A study of the organization of the locus coeruleus projections to the lateral geniculate nuclei in the albino rat

The lateral geniculate nuclei of the rat are known to receive an innervation from catecholamine-containing neurons. In the present study the origin, axonal projections and terminal distribution of this innervation was studied. The lateral geniculate nuclei contain a356 ± 20 ng norepinephrine/g and64 ± 7 ng dopamine/g tissue; the latter is within the range expected for dopamine as a precursor in a region innervated by a norepinephrine-containing terminal system. When separate norepinephrine-containing cell groups located at various brain stem levels are ablated or their axonal projections destroyed, only lesions in the locus coeruleus produce a significant decrease in the norepinephrine content of the lateral geniculate nuclei. Injections of horseradish peroxidase into the lateral geniculate nuclei result in retrograde transport of horseradish peroxidase only to the noradrenergic neurons of the locus coeruleus. The labelled neurons are pretent throughout the rostrocaudal and dorsoventral axes of both the ipsilateral (60%) and contralateral (40%) nucleus. Autoradiographic and fluorescence histo-chemical experiments indicate that axons that ascend from the locus coeruleus reach the lateral geniculate nuclei via the dorsal tegmental catecholamine-containing bundle and the medial forebrain bundle. These fibers enter the ventral lateral geniculate nucleus from the zona incerta and the dorsal lateral geniculate nucleus from the superior thalamic radiation, thalamic reticular nucleus, and lateral posterior nucleus. Contralateral fibers from the locus coeruleus cross in the posterior commissure, supraoptic and pontine decussations and join the ipsilateral projections to the lateral geniculate nuclei. The bilateral locus coeruleus innervation of the nuclei is comprised of a highly branched network of varicose axons. Neither the ipsilateral nor the contralateral projections appear to be topographically organized; instead, a single fiber may have collateral axons that branch throughout large areas of the nuclei. This innervation is moderately dense in the ventral, and very dense in the dorsal, lateral geniculate nucleus.The study indicates that both the dorsal and ventral lateral geniculate nuclei receive a diffuse catecholamine-containing innervation which arises solely from the norepinephrine-containing neurons of the locus coeruleus. The innervation of each lateral geniculate nucleus is bilateral, with noradrenergic neurons located throughout both the ipsilateral and the contralateral locus coeruleus contributing to ascending pathways that terminate as a diffuse, plexiform innervation interspersed among other afferents to the lateral geniculate nuclei. It is speculated that such a diffuse noradrenergic innervation might depress the spontaneous activity of neurons in the lateral geniculate nuclei, while preserving or enhancing their responsiveness to afferent optic stimulation.     

Neurons in the rat subiculum with transient postmamillary collaterals during development maintain projections to the mamillary complex

Summary We recently found that in developing rats large numbers of fibers extending through the fornix initially grow well past the mamillary bodies and into the mesencephalic and pontine tegmentum (Stanfield et al. 1987). This postmamillary component of the fornix is essentially completely eliminated during the first few postnatal weeks, although the cells of origin of this projection within the subicular complex of the hippocampal region persist. To determine if the subicular neurons which transiently extend postmamillary axons maintain a projection to the mamillary complex after the elimination of the postmamillary component of the fornix, we employed a delayed, double-retrograde labeling paradigm. The cells of origin of the postmamillary component of the fornix in rat pups were labeled with an injection of fast blue (FB) into the mesencephalic/pontine tegmentum, and, in the same animals, but at a stage after the elimination of the postmamillary component of the fornix, the cells of origin of the definitive fornix were labeled with an injection of diamidino yellow (DY) aimed at the mamillary complex. In these cases the FB labeled neurons within the subicular complex can be DY labeled as well, indicating that subicular neurons which transiently extend postmamillary axons maintain projections to the definitive targets of the fornix within the caudal hypothalamus.Abbreviations FB fast blue - DY diamidino yellow dihydrochloride - UV ultraviolet     

Spinal pathways mediating coeruleospinal antinociception in the rat

In a previous study, we showed in rats that axons of some locus coeruleus/subcoeruleus (LC/SC) neurons involved in coeruleospinal modulation of nociception descend through the ipsilateral side of the spinal cord and cross the midline at spinal segmental levels. The present study was designed to investigate a possible spinal pathway of these descending axons from the LC/SC. Extracellular recordings were made from the left dorsal horn with a carbon filament electrode (4-6 M(omega)). To block impulses from the LC/SC which descend through spinal pathways ipsilateral to the recording sites, a hemisection of the spinal cord ipsilateral to the recording sites was performed at the C2 level with fine forceps in all rats tested. In these rats, responses of dorsal horn neurons to noxious heat (53 degrees C) applied to receptive fields were inhibited during electrical stimulation (100 microA, 100 Hz, 0.1 ms pulses) of the LC/SC. The transection of the dorsolateral funiculus contralateral to the recording sites did not affect LC/SC stimulation-produced inhibition. Following transection of the ventrolateral funiculus (VLF) contralateral to the recording sites, LC/SC stimulation failed to inhibit heat-evoked responses. These results suggest that interruption of descending inhibition from the LC/SC produced by the VLF transections is due to the blockage of axons descending in the ventrolateral quadrant of the spinal cord, but not in the dorsolateral quadrant.     

Responses of locus coeruleus and subcoeruleus neurons to sinusoidal stimulation of labyrinth receptors

In precollicular decerebrate cats the electrical activity of 141 individual neurons located in the locus coeruleus-complex, i.e. in the dorsal (n = 41) and ventral parts (n = 67) as well as in the locus subcoeruleus (n = 33), was recorded during sinusoidal tilt about the longitudinal axis of the whole animal, leading to stimulation of labyrinth receptors. Some of these neurons showed physiological characteristics attributed to the norepinephrine-containing locus coeruleus neurons, namely, (i) a slow and regular resting discharge, and (ii) a typical biphasic response to fore- and hindpaw compression consisting of short impulse bursts followed by a silent period, which has been attributed to recurrent and/or lateral inhibition of the norepinephrine-containing neurons. Furthermore, 16 out of the 141 neurons were activated antidromically by stimulation of the spinal cord at T12 and L1, thus being considered coeruleospinal or subcoeruleospinal neurons. A large number of tested neurons (80 out of 141, i.e. 56.7%) responded to animal rotation at the standard frequency of 0.15 Hz and at the peak amplitude of 10 degrees. However, the proportion of responsive neurons was higher in the locus subcoeruleus (72.7%) and the dorsal locus coeruleus (61.0%) than in the ventral locus coeruleus (46.3%). A periodic modulation of firing rate of the units was observed during the sinusoidal stimulus. In particular, 45 out of the 80 units (i.e. 56.2%) were excited during side-up and depressed during side-down tilt (beta-responses), whereas 20 of 80 units (i.e. 25.0%) showed the opposite behavior (alpha-responses). In both instances, the response peak occurred with an average phase lead of about + 18 degrees, with respect to the extreme side-up or side-down position of the animal; however, the response gain (imp./s per deg) was, on average, more than two-fold higher in the former than in the latter group. The remaining 15 units (i.e. 18.7%) showed a prominent phase shift of this response peak with respect to animal position. Similar results were obtained from the subpopulation of locus coeruleus-complex neurons which fired at a low rate (less than 5.0 imp./s), as well as for the antidromically identified coeruleospinal neurons. The response gain of locus coeruleus-complex neurons, including the coeruleospinal neurons, did not change when the peak amplitude of tilt was increased from 5 degrees to 20 degrees at the fixed frequency of 0.15 Hz. This indicates that the system was relatively linear with respect to the amplitude of displacement.(ABSTRACT TRUNCATED AT 400 WORDS)     

Locus coeruleus projections to the dorsal motor vagus nucleus in the rat.

The origin of the noradrenergic innervation of the preganglionic autonomic nuclei in the medulla oblongata and spinal cord is still controversial. In this investigation descending connections of the locus coeruleus to the dorsal motor vagus nucleus in the rat are studied with Phaseolus vulgaris leucoagglutinin and horseradish peroxidase as neuroanatomical tracers. Locus coeruleus projections in the motor vagus nucleus are found in the medial part at rostral levels and in the lateral part at intermediate levels of this nucleus. The terminal labeling in the lateral intermediate part of the vagus nucleus appears in an area where possibly preganglionic parasympathetic cardiac neurons are located, suggesting that the locus coeruleus might be involved in regulation of cardiovascular functions. After small iontophoretic injections of horseradish peroxidase in the motor vagus nucleus, retrogradely labeled cells are found in the ventral part of the locus coeruleus and occasionally in the dorsal part of the nucleus. The results show that the locus coeruleus-dorsal motor vagus nucleus pathway may participate in the inhibition of the cardiac preganglionic neurons in the dorsal motor vagus nucleus by the hypothalamic paraventricular nucleus.     

Locus coeruleus neurons projecting to the forebrain and the spinal cord in the cat

The intranuclear organization of the cat locus coeruleus neurons was investigated anatomo-physiologically. The locus coeruleus neurons project to the forebrain through the dorsal noradrenergic bundle and to the spinal cord. Horseradish peroxidase, a retrograde tracer, was pressure-injected into either the dorsal noradrenergic bundle or the ventrolateral funiculus of the high cervical cord (C1-C2). The cats (n = 12) were killed after a 2- or 3-day survival period. The frontal sections (100 micron) throughout the locus coeruleus were observed by light microscope after carrying out the diaminobenzidine reaction. The labeled locus coeruleus neurons were located predominantly in the rostral locus coeruleus proper and locus coeruleus alpha when horseradish peroxidase was injected into the dorsal noradrenergic bundle, whereas they were predominantly located in the caudal locus coeruleus alpha and subcoeruleus when horseradish peroxidase was injected into the spinal cord. In the electrophysiological experiments, cats (n = 30) were anesthetized with alpha-chloralose and two stimulating electrodes were placed stereotaxically in the dorsal noradrenergic bundle and the ipsilateral ventrolateral funiculus of the high cervical cord (C1-C2), respectively. Monophasic square-wave pulses (2.5 Hz, 100 microsecond duration, 800 microA) were delivered. A recording glass electrode, filled with 2 M NaCl saturated with Fast Green, was placed in the locus coeruleus. Neurons with different conduction velocities, which were evoked by the antidromic stimulation of the dorsal noradrenergic bundle and spinal cord, were verified in the locus coeruleus and the adjacent areas. The slow conductive neurons with a conduction velocity of less than 1 m/s had a slow firing rate (1.6 +/- 0.9/s). They were located predominantly in the rostral locus coeruleus proper and locus coeruleus alpha by the dorsal noradrenergic bundle stimulation. From the anatomical and electrophysiological experimental results, it was concluded that the conduction velocities of the horseradish peroxidase-labeled neurons observed in locus coeruleus proper and locus coeruleus alpha were mostly slow and less than 1 m/s. Most of the slow conductive neurons were considered to be noradrenergic. Neurons evoked antidromically by both the dorsal noradrenergic bundle and spinal cord stimulation were not observed.     

Projections from the rat cuneiform nucleus to the A7, A6 (locus coeruleus), and A5 pontine noradrenergic cell groups

Stimulation of neurons in the cuneiform nucleus (CnF) produces antinociception and cardiovascular responses that could be mediated, in part, by noradrenergic neurons that innervate the spinal cord dorsal horn. The present study determined the projections of neurons in the CnF to the pontine noradrenergic neurons in the A5, A6 (locus coeruleus), and A7 cell groups that are known to project to the spinal cord. Injections of the anterograde tracer, biotinylated dextran amine in the CnF of Sasco Sprague-Dawley rats labeled axons located near noradrenergic neurons that were visualized by processing tissue sections for tyrosine hydroxylase-immunoreactivity. Anterogradely labeled axons were more dense on the side ipsilateral to the BDA deposit. Both A7 and A5 cell groups received dense projections from neurons in the CnF, whereas locus coeruleus received only a sparse projection. Highly varicose anterogradely labeled axons from the CnF were found in close apposition to dendrites and somata of tyrosine hydroxylase-immunoreactive neurons in pontine tegmentum. Although definitive evidence for direct pathways from CnF neurons to the pontine noradrenergic cell groups requires ultrastructural analysis, the results of the present studies provide presumptive evidence of direct projections from neurons in the CnF to the pontine noradrenergic neurons of the A7, locus coeruleus, and A5 cell groups. These results support the suggestion that the analgesia and cardiovascular responses produced by stimulation of neurons in the CnF may be mediated, in part, by pontine noradrenergic neurons.     

Cerebellar and spinal projections of the coeruleus complex in the duck: A fluorescent retrograde double-labeling study

The double fluorescent retrograde tracing technique was used to identify, within the coeruleus complex (Co complex) of the duck, the nerve cells projecting to the cerebellar cortex and to the spinal cord. This technique was also used to investigate the possibility that the cerebellar and spinal projections of the Co complex are collaterals of the same axons. In the same animal, nuclear Diamidino yellow dihydrochloride (DY) fluorescent tracer was placed into the cerebellar cortex of folia V–VII, and cytoplasmic fluorescent Fast blue (FB) dye was injected into C₃–C₄ spinal cord segments. FB labeled multipolar somata and DY fluorescent nuclei were intermingled within the dorsal caudal region of the locus coeruleus (LCo) and within the dorsal division of the nucleus subcoeruleus (dSCo). Moreover, in the LCo, a low proportion of double-labeled neurons (about 3–4% of labelings) was evidenced among single-labeled neurons. In the ventral division of the nucleus subcoeruleus (vSCo), occasional DY labeled nuclei were found, whereas FB-labeled cells were frequently present. The present findings reveal the location of the coeruleocerebellar and coeruleospinal projecting neurons within the Co complex of the duck. They are intermingled in the caudal portion of the LCo and along the rostrocaudal extent of the subjacent dSco. The LCo and the dSCo are the major source of the projections to the folia V–VII, whereas the vSCo contributes very slightly to the innervation of the cerebellar injected areas. Moreover, the double-labeling study demonstrates that in the duck a low percentage of neurons within the ventrolateral portion of the caudal region of the LCo projects both to the cerebellar cortex of folia V–VII and to C₃–C₄ spinal cord segments via collaterals. Therefore, these neurons simultaneously influence the cerebellar cortex and spinal cord. The possibility that the projections studied are noradrenergic and that they play a role in feeding is discussed. Anat. Rec. 251:392–397, 1998. © 1998 Wiley-Liss, Inc.     

Locus coeruleus neurons in the rat containing neuropeptide Y, tyrosine hydroxylase or galanin and their efferent projections to the spinal cord, cerebral cortex and hypothalamus

The efferent projections of locus coeruleus neurons which contain neuropeptide Y-, tyrosine hydroxylase- or galanin-like immunoreactivity were investigated using the indirect immunofluorescence technique combined with the retrograde transport of the fluorescent substance Fast Blue. Four groups of rats received injections of Fast Blue: (1) bilaterally into the mid-thoracic spinal cord (T6-T7); (2) unilaterally into the low cervical spinal cord (C4-C5); (3) unilaterally into the paraventricular, periventricular and dorsomedial hypothalamic nuclei; and (4) unilaterally into five sites in the cerebral cortex (frontal, cingulate and striate cortex). Efferent projections to the spinal cord, hypothalamus and cerebral cortex from neuropeptide Y-, tyrosine hydroxylase- and galanin-containing locus coeruleus cells were observed. A higher percentage of the peptidergic locus coeruleus neurons projected to the hypothalamus than to the spinal cord or cerebral cortex. The distribution and morphology of the neuropeptide Y- and galanin-containing neurons in the locus coeruleus were also investigated. Neuropeptide Y-like immunoreactivity and galanin-like immunoreactivity were found in small, medium and large multipolar neurons, as well as in fusiform locus coeruleus cells. The neuropeptide Y- and galanin-immunoreactive neurons were found throughout the locus coeruleus. In the caudal locus coeruleus, they were primarily located in the dorsal portion. Neuropeptide Y-like immunoreactivity and galanin-like immunoreactivity were only seen in a few tyrosine hydroxylase-positive neurons of the subcoeruleus group. The data show that the peptide-containing locus coeruleus neurons have efferent projections to the spinal cord, hypothalamus and cerebral cortex. The locus coeruleus may be divided into functional subdivisions dependent on the region of the locus coeruleus, the neurotransmitter/neuropeptide(s) contained within the neurons and their efferent projections.     

Reactive changes in dorsal roots and dorsal root ganglia after C7 dorsal rhizotomy and ventral root avulsion/replantation in rabbits

Current surgical treatment of spinal root injuries aims at reconnecting ventral roots to the spinal cord while severed dorsal roots are generally left untreated. Reactive changes in dorsal root ganglia (DRGs) and in injured dorsal roots after such complex lesions have not been analysed in detail. We studied dorsal root remnants and lesioned DRGs 6 months after C7 dorsal rhizotomy, ventral root avulsion and immediate ventral root replantation in adult rabbits. Replanted ventral roots were fixed to the spinal cord with fibrin glue only or with glue containing ciliary neurotrophic factor and/or brain-derived neurotrophic factor. Varying degrees of degeneration were observed in the deafferented dorsal spinal cord in all experimental groups. In cases with well-preserved morphology, small myelinated axons extended into central tissue protrusions at the dorsal root entry zone, suggesting sprouting of spinal neuron processes into the central dorsal root remnant. In lesioned DRGs, the density of neurons and myelinated axons was not significantly altered, but a slight decrease in the relative frequency of large neurons and an increase of small myelinated axons was noted (significant for axons). Unexpectedly, differences in the degree of these changes were found between control and neurotrophic factor-treated animals. Central axons of DRG neurons formed dorsal root stumps of considerable length which were attached to fibrous tissue surrounding the replanted ventral root. In cases where gaps were apparent in dorsal root sheaths, a subgroup of dorsal root axons entered this fibrous tissue. Continuity of sensory axons with the spinal cord was never observed. Some axons coursed ventrally in the direction of the spinal nerve. Although the animal model does not fully represent the situation in human plexus injuries, the present findings provide a basis for devising further experimental approaches in the treatment of combined motor/sensory root lesions.     

Immunoelectron microscopic localization of E-cadherin in dorsal root ganglia, dorsal root and dorsal horn of postnatal mice

Summary Sensory neurons and associated glial cells are known to express the cell-cell adhesion molecule E-cadherin. The cellular and subcellular localization of this molecule in the dorsal root ganglion, dorsal root, and spinal cord of postnatal mice was studied by the pre-embedding immunoelectron microscopic labelling technique. In the dorsal root and the superficial layer of the dorsal horn, a subset of fasciculating unmyelinated axons expressed E-cadherin at their axon-axon contacts at all ages studied, and these axons were clustered together and segregated from E-cadherin-negative axons. In contrast, pre-myelinating large-diameter axons in P2 mice as well as myelinated axons in mice from P14 to adulthood were E-cadherin-negative. Glial cells also expressed E-cadherin: In the dorsal root ganglia, all of the satellite cells expressed E-cadherin at contact sites with neurons, other satellite cells, and basal lamina, at all ages studied. In dorsal roots from P14 to adulthood, myelin-forming Schwann cells expressed E-cadherin at the outer mesaxons and the contact sites with basal lamina. Non-myelin-forming Schwann cells occasionally stained for this molecule at contact sites with the plasma membrane of E-cadherin-positive axons and at other sites. These results strongly suggest that E-cadherin plays an important role in the selective fasciculation of a particular subset of unmyelinated sensory fibres, and also in glial cell contacts.     

The distribution of hippocampal and spinal projecting cells in the locus coeruleus of tottering mice

Wheat germ agglutinin conjugated to horseradish peroxidase and Fast Blue were used as retrograde tracers to examine the distribution of coeruleohippocampal and coeruleospinal somata within the locus coeruleus of normal and tottering mutant mice. The distributions of these projection neuron populations in normal mice are similar to what has been found in other species, and the distributions of these projection neurons in tottering mice are indistinguishable from those in normal mice, in spite of the norepinephrine hyperinnervation of certain locus coeruleus targets, including the hippocampus, in the tottering mutant. These observations lend support to the notion that the defect in tottering acts fairly directly on mechanisms involved in the development of locus coeruleus axonal arbors within certain target regions.     

Cell suspension grafts of noradrenergic locus coeruleus neurons in rat hippocampus and spinal cord: reinnervation and transmitter turnover

Fetal noradrenergic neurons from the brain stem locus coeruleus region can be successfully grafted as a dissociated cell suspension provided that the dissociation is done in the absence of any trypsin digestion step. The survival, fiber outgrowth and biochemical function of locus coeruleus neurons, taken from 13- to 15-day-old rat embryos, have been studied after injection into the dorsal hippocampal formation and the thoracolumbar spinal cord in adult rats. All rats were treated with an i.v. injection of 6-hydroxydopamine prior to grafting to remove the intrinsic locus coeruleus projections to these areas, and they were taken for fluorescence histochemical or biochemical analyses 2-7 months after transplantation. Up to 330 surviving noradrenaline neurons were found at each implantation site (injected with 2-3 microliters of cell suspension) which represents an estimated survival rate of about 40%. In the most successful cases the entire dorsal hippocampal formation, and an approximately 4 cm long segment of the thoracolumbar spinal cord, was supplied with a new noradrenaline-containing terminal network, which reached normal densities in the regions closest to the grafts. In the hippocampal formation, in particular, the ingrowing axons re-established a laminar innervation pattern which resembled that of the normal locus coeruleus afferents. In the hippocampus, two 2-microliters injections of locus coeruleus cell suspension restored the total hippocampal noradrenaline content to an average of 55%, and the noradrenaline synthesis rate (as assessed by the rate of DOPA accumulation after synthesis inhibition) was found to be close to normal in the graft-reinnervated specimens. In the spinal cord, two 3-microliters injections restored the noradrenaline level in the thoracolumbar cord (a 4.5 cm long segment) to an average of 22% of normal, with the highest individual levels being close to normal. Determinations of the noradrenaline metabolite 3,4-dihydroxy-phenylethyleneglycol indicated that the rate of noradrenaline metabolism in the graft-reinnervated spinal cord was close to that of the normal intact spinal cord. The results demonstrate the potential of the suspension grafting technique for extensive noradrenergic reinnervation of the hippocampal formation or large portions of the spinal cord. Fetal locus coeruleus neurons implanted in this way can re-establish fairly normal terminal innervation patterns and reinstate noradrenaline turnover and metabolism in a previously denervated central target.     

Norepinephrine innervation of the cochlear nuclei by locus coeruleus neurons in the rat

Summary The cochlear nuclei (CN) contain a moderate concentration of norepinephrine (445±20 ng/g tissue) with dopamine levels (46±14 ng/g) that are low and within the precursor range expected for a norepinephrine (NE) terminal system. Lesion and horseradish peroxidase (HRP) experiments indicate that this innervation is bilateral and arises from fusiform and multipolar neurons in the locus coeruleus.Autoradiographic and fluorescence histochemical experiments demonstrate that locus coeruleus fibers reach the ipsilateral ventral cochlear nuclei via a rostral pathway that projects from the rostral locus coeruleus laterally through the brain stem to the rostral tip of the ventral nuclei. This pathway is located dorsal to the motor and spinal trigeminal nuclei and ventral to the middle cerebellar peduncle. Descending coeruleo-cochlear fibers travel between the fourth ventricle and the vestibular nuclei to enter the acoustic striae. These fibers innervate both the dorsal and ventral nuclei. Contralateral locus fibers reach the CN by crossing in the pontine central gray at the rostral border of the fourth ventricle and by decussating with the fibers of the mesencephalic trigeminal nucleus ventral to the medial longitudinal fasciculus. The bilateral locus coeruleus innervation of the cochlear nuclei comprises a highly collateralized network of varicose axons which are not topographically organized. Unlike the cochlear nerve fibers in the CN which form specific projections, the locus coeruleus afferents to these sensory nuclei are diffuse and non-specific.     

Estrogen receptor-alpha immunoreactive neurons in the brainstem and spinal cord of the female rhesus monkey: species-specific characteristics

The distribution pattern of estrogen receptors in the rodent CNS has been reported extensively, but mapping of estrogen receptors in primates is incomplete. In this study we describe the distribution of estrogen receptor alpha immunoreactive (ER-alpha IR) neurons in the brainstem and spinal cord of the rhesus monkey. In the midbrain, ER-alpha IR neurons were located in the periaqueductal gray, especially the caudal ventrolateral part, the adjacent tegmentum, peripeduncular nucleus, and pretectal nucleus. A few ER-alpha IR neurons were found in the lateral parabrachial nucleus, lateral pontine tegmentum, and pontine gray medial to the locus coeruleus. At caudal medullary levels, ER-alpha IR neurons were present in the commissural nucleus of the solitary complex and the caudal spinal trigeminal nucleus. The remaining regions of the brainstem were devoid of ER-alpha IR neurons. Spinal ER-alpha IR neurons were found in laminae I-V, and area X, and were most numerous in lower lumbar and sacral segments. The lateral collateral pathway and dorsal commissural nuclei of the sacral cord and the thoracic intermediolateral cell column also contained ER-alpha IR neurons. Estrogen treatment did not result in any differences in the distribution pattern of ER-alpha IR neurons. The results indicate that ER-alpha IR neurons in the primate brainstem and spinal cord are concentrated mainly in regions involved in sensory and autonomic processing. Compared with rodent species, the regional distribution of ER-alpha IR neurons is less widespread, and ER-alpha IR neurons in regions such as the spinal dorsal horn and caudal spinal trigeminal nucleus appear to be less abundant. These distinctions suggest a modest role of ER-alpha in estrogen-mediated actions on primate brainstem and spinal systems. These differences may contribute to variations in behavioral effects of estrogen between primate and rodent species.     

神经元核抗原在大鼠中枢神经系统神经元的不同表达

目的观察正常大鼠中枢神经系统(CNS)内神经元核抗原(NeuN)的表达。方法正常成年SD大鼠5只,常规固定,恒冷箱切片,免疫组织化学、免疫荧光染色、尼氏染色。结果NeuN在成年大鼠CNS神经元有4种表达:大部分神经元(大脑皮质、基底核、脊髓背角等)有明显表达;部分神经元为中等表达(三叉神经脊束核、下丘脑室旁核等);部分神经元为弱表达(孤束核、蓝斑等);而有些核团神经元缺乏NeuN的表达(视上核、弓状核、迷走神经背核等)。结论中枢神经系统不同区域或核团的神经元NeuN的表达程度不同,有的区域或核团神经元缺乏NeuN表达。     

Locus coeruleus terminals in intraocularly transplanted spinal cords as compared with catecholamine terminals in normal spinal cords: Their synaptic densities and functional considerations

Locus coeruleus terminals in intraocularly transplanted spinal cords and catecholamine terminals in defined areas of normal spinal cords were investigated qualitatively and quantitatively by immunoelectron microscopy. Results showed that the morphological features of synapses formed in the grafts closely resembled those of normal spinal cords. The incidences of synapses per varicosities, as observed in single sections, were 30.1, 40.2 and 22.8% for the ventral horn, dorsal horn and grafted spinal cord, respectively. In all three groups, most of the postsynaptic targets were small dendrites, although high frequencies of large dendrites were found in the ventral horn. Spines and axons in the grafts were also postsynaptic targets. Several characteristics of relative immaturity were observed in the grafts. It is suggested that the inhibition of spinal neurons by locus coeruleus terminals may be mediated not only by volume transmission through nonsynaptic contacts, but also by direct contacts with catecholamine terminals, and that the excitation of facilitation observed at those terminals may be explained by the suppression of inhibitory neurons by axoaxonic contacts.     

Regrowth of lesioned dorsal root nerve fibers into the spinal cord of neonatal rats

In postnatal rat pups the L4 and L5 dorsal roots were lesioned. After 3-6 months the spinal cord of the rats was subjected to tracing studies of regenerated dorsal root axons with transganglionically transported horseradish peroxidase (HRP) and immunohistochemistry with antibodies to calcitonin gene-related peptide (CGRP). In rats operated at birth (0-2 days old) HRP-filled profiles as well as CGRP staining were found in the outer lamina of the spinal cord dorsal horn. Signs of dorsal root nerve fiber regrowth in the spinal cord could not be found in rats which had been operated at the end of the first postnatal week or later.     

人胎蓝斑神经元免疫组织化学研究

为了探讨人蓝斑神经元的胚胎发育特征 ,为蓝斑 -脊髓移植选择适宜胎龄提供形态学根据 ,本研究用免疫组织化学技术系统地观察了人胎蓝斑酪氨酸羟化酶样免疫反应阳性神经元的发育。结果证明 :( 1)蓝斑酪氨酸羟化酶样神经元在胎龄 4个月时已经出现在蓝斑的腹侧部 ;( 2 )蓝斑酪氨酸羟化酶样神经元随胎龄增长逐渐增多 ,以 5个月时增加显著 ;( 3)酪氨酸羟化酶样神经元的密度在胚胎早期升高 ,晚期呈下降趋势 ;( 4)酪氨酸羟化酶样神经元主要分布在蓝斑的背侧部 ,少量散在于腹侧部 ;( 5)酪氨酸羟化酶样神经元开始出现时呈圆形或卵圆形 ,5～ 6个月时呈锥形和梭形 ,7～ 8个月时则以梭形、多角形为主。其胞体逐渐增大 ,胞浆逐渐增多 ,核浆之比由大变小 ,胞突从粗短变为细长平滑。本研究结果提示 ,人胎蓝斑移植以 4个月胎龄者作移植供体较为适宜