesia manifested against physiological (nociceptive stimulation) and central pathological pain (a pain syndrome of spinal origin). It is concluded that prolonged analgesia arising during activation of certain brain structures is due to the appearance of excitation generators in them, which cause prolonged activation of those structures.Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 2, pp. 145–148, February, 1977.     

高频电刺激大鼠丘脑底核抑制背侧中缝核5-羟色胺表达

本研究探讨高频电刺激丘脑底核对大鼠背侧中缝核5-羟色胺(5-HT)表达的影响。实验动物分两组,刺激组给予高频电流(130Hz,100μA,60μs)刺激大鼠右侧丘脑底核,对照组大鼠右侧丘脑底核植入电极,但无电流输出。刺激结束后,用免疫组织化学方法染色背侧中缝核5-HT能神经元,检测背侧中缝核5-HT能神经元的数量和平均灰度值。结果显示电刺激组背侧中缝核5-HT阳性神经元数目与对照组比明显减少(t(13)=3.786,P=0.002),并且神经递质5-HT表达量减少,平均灰度值显著增高(t(13)=7.917,P<0.001)。本实验结果表明高频电刺激丘脑底核对背侧中缝核5-HT能神经元有抑制作用,在应用高频电刺激丘脑底核治疗Parkison病运动障碍时出现的情绪障碍可能与其有关。     

An experimental vestibulopathy produced by formation of a pathologically enhanced excitation generator in the vestibular nucleus (the determinant dispatch station phenomenon)

The possibility of formation of a pathologically enhanced excitation generator in the vestibular nucleus of the medulla through a disturbance of inhibition in that nucleus was demonstrated and, as a result, the animals developed rotatory movements toward the opposite side. Experimental electrical stimulation or coagulation of the lateral vestibular nucleus showed that the pathologically enhanced excitation generator is based on a system of vestibular neurons which organizes a synchronous volley along the vestibulo-spinal tracts. It is concluded that the pathologically enhanced excitation generator formed in the lateral vestibular nucleus as a result of disturbance of inhibition lies at the basis of the hyperactive determinant dispatch station responsible for the syndrome of vestibulopathy.Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 2, pp. 147–150, February, 1976.     

大鼠中缝背核一氧化氮合酶神经元投射纤维在大脑皮质微血管的分布

目的：研究通过损毁脑干中缝背核(DR)，探讨中缝背核NOS阳性神经元是否投射分布于大脑皮质微血管。方法：将16只SD雄性成年大鼠分为实验组与对照组。对实验组大鼠中缝背核微量注射喹啉酸，饲养1w，灌注固定，然后将大脑及脑干作冠状冰冻切片，NADPH—d组化染色。结果：实验组大鼠的中缝背核被有效损毁，其NOS阳性神经元的数量减少了59．1％(P＜0．001)。额、顶叶皮质NOS阳性纤维终末减少了32．1％(P＜0．05)，其中附着于皮质微血管的NOS阳性纤维终未了减少了37．8％(P＜0．01)。而枕额叶皮质NOS阳性纤维终末也减少了32．8％(P＜0．05)，其中附着于皮质微血管的阳性纤维终末减少了39．4％(P＜0．01)。结论：位于中缝背核的NOS阳性神经元投射分布于大脑皮质微血管，可能参与大脑皮质血流量的调节。     

双轴旋转运动刺激后大鼠中缝大核神经元活动分析

目的:分析大鼠经引发晕动病的双轴旋转运动刺激后,中缝背核(DR)内5-HT能神经元激活状况,以探讨5-HT水平与前庭刺激的关系.方法:将雄性SD大鼠随机分成两组:对照组和双轴旋转运动刺激组.所有动物装入定做的有机玻璃圆筒内,并于黑暗中进行如下处理2h:运动刺激组动物以电动马达驱动的双轴旋转运动刺激;对照组动物放置在距刺激仪器20 cm的位置.应用包含DR的冠状脑切片,以双重免疫荧光标记技术标记5-HT和Fos蛋白,并对标记神经元进行计数和统计分析.结果:对照组和旋转运动刺激组的Fos阳性神经元、5-HT阳性神经元以及Fos/5-HT双标记神经元的数目分别是:93.4 ±12.0 vs 153.1 ±21.1、528.5±36.0vs 531.1±23.4和15.1 ±11.3 vs 30.8 ±11.3.t检验分析显示两组Fos阳性神经元数目有显著性差异(P＜0.05);Fos/5-HT双标神经元数目在旋转运动刺激后有增加趋势.结论:引发晕动病的双轴旋转运动能激活中缝背核内的神经元,其中的5-HT能神经元也对刺激有反应.     

Anterograde tracing of projections from the dorsal raphe nucleus to the vestibular nuclei

This study used the anterograde transport of biotinylated dextran amine (BDA) to identify the course and terminal distribution of projections from the dorsal raphe nucleus (DRN) to the vestibular nuclei in rats. After iontophoretic injection of BDA into the medial and lateral regions of DRN, anterogradely labeled fibers descend within the medial longitudinal fasciculus and the ventricular fiber plexus to terminate within two discrete regions of the vestibular nuclear complex. One terminal field was located primarily ipsilateral to the injection site and involved rostrodorsal aspects of the vestibular nuclei, including superior vestibular nucleus and rostral portions of the medial vestibular nucleus (MVN) and lateral vestibular nucleus (LVN). The other terminal field involved caudoventral aspects of both ipsilateral and contralateral MVN and LVN and was less heavily innervated. These findings confirm that the vestibular nuclei are targeted by a regionally-selective projection from the DRN. The segregation of DRN terminals into anatomically distinct fields indicates that the DRN-vestibular nucleus projections are organized to selectively modulate processing within specific functional domains of the vestibular nuclear complex. In particular, these terminal fields may be organized to modulate vestibular regions involved in eye movement-related velocity storage, coordination of vestibular and affective responses, and the bilateral coordination of horizontal eye movement reflexes.     

Prolongation of sleep as the result of the creation of a generator of pathologically enhanced excitation in the orbital cortex

In acute experiments on cats injection of tetanus toxin, which disturbs various types of inhibition, into the orbital cortex caused the formation of a local generator of pathologically enhanced excitation in that region. In chronic experiments on cats with such a generator in the orbital cortex pathological changes of sleep appeared: a decrease in the duration of wakefulness and the development of a prolonged sleep state, while the normal ratio between slow-wave and paradoxical stages in the sleep continuum was preserved. The results confirm the view that the orbitofrontal cortex participates in the induction of sleep and they develop the general concept of the role of determinant structures in the activity of the nervous system and the theory of generator mechanisms of neuropathological syndromes characterized by hyperactivity of its systems.Laboratory of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Department of Pathological Physiology, N. I. Pirogov Odessa Medical Institute. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 11, pp. 531–534, November, 1977.     

Serotonergic and nonserotonergic neurons in the dorsal raphe nucleus send collateralized projections to both the vestibular nuclei and the central amygdaloid nucleus

Using a combination of double retrograde tracing and serotonin immunofluorescence staining, we examined whether individual serotonergic and nonserotonergic neurons in the dorsal raphe nucleus are sources of collateralized axonal projections to vestibular nuclei and the central amygdaloid nucleus in the rat. Following unilateral injections of Diamidino Yellow into the vestibular nuclei and Fast Blue into the central amygdaloid nucleus, it was observed that approximately one-fourth of the dorsal raphe nucleus neurons projecting to the vestibular nuclei send axon collaterals to the central amygdaloid nucleus. Immunofluorescence staining for serotonin revealed that more than half of the dorsal raphe nucleus neurons from which these collateralized projections arise contain serotonin-like immunoreactivity. These findings indicate that a subpopulation of serotonergic and nonserotonergic dorsal raphe nucleus cells may act to co-modulate processing in the vestibular nuclei and the central amygdaloid nucleus, regions implicated in the generation of emotional and affective responses to real and perceived motion.     

Cellular profile of the dorsal raphe lateral wing sub-region: Relationship to the lateral dorsal tegmental nucleus

As one of the main serotonergic (5HT) projections to the forebrain, the dorsal raphe nucleus (DRN) has been implicated in disorders of anxiety and depression. Although the nucleus contains the densest population of 5HT neurons in the brain, at least 50% of cells within this structure are non-serotonergic, including a large population of nitric oxide synthase (NOS) containing neurons. The DRN has a unique topographical efferent organization and can also be divided into sub-regions based on rostro-caudal and medio-lateral dimensions. NOS is co-localized with 5HT in the midline DRN but NOS-positive cells in the lateral wing (LW) of the nucleus do not express 5HT. Interestingly, the NOS LW neuronal population is immediately rostral to and in line with the cholinergic lateral dorsal tegmental nucleus (LDT). We used immunohistochemical methods to investigate the potential serotonergic regulation of NOS LW neurons and also the association of this cell grouping to the LDT. Our results indicate that >75% of NOS LW neurons express the inhibitory 5HT_1A receptor and are cholinergic (>90%). The findings suggest this assembly of cells is a rostral extension of the LDT, one that it is subject to regulation by 5HT release. As such the present study suggests a link between 5HT signaling, activation of cholinergic/NOS neurons, and the stress response including the pathophysiology underlying anxiety and depression.     

Expression of galanin and nitric oxide synthase in subpopulations of serotonin neurons of the rat dorsal raphe nucleus

The dorsal raphe nucleus (DR) of the rat was studied with triple labeling immunofluorescence histochemistry to evaluate the quantitative relationships between neurons expressing 5-hydroxytryptamine (5-HT), the neuropeptide galanin (GAL) and the nitric oxide (NO) synthesizing enzyme NO synthase (NOS). In addition retrograde tracing studies were performed. It could be established that a high percentage (between 40 and 60%) of the 5-HT neuron profiles in the ventromedial and dorsomedial subgroups of the DR contained both GAL and NOS after colchicine treatment. This triple coexistence was lower in the dorso-lateral subgroup and much lower in the lateral subgroup (down to 5%). All GAL neuron profiles contained 5-HT, and they constituted up to 80% of all labeled profiles in the rostral ventromedial and caudal dorsomedial subgroups, with the lowest percentage in the lateral subgroup (45%). The percentage of 5-HT-alone neuron profiles in these four subgroups varied between 15–40%. The proportion of 5-HT/NOS neurons was low (a few percent) at all levels, and this was the case also for NOS-alone neuron profiles except in the lateral subgroup, where 10–20% were of this type. It could be established that some 5-HT/GAL/NOS neurons project to the striatum. These retrogradely labeled cells were mainly found in the mid-line subgroups. In the striatum a moderately dense 5-HT fiber network and numerous NOS-positive cell bodies and fibers could be observed. However, only a few, weakly fluorescent GAL fibers were found and in a small number of cases it could be shown or was likely that 5-HT and GAL coexisted. No evidence for coexistence between 5-HT and NOS was obtained. The present findings strongly suggest that a large proportion of the DR 5-HT neurons can synthesize and release two additional messenger molecules, GAL and NO. Furthermore, even if the 5-HT/GAL/NOS neurons project to the striatum, the amounts of GAL and NOS transported to the terminal ramifications in this area are very low. This is in agreement with a very low GAL synthesis in the DR under normal circumstances, which is also indicated by the fact that colchicine treatment is needed to visualize GAL-like immunoreactivity in DR cell bodies. It is possible that NO, and perhaps GAL, in 5-HT neurons exert their main actions at the somatic and dendritic level in the DR.     

大鼠中缝大核向脊髓投射神经元与神经降压素能终末的突触联系

神经降压素(NT)是中枢下行抑制系统的重要神经活性物质。本研究运用免疫组织化学与逆行追踪法相结合的双标技术,在电镜下观察NT能终末与中缝大核(NRM)向脊髓投射神经元的突触联系。在光镜下可见NT阳性纤维和终末散在分布于NRM,但未见NT阳性神经元;将HRP注入腰髓背角后,在NRM内可见比较密集的HRP逆标神经元。在电镜下可见NT阳性终末与HRP逆标神经元的胞体和树突形成以非对称性为主的轴-体突触和轴-树突触。上述结果说明NT可能调控NRM向脊髓背角投射神经元的活动,借此对伤害性信息向中枢的传递发挥抑制效应。     

PTSD样行为异常大鼠中缝背核5-HT1A受体的改变

目的观察创伤后应激障碍(PTSD)样行为异常大鼠中缝背核(DRN)神经元5-HT1A受体表达变化,为探讨PTSD的发病机制提供资料。方法成年健康雄性Wistar大鼠60只,随机分为连续单一刺激(SPS)模型1d、4d、7d组及正常对照组,采用免疫组化、Western blot方法检测PTSD样行为异常大鼠中缝背核神经元5-HT1A受体表达变化。结果 SPS刺激后1d大鼠中缝背核神经元5-HT1A受体表达水平开始逐渐升高,第4天高于第1天,第7天高于第4天。结论 PTSD样大鼠中缝背核神经元5-HT1A受体呈规律性过表达。     

Differential effect of orexins (hypocretins) on serotonin release in the dorsal and median raphe nuclei of freely behaving rats

Orexin (hypocretin)-containing neurons in the perifornical hypothalamus project to widespread regions of the brain, including the dorsal and median raphe nuclei [Peyron C, Tighe DK, van den Pol AN, de Lecea L, Heller HC, Sutcliffe JG, Kilduff TS (1998) Neurons containing hypocretin (orexin) project to multiple neuronal systems. J Neurosci 18:9996-10015; Wang QP, Koyama Y, Guan JL, Takahashi K, Kayama Y, Shioda S (2005) The orexinergic synaptic innervation of serotonin- and orexin 1-receptor-containing neurons in the dorsal raphe nucleus. Regul Pept 126:35-42]. Orexin-A or orexin-B was infused by reverse microdialysis into the dorsal raphe nucleus or median raphe nucleus of freely behaving rats, and extracellular serotonin was simultaneously collected by microdialysis and analyzed by high-performance liquid chromatography. We have found that orexin-A produced a dose-dependent increase of serotonin in the dorsal raphe nucleus, but not in the median raphe nucleus. However, orexin-B elicited a small but significant effect in both the dorsal raphe nucleus and median raphe nucleus. Orexins may have regionally selective effects on serotonin release in the CNS, implying a unique interaction between orexins and serotonin in the regulation of activities including sleep-wakefulness.     

Immunocytochemical and electron microscopic study of serotonin neuronal organization in the dorsal raphe nucleus of the monkey

Serotonin neurons in the dorsal raphe nucleus were identified using an antibody to a serotonin-bovine serum albumin conjugate and the peroxidase anti-peroxidase method. Nerve cell bodies showing serotonin-like immunoreactivity ranged in size from 15 to 22 micron in diameter; their dendrites were also immunoreactive. Immunostaining was present in the cytoplasmic matrix, outer membranes of mitochondria, rough endoplasmic reticulum, multivesicular bodies and dense-cored vesicles. Heavily immunoreactive axonal varicosities contained small round vesicles (18-35 nm) and larger dense-cored vesicles (50-90 nm). Both unmyelinated (0.2-0.5 micron) and myelinated (0.8-1.1 micron) serotonin-like immunoreactive axons were found, often interspersed within bundles of similar caliber unlabeled axons. Serotonin-like immunoreactive somata and dendrites were postsynaptic to numerous unlabeled terminals that contained either (a) clear round vesicles (18-25 nm) with many small dense-cored vesicles (30-50 nm), (b) clear round vesicles (18-25 nm) with large dense-cored vesicles (90-110 nm) or (c) clear round vesicles (18-25 nm) with or without flat vesicles. In addition pairs of unlabeled terminals formed crest synapses onto serotonin-like immunoreactive dendritic spines. This variety of unlabeled terminals making contact with serotonin-like immunoreactive elements suggests that several neuronal systems with possibly different transmitters may regulate serotonin raphe neurons. We occasionally observed serotonin-like immunoreactive dendrites and terminals in apposition to other serotonin-like immunoreactive dendrites with membrane specializations at the site of contact. This might represent a possible site for the self inhibition of serotoninergic neurons reported in physiological studies of the serotonin system in the dorsal raphe nucleus.     

Enhancement of dorsal raphe discharge by medial pontine reticular formation stimulation depends on behavioral state

Single cell activity was recorded with microwire electrodes from the dorsal raphe nucleus (DRN) of cats across multiple cycles of sleep and wakefulness. Electrical stimulation of the medial pontine reticular formation (mPRF) produced a 10-fold enhancement of DRN discharge during wakefulness and slow wave sleep but not during desynchronized sleep. The neuronal mechanisms likely to mediate the state-dependent effects of mPRF stimulation are discussed with regard to the hypothesis that DRN plays a major role in behavioral state control.     

Correlation of evoked potentials in the caudate nucleus and conditioned motor responses

The relevant participation of the caudate nucleus (CN) in motor conditioned responses has been described in different papers. This function could be reflected by changes in its electrical activity. In cats with implanted electrodes in the CN the evoked potentials produced by the conditioned stimulus (light or sound) appeared and increased during the performance of an approaching conditioned response (CR). Extinction of the CR caused decrease in amplitude, while reconditioning had the opposite effect. The potentials did not decrease as long as the conditioning sessions were repeated. The correct performance of the CR was positively correlated at the level of p<0.001 with the amplitude or the appearance of the evoked potentials. The increment of the evoked potentials seems to be independent of the cat's movements since the movements were much more frequent and vigorous during the first training sessions and besides that the increment of the potentials preceded the performance of the CR and persisted during the inhibitory conditioning. The recorded potentials seem to manifest the afferent changes capable of evoking responses in areas not directly connected with the sensory parthways and/or the integration of the information in the CN which subserved the performance of the learned response.     

Projections from the ventral tegmental area and mesencephalic raphe to the dorsal raphe nucleus in the rat

Summary The origins of the dopaminergic innervation of the rat dorsal raphe nucleus (NRD) have been investigated using a combination of fluorescent retrograde tracing and fluorescence histochemistry. Stereotaxic microinjections of True Blue were placed in the central, caudal and lateral portions of the NRD, and after 6–12 days survival the brains were processed for fluorescence histochemical detection of catecholamines. Retrogradely labeled neurons were searched for in the diencephalic A11 and A13 dopaminergic cell groups, substantia nigra, ventral tegmental area (VTA) and the linear, central superior and dorsal raphe nuclei. The various NRD injections consistently resulted in retrograde labeling of a small number of catecholamine-containing, presumed dopaminergic cell bodies, confined mainly to three regions: the VTA, the linear and central superior raphe nuclei and the NRD itself. The present findings indicate that not only dopaminergic neurons in the VTA but also the system of catecholamine-containing cells, extending dorsally and caudally from the VTA within the midline raphe area, project to the NRD. Although often similar in size, shape and distribution to the catecholaminergic neurons the majority of retrogradely labeled cells in these regions were, however, found to be non-catecholaminergic.Abbreviations 3 Principal oculomotor nucleus - 4 Trochlear nucleus - Aq Cerebral aqueduct - cp cerebral peduncle - cst cortico-spinal tract - dscp decussation of the superior cerebellar peduncle - DTg Dorsal tegmental nucleus - fr fasciculus retroflexus - IF Interfascicular nucleus - IP Interpeduncular nucleus - LL nucleus of the lateral lemniscus - ml medial lemniscus - mlf medial longitudinal fasciculus - mNV mesencephalic trigeminal nucleus - NLC Nucleus linearis caudalis - NLR Nucleus linearis rostralis - NRD Dorsal raphe nucleus - PAG Periaqueductal grey - PN Pontine nucleus - PRN Pontine raphe nucleus - R Red nucleus - RCS Nucleus raphe centralis superior - SN Substantia nigra - VTA Ventral tegmental area - VTg Ventral tegmental nucleus     

Paraventricular nucleus magnocellular neuronal responses following electrical stimulation of the midbrain dorsal raphe

Summary In order to determine the responses of paraventricular nucleus magnocellular neurones following activation of central serotonergic pathways, single unit activity was recorded and responses following electrical stimulation of the midbrain dorsal raphe nucleus were examined. Approximately one third (32%) of the phasically active, vasopressin-secreting neurones were inhibited by the stimulation, the remaining such cells being nonresponsive. In contrast, only two of the non-phasic cells (13%) were inhibited by the stimulation whilst 53% were excited (p< 0.005, chi²-test). The onset latency of both inhibitory and excitatory responses were similar, whilst offset of the inhibitory responses was about twice that of the excitatory responses (p < 0.005, t-test). Two of the nonphasic cells were antidromically identified as projecting to the dorsal raphe. The results obtained indicate a role for dorsal raphe projections to the paraventricular nucleus in the regulation of neurohypophysial hormone secretion. The observation that different sub-populations of the cells recorded showed different responses, suggests that several mechanisms may be involved in the control of neuronal activity in the region recorded, in response to activation of the central serotonergic pathway examined. The results obtained are intended to further clarify the neural mechanisms regulating the secretion of vasopressin and oxytocin from the neurohypophysis.