摘要:

AbstractThe medial preoptic area (MPO), a sexually dimorphic region, plays a pivotal role in neuroendocrine function and reproductive behavior. We recently reported that MPO projects heavily to the midbrain periaqueductal gray (PAG). We also noted that MPO projects to the dorsolateral pontine tegmentum. Here we identified the cells of origin of the MPO→tegmental projection and delineated the terminal organization of MPO projections to Barrington's nucleus, locus coeruleus (LC), and the rostromedial pericoerulear region (pLCrm). Correlative cyto‐ and chemoarchitectonic studies were done to define better the nuclear groups of the dorsolateral pontine tegmentum.Retrograde tracing revealed that MPO neurons projecting to the dorsolateral pontine tegmentum are preferentially distributed in distinct subregions of MPO, including the sexually dimorphic medial preoptic nucleus (MPN). Anterograde tracing with wheat germ agglutininhorseradish peroxidase orPhaseolus vulgarisleucoagglutinin demonstrated considerable target specificity in projections from MPO to the dorsolateral pontine tegmentum. Barrington's nucleus receives a dense focal input along its entire rostrocaudal axis. In addition, pLCrm is heavily targeted by MPO inputs; pLCrm contains a concentrated plexus of extranuclear dendrites of LC neurons. The lateral dorsal tegmental (LDT) nucleus and LC proper receive only sparse input from MPO.MPO projections to Barrington's nucleus could regulate micturition reflexes during reproductive behavior. The MPO→pLCrm projection could influence noradrenergic LC neurons in relation to reproductive and/or gonadal steroid function. Given the strong established connections from olfactory structures to MPO, it is possible that the MPO→LC pathway provides an anatomical substrate for olfactory modulation of arousal. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903470102

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA combination of retrograde tracers was used to compare the relative distributions of motoneurons supplying the ventral and lateral suboccipital muscles, rectus capitis anterior (RCA), and rectus capitis lateralis (RCL), with those supplying dorsal muscles, including rectus capitis posterior muscles (RCP), complexus (CM), and the medial head of obliquus capitis superior (OCS). Three of the tracers, horseradish peroxidase, fluororuby, and fluoresceinconjugated dextran, were applied to cut nerve ends. Fast blue was applied by intramuscular injection, and fluorogold was delivered both by injection and by cut nerve exposure. Motoneurons supplying RCA and RCL were clustered on the medial wall of the ventral horn in a restricted region defined previously as the commissural nucleus. Labelled cells supplying RCL were confined to the C1 segment, but those supplying RCA were distributed from C1 to rostral C4. Motoneurons supplying RCA tended to lie more dorsomedially than those supplying RCL, but there was substantial overlap between the two populations. Motoneurons supplying dorsal muscles had a separate, more ventral distribution. RCP motoneurons were located primarily in the ventromedial nucleus, but a small proportion of cells was found in the white matter of the ventral funiculus or the gray matter surrounding the central canal. Motoneurons supplying CM and OCS were located dorsomedially to the RCP cell population. These results suggest that neck motoneurons are arranged according to a “musculotopic” pattern in which dorsal muscles have the most ventral locations, and progressively more lateral and then ventral muscles are layered dorsomedially along the medial wall of the ventral horn. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903470103

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractNumerous studies have shown in the adult nervous system that mRNA expression can be regulated by neuronal activity. To examine the effect of activity during embryogenesis, the ontogeny of proenkephalin mRNA expression and expression following activity blockade was investigated during development of chick spinal cord. A cDNA fragment (ca. 0.5 kb) coding for chick proenkephalin was cloned and sequenced. With this cDNA, a cRNA probe was made to examine proenkephalin mRNA expression in the spinal cord during embryogenesis. Proenkephalin mRNA was expressed in spinal cord in clusters of cells located in the developing dorsal horn and intermediate lamina at the earliest stages examined (stage 22; E4). Proenkephalin‐positive cells in the intermediate lamina were located immediately adjacent to the ventricular zone. At stage 28 (E6) an additional cluster of proenkephalin mRNA‐positive cells was seen at the lateral border of the developing intermediate lamina. At stage 33 (E7. 5–8) the pattern of hybridization positive cells was similar to earlier stages, but individual cells could be identified. At stage 39 (E13) densely labeled cells were seen throughout the dorsal horn and intermediate laminae including the column of Terni. To determine whether neural activity affects proenkephalin mRNA expression,d‐tubocurarine (an inhibitor of neural activity) was injected into developing embryos. Following administration ofd‐tubocurarine a dramatic decrease was seen in proenkephalin mRNA hybridization in the dorsal horn and intermediate lamina of the spinal cord. This study demonstrates in vivo that changes in the level of neural activity can alter gene expression during embryogenesis and suggests that activity is required for expression of nervous system‐lspecific genes. © 1994 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903470104

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have studied the morphology of silver‐impregnated neurons (rapid Golgi technique) in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), a center involved in the control of vertical and torsional saccadic eye movements. This morphological study of riMLF neurons in the rhesus monkey was undertaken to further our understanding of the functional circuitry of the oculomotor system. Our study employed Nissl, Golgi, and computer‐ assisted methods. The cytoarchitectonic boundaries of the riMLF and its relationships to neighboring structures were determined in both Nissl and Golgi preparations. Five (I–V) distinct morphological types of riMLF neurons were distinguished in the Golgi impregnations on the basis of soma size, dendritic size, numbers of primary dendrites, number of dendritic branch points, as well as form, number, and distribution of dendritic appendages. Type I neurons impregnated most frequently and had the most extensive and highly branched dendritic tree. Type II neurons displayed thick dendrites with complex dendritic appendages, but the dendritic tree was much more compact than that of type I cells. Type III and type V cells had fusiform somas and relatively unbranched dendritic trees but differed greatly in size as well as dendritic morphology. The type IV cell was the smallest neuron and had many characteristics of the local interneurons found in other thalamic, subthalamic, hypothalamic, and midbrain centers. The type V was the largest neuron, least frequently impregnated, and found only at rostral riMLF levels. Digitized reconstructions of each type of neuron were rotated by the computer, which revealed that the dendritic trees of types I, III, and V occupy a disk‐like compartment in the riMLF neuropil. In contrast, the trees of types II and IV occupy a roughly spherical compartment. We suggest that three of the cell types are well suited for specific purposes: type II cells for receiving, topographically organized inputs that contain spatial information, type I cells for short‐lead burst neuron output to the motor neurons or other premotor centers, and type IV cells for inhibitory inputs to type I cells. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903470105

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractContraction of the diaphragm is controlled by phrenic motoneurons that receive input from sources that are not fully established. Bulbospinal (second‐order) neurons projecting to phrenic motoneurons and propriobulbar (third‐order) neurons projecting to these bulbospinal neurons were investigated in rat by transsynaptic transport of the neuroinvasive pseudorabies virus. Bulbospinal neurons were located predominantly in the medullary lateral tegmental field in two functionally described regions, the ventral respiratory group and Bötzinger complex. An intervening region, the pre‐Bötzinger complex, contained essentially no phrenic premotoneu rons. Bulbospinal neurons were also located in ventral, interstitial, and ventrolateral subnuclei of the solitary tract, and gigantocellular, Kölliker‐Fuse, parabrachial, and medullary raphe nuclei. A monosynaptic pathway to phrenic motoneurons from the nucleus of the solitary tract was confirmed; monosynaptic pathways from upper cervical, spinal cord, spinal trigeminal nucleus, medial and lateral vestibular nuclei, and medial pontine tegmentum were not verified. Locations of third‐order neurons were consistent with described projections to the ventral respiratory group, from contralateral ventral respiratory group, Bötzinger complex, A5 noradrenergic cell group, and the following nuclei: solitary, raphe, Kölliker‐Fuse, parabrachial, retrotrapezoid, and paragigantocellular. Novel findings included a projection from locus coeruleus to respiratory premotoneurons and the lack of previously described pathways from area postrema and spinal trigeminal nucleus. These second‐ and third‐order neurons form the output network for diaphragm motor control which includes numerous behaviors (e. g., respiration, phonation, defecation). Of the premotoneurons, the rostral ventral respiratory group is the primary population controlling phrenic motoneurons. ©

ISSN:0092-7317    

DOI:10.1002/cne.903470106

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study attempts to determine whether fetal thalamic neuroblasts from rat embryos (embryonic age 15 days) labeled with horseradish peroxidase (HRP) can differentiate into their normal dendriticphenotype when transplanted as a cell suspension into a lesioned site in the adult somatosensory thalamus. The HRP labeling provided a Golgi‐like staining of numerous neurons up to 12–14 days after transplantation. There were three main results. (1) As early as 2 days after transplantation three morphologic cell types were observed: Two were bipolar and the third multipolar. These cellular profiles are characteristic of adult ventroposterolateral, reticular, and ventroposteromedial neurons and suggest that transplanted neurons can take shape in the absence of specific arrangements of afferent fibers. (2) The initial stage of dendritic growth was characterized by numerous growing specializations and consisted of a rapid, arborizing growth that appeared to proceed at an accelerated rate relative to normal development. During the later stage, which was characterized by the great reduction of growing specializations, dendritic remodeling resulted in a simpler morphology, and the transplanted neurons did not achieve an adult morphology. (3) Putative axons exhibiting growth cones were present in impressive densities in the transplants, and a number of them grew into the neuron‐depleted host thalamus. A very small number of axons grew into host gray matter outside the lesioned area, indicating that neurodegenerative areas provide a better substrate for neurite outgrowth than, intact tissue. In rare instances axons were visible in the internal capsule, indicating that the biochemical inhibition provided by mature myelin and oligodendrocytes may not be an absolute obstacle to axonal growth. © 1994 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903470107

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractAlthough the general patterns of the developing histaminergic system in the rat brain are known, no comparative studies between the development of the brain histaminergic system and the development of other neuroactive substances have yet been published. Interestingly, separate immunohistochemical studies on the development of the 5‐HT system and on the catecholaminergic system in the rat imply common features in the different aminergic systems. Therefore, the spatial distribution of histamine‐immunoreactive (HA‐ir) neurons and nerve fibers was compared to the distribution of 5‐hydroxytryptamine (5‐HT)‐, and tyrosine hydroxylase‐immunoreactive (TH‐ir) ones in the developing rat brain between embryonic days 12, (E12) and 20 (E20) by using a double‐immunostaining method. The high‐pressure liquid chromatography (HPLC) fluorometric method was used for determination of histamine concentration in different brain regions during the same period of development and synthetic oligonucleotide probes complementary to the rat histidine decarboxylase (HDC) to determine the origin of HA in the brain during the development with in situ hybridization. The immunohistoch6mical results revealed co‐localization of HA and 5‐HT within a subgroup of cells in the developing raphe nuclei between E14 and E18. From E18 onwards HA immunoreactivity started to gradually disappear from the rhombencephalon, and was totally abolished by E20, while 5‐HT‐ir cells continued to establish their adult positions. No significant colocalization of RA and TH immunoreactivities was detected. The biochemical results were in agreement with the immunohistochemical ones and confirmed that histamine detected in the early developing brain is authentic. A positive in situ hybridization signal for HDC was detected in a small area in the ventrolateral pons in the same areas as HA‐ and HDC‐ir cell bodies at E16, suggesting that at least some HA may be synthesized locally. These results confirm that HA is one of the first neurotransmitters to appear in the developing brain. In addition, the transient co‐localization of HA and 5‐HT immunoreactivities and the transient HDC expression at E16 within the developing pontine raphe nuclei may imply an interesting and a more general role for HA in modification of brain

ISSN:0092-7317    

DOI:10.1002/cne.903470108

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe postnatal development of rat corticospinal motor neurons (CSMN) was studied by retrograde tracing with cholera toxin B subunit (CTB) injected into the upper cervical dorsal spinal cord on the first postnatal day (P0), P3, P10, P20, and at adulthood. CTB‐labeled neurons were visualized by immunocytochemistry and extensively quantified throughout the cortex. At P0, CSMN were found to an extent similar to that reported in P3 animals with other neuronal tracers, now permitting in vitro studies of neonatal CSMN. Between P0 and P3, the number of labeled neurons increased by 30% to a total maximum of approximately 185,000 in both cortices. The increase occurred throughout the cortex. At P10, the number of labeled CSMN had decreased to 60% of the number at P3. Fewer CSMN were evident particularly in the perirhinal cortex. Between P10 and P20, the number of CSMN decreased further to 52% of the maximal number at P3. This decrease occurred predominantly in the cingulate and parietal cortex. The number of labeled CSMN in rats injected at P0 and analyzed at P20 was 10% lower than the number in P0‐injected littermates that were analyzed at P3, which suggests that only a small portion of the “disappearing” CSMN undergoes developmental neuronal death. Thus, the spinal projection of the remaining 38% is apparently eliminated between P3 and P20. Detailed quantitative analysis of the CSMN distribution demonstrated that neuronal death occurs predominantly in the perirhinal cortex. In contrast, axonal elimination of corticospinal projections occurred throughout the CSMN field, i. e., primarily in the frontal, occipital, and perirhinal cortex between P3–P10 and in the cingulate and parietal cortex between P10–P20. © 1994 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903470109

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTo further characterize the communication between the thalami of the two hemispheres, a connection linking the rostral reticular nuclei of the two thalamic sides was investigated in the rat by retrograde and anterograde tracing. The rostral reticular nucleus can be divided into a medial region, with densely packed fusiform neurons, and a lateral region, with less densely packed, polymorphic neurons. After injections of Fluorogold (FG) in the medial region, retrogradely labeled, small fusiform neurons were found in the corresponding contralateral region. The retrograde labeling data were confirmed by the anterograde‐tracing experiments. Thin, beaded axons, anterogradely labeled after injection of biocytin or biotinylated dextranamine in the medial region, innervate the corresponding region in the contralateral reticular nucleus.The present data suggest the existence of a commissural pathway specifically devoted to the crosstalk between the rostral reticular nuclei of the two thalamic sides. The commissural gamma aminobutyric acid (GABA)‐ergic input on the GABAergic neurons of the rostral reticular nucleus could modulate the generation of sleep spindles. The reticuloreticular pathway may, moreover, synchronize the diffuse modulatory effect of the rostral reticular nucleus on nonprimary cortical areas through the bilateral projections of the nucleus to the ventromedial, intralaminar, and anterior thalamic nuclei. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903470110

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the mammalian retina, rod signals are transmitted by rod bipolars to the narrow‐field, bistratified (AII) amacrine cell. This neuron, in turn, makes gap junctions with the axonal arborization of cone bipolar cells that reside in the vitreal half (sublaminab) of the inner plexiform layer (IPL). After examining rod bipolars and AII amacrines in the rabbit retina, we have now reconstructed from electron micrographs of continuous series of thin sections the synaptic connections of the axonal arborizations of cone bipolar cells that make the highest number of gap junctions with AII amacrines.These axonal arborizations were narrowly confined to stratum 4 (S4) of the IPL and made ribbon synapses to dyads of postsynaptic‐dendrites that belonged to either ganglion or amacrine cells. In the population of postsynaptic processes, 30% were ganglion cell dendrites. These dendrites were probably originating, at least in part, fromon‐center ganglion cells because their course was confined to sublaminabof the IPL. Of the remaining postsynaptic processes, 51.7% belonged to amacrine cells and 18.3% were not identified. Among the postsynaptic amacrine cell processes, 33.3% returned a reciprocal synapse onto the cone bipolar endings. These reciprocal synapses represented 21.3% of the total input onto the axonal arborizations, the remaining fraction (78.7%) arising from a heterogeneous population of amacrine dendrites that were purely presynaptic to the cone bipolars endings. Pre‐ and postsynaptic amacrines were part of several distinct microcircuits which suggest complex local processing of both rod and cone signals.Thus, the cone bipolars that make gap junctions with AII amacrines in sublaminabof the rabbit IPL exhibit a substantial output onto ganglion cells. This fact, in conjunction with our previous observations that in this sublamina ganglion cells receive negligible input from rod bipolars and AII amacrines, demonstrates that in the rabbit cone bipolars represent a necessary link in the pathway followed by rod signals to enteron‐center ganglion cells. Thus, rod and cone signals ultimately share the same integrating mechanisms and converge onto the same set of ganglion cells. © 1994 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903470111

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY