摘要:

AbstractImmunohistochemical studies in several mammalian species and in red‐eared turtles have shown that somatostatin (SS) and neuropeptide Y (NPY) co‐occur in a substantial proportion of the telencephalic neurons containing either. To explore further the possibility that telencephalic neurons co‐containing SS and NPY may be evolutionarily conserved among amniotes, we determined the distribution and co‐occurrence of SS and NPY in forebrain neurons in pigeons. Single‐label immunohistochemical studies revealed the presence of overlapping populations of SS + neurons and NPY+ neurons in most of the major subdivisions of the telencephalon. Double‐label immunofluorescence studies revealed that in subdivisions of the telencephalon that are comparable to mammalian cortex (i.e., those dorsal and lateral to the basal ganglia), the vast majority of NPY+ neurons were also SS+, whereas a major and regionally variable percentage of the SS+ neurons were not NPY+. In contrast, within the basal telencephalon (including the basal ganglia and several other structures) neurons labeled only for NPY or only SS were more abundant than those containing both neuropeptides. Outside the telencephalon, the only forebrain cell group containing neurons in which SS and NPY were co‐localized was in the lateral hypothalamus.A series of double‐ and triple‐label immunohistochemical studies was undertaken to determine the extent of co‐occurrence of SS and NPY in striatal neurons and the relationship of these neurons to striatal neurons containing other neuropeptides. In addition, immunohistochemical single‐ and double‐label techniques were employed in conjunction with retrograde‐labeling by fluorogold to determine the projections of SS+ and NPY+ striatal neurons. The results indicate that: (1) a population of striatal interneurons containing both SS and NPY exists in pigeons and constitutes approximately the same fraction of all striatal neurons as reported in mammals, (2) neurons containing NPY (but not SS) form a second, larger population of striatal interneurons, (3) neurons containing SS (but not NPY) form a third population of striatal interneurons that is approximately half as abundant as the NPY+ interneuron population, and (4) one‐third of the substance P‐containing striatonigral projection neurons also contain SS.The existence in pigeons of a major population of neurons containing both SS and NPY throughout the telencephalon, the existence of a population of neurons containing only SS in cortex‐equivalent parts of the telencephalon, and the existence of a population of interneurons containing only NPY in the striatum is consistent with findings in mammals and turtles. The existence of these peptide‐specific populations in members of each class of amniotes favors the view that these populations were present in the last common ancestor of amniotes and were conserved during amniote evolution. Thus, they most likely play fundamentally important roles in telencephalic circuits. However, the avian striatum contains a substantial population of SS+ interneurons and a population of SS+/SP+ striatonigral projection neurons. SS+ projection neurons have also been reported in the guinea pig, but not in other mammals. Thus, the presence of some types of SS‐containing stri

ISSN:0092-7317    

DOI:10.1002/cne.902990302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractAs part of an attempt to understand the spinal control of the segmented axial musculature in goldfish, commissural spinal interneurons that are electrotonically coupled to the Mauthner axon (M‐axon) were studied with intracellular recording and staining to examine their morphology, segmental relationships, and functional role. Prior studies suggested that these cells might mediate the crossed inhibition that blocks excitation of motoneurons on one side of the body during an escape bend to the opposite side. Simultaneous intracellular recordings from a M‐axon, a commissural interneuron coupled to it, and a presumed primary motoneuron show that: (1) the interneurons produce monosynaptic, CI−‐dependent IPSPs in contralateral motoneurons, (2) the interneurons are responsible for the short latency, crossed spinal inhibition in the M‐cell network, and (3) more than one interneuron terminates on each postsynaptic cell. Reconstructions of interneurons from wholemounts show that they form a fairly homogeneous morphological class of cells. Each one is unipolar, with an axon that crosses the cord and then usually bifurcates into a short, thin ascending branch and a thicker, longer descending one. Neighboring interneurons have overlapping terminal arbors consistent with the physiological data showing convergence of interneurons onto the same postsynaptic cell. The interneurons showed little relationship with body segments as denned by ventral roots. Their axons usually straddled segmental boundaries, with terminals typically occupying parts of two adjacent segments. Thus the functional unit of these cells is probably not a segment or a complete group of segments, but instead includes only parts of two adjacent segments. The presence of interneurons like these suggests that the overt peripheral segmentation of trunk musculature is not necessarily reflected in the organization of neurons that control those segments. A consideration of some functional characteristics of the activation of overlapping, serially repeated arrays of interneurons by descending pathways leads to the conclusion that the high conduction velocity of the M‐axon, and the large size and short longitudinal extent of the axons of the inhibitory interneurons promote a strong, brief inhibition that is appropriate for the production of an escape turn that has a rapid bend

ISSN:0092-7317    

DOI:10.1002/cne.902990303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractOne hypothesis for the coding of olfactory quality is that regions of the olfactory epithelium are differentially sensitive to particular odor qualities and that this regional sensitivity is conveyed to the olfactory bulb in a topographic manner by the olfactory nerve. A corollary to this hypothesis is that there is a sufficiently orderly connection between the epithelium and the olfactory bulb to convey this topographical coding. Thus we examined topography in the projection from epithelium to bulb in the frog, which has been the subject of numerous electrophysiological studies but has not yet been examined using modern neuroanatomical techniques.The tracer WGA‐HRP was applied to the ventral or to the dorsal olfactory epithelium, or both. Anterograde transport of label to the olfactory bulb was seen after as few as 2 days; label was still present in the bulb as long as 21 days postinjection. In cases where WGA‐HRP was applied to the entire epithelium, there was dense anterograde labelling of the ipsilateral olfactory bulb. In addition, a small medial portion of the contralateral bulb was labelled.Injections limited to either the ventral or dorsal epithelium produced patterns of anterograde labelling in the glomerular layer of the olfactory bulb, which varied with the size and location of the injection. With very large injections in either the dorsal or ventral epithelium, label appeared to be evenly distributed in the glomerular layer. With smaller injections in the ventral epithelium, there was heavier labelling in the lateral than in the medial portions of the glomerular layer, although light labelling was found in all regions of the glomerular layer. In contrast, injection sites restricted to the dorsal epithelium produced more anterograde labelling in the medial than lateral portions of the glomerular layer. These patterns extended throughout the dorsal‐ventral extent of the bulb.Within the limits of the anterograde tracing technique used, we were unable to detect any systematic relationship between the pattern of labelling in the glomerular layer and the medial‐lateral or rostral‐caudal location of the injection site in either the ventral or dorsal epithelium.We conclude that in the frog, as in other amphibia, there is only a limited degree of topographic order between the epithelium and the olfac

ISSN:0092-7317    

DOI:10.1002/cne.902990304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractMorphological changes in individual corticorubral fibers and the pattern of crossed and uncrossed corticorubral projections were studied during the postnatal development of cats in order to understand cellular mechanisms for restriction of corticorubral projections with development. The anterograde tracerPhaseolus vulgarisleucoagglutinin (PHA‐L) was injected into restricted areas of the pericruciate cortex in kittens and PHA‐L‐labeled axons in the red nucleus were examined at postnatal days (PND) 7–73.In accordance with our previous study (Murakami and Higashi, Brain Res. 1988;447:98–108), a crossed corticorubral projection was observed in addition to the uncrossed one in every experimental animal. During the early period of development (PND 7–8), swellings of irregular shape were observed along the entire course of the axons and they were often interconnected with extremely fine axonal segments. These axons bifurcated only infrequently and often ended as growth cones. These features were common to both uncrossed and crossed corticorubral axons. At later stages of development (PND 28 or later), the total number of swellings decreased and axonal swellings with smooth contours became dominant.A quantitative examination of axonal branches indicated that axons on the ipsilateral side branch occurred more frequently at later stages of development. However, there was no substantial change in branching frequency for the crossed corticorubral fibers during development. In parallel with morphological changes in individual axons, the crossed projection that was initially relatively abundant was reduced during development, Since a PHA‐L injection can be confined to a small region of cortex, topographic projections can easily be detected. At PND 7–8 there was no well‐defined topographic order in the ipsilateral corticorubral projection. Adult‐like topography was first discernible at PND 13.These observations suggest that the unilateral uncrossed corticorubral projection in the adult cat is achieved at least in part by the formation of axonal arbors in the uncrossed projection. This was accompanied by the failure of crossed fibers to form complex arbors. It is possible that a similar mechanism also operates in the formation

ISSN:0092-7317    

DOI:10.1002/cne.902990305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractDARPP‐32, a dopamine (DA) and cAMP‐regulated phosphoprotein, is associated with dopaminoceptive neurons bearing D‐1 receptors in the basal ganglia. The present study addressed the distribution of DARPP‐32 in the primate cerebral cortex and its putative association with D‐1 receptor laden cells in this structure. DARPP‐32‐like immunoreactive (LIR) neurons were examined in the cerebral cortex of 3‐day‐old (P3), 6‐week‐old (P42), and adult rhesus monkeys. In the younger cases, a large number of DARPP‐32 positive neurons, with the morphological characteristics of pyramidal cells, were observed throughout the cortex, in layers V–VI, and to a lesser extent in layer II and uppermost layer III. In the parietal, insular, temporal, and occipital cortices, DARPP‐32 positive neurons were arranged in a monolayer in layer Va. They were often clustered in small groups with a bundling of their dendrites. In the primary motor cortex, Betz cells were among the labeled population. In the association and somatosensory areas, the basal dendrites of DARPP‐32 positive neurons and the prominent tufting of their apical dendrites in layer I contributed to an essential bilaminar pattern resembling the distribution reported for DA afferents and D‐1 receptors in these areas. The prominence and widespread distribution of DARPP‐32 positive neurons in layer V may be a specialization of primate cortex since such cells are found only in restricted locations in rodents. The literature on the connections of the cerebral cortex suggests that a large number of the DARPP‐32 positive neurons in layer VI and perhaps even in layer Va may be corticothalamic neurons. An important developmental observation was the presence of DARPP‐32‐LIR neurons in the white matter. They were prominent in the neonates but could not be seen in the adult. Their location as well as their type and shape were reminiscent of interstitial neurons. In the adult monkeys, the distribution of DARPP‐32‐LIR neurons was more circumscribed: they were numerous in the ventral temporal gyrus and in areas related to the limbic system: caudal orbitofrontal cortex, insula, temporal pole, entorhinal, and anterior cingulate cortex. Weak labeling was detected in layer Va of the superior temporal and parietal cortex, in some prefrontal areas (10,13, and medial 9), and in the premotor and supplementary motor cortex; in adults, unlike neonates, few DARPP‐32‐LIR neurons were present in the dorsolateral prefrontal cortex, the primary motor or the primary visual or prestriate cortices. These findings demonstrate important developmental changes between birth and adulthood in the expression of DARPP‐32 and point to a possible role for this molecule and/or D‐1 receptors during p

ISSN:0092-7317    

DOI:10.1002/cne.902990306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractPlasticity of dorsal root (DR) and descending serotoninergic (5‐HT) projections following dorsal rhizotomy fromL2 to S1 sparing L5 was studied by means of an intra‐animal comparison in the adult rat spinal cord. Projections of the chronically and acutely spared root were compared by cholera‐toxin conjugated horseradish peroxidase (CT‐HRP) injected into the sciatic nerves as the transganglionic tracer. Projections in unoperated controls, operated controls (acute bilateral spared root), and in experimental animals (chronic spared root on one side and acute spared root on the other) were mapped and the density was measured with an image analysis system. Labeled DRG cells and motor neurons were counted to determine if there were differences in the delivery of the label between the two sides. Measurements of the area of the dorsal horn and, separately, of the superficial laminae were made to control for shrinkage.DR projections were symmetrical in operated and unoperated controls, but a significant increase in DR projection density was found from L6 to L3 in the dorsal horn and Clarke's nucleus at L1 on the chronic spared root side in animals in which an equal number of DRG cells was labeled on the two sides. Density of 5‐HT immunoreactivity was symmetrical in controls. Ipsilateral to chronic spared root rhizotomy, the area fraction occupied by 5‐HT projections increased in Clarke's nucleus and in the superficial dorsal horn of all partially deafferented segments except L5, the spared root segment.Partial deafferentation of the adult rat lumbosacral spinal cord may therefore elicit sprouting from the spared dorsal root and, outside of the dorsal root projection zone, sprouting from the spared descending 5‐HT system. Plasticity of dorsal root projections and of 5‐HT projections occur in different regions; in regions of the increased spared root projection, no increase is seen in 5‐HT projections, suggesting that sprouting in the adult rat spinal cord is regulated, perhaps by competitive or hierar

ISSN:0092-7317    

DOI:10.1002/cne.902990307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn teleost retinas, the somata of same‐type cone horizontal cells are electrically coupled via extensive gap junctions, as are the axon terminals of same‐type cells. This coupling persists throughout the animal's life and is modulated by dopamine and conditions of light‐ vs. dark‐adaptation. Gap junction particle density in goldfish horizontal cell somata has also been shown to change under these conditions, indicating that these junctions are dynamic. We have used electron microscopy to examine gap junctions in bass horizontal cells with a fixation method that facilitates detection of gap junctions. Annular gap junction profiles were observed in the somatic cytoplasm of all cone horizontal cell types in both light‐ and dark‐adapted animals. Serial sections showed that most profiles represented gap junction vesicles free within the cytoplasm; the remainder represented vesicles still attached to extensive plasma membrane gap junctions by a thin cytoplasmic neck, suggestive of an intermediate stage in endocytosis. Observations of gap junction vesicles containing fragments of gap junctional membrane and/or fused with lysosomal bodies further supported this hypothesis. Because gap junctions persist between the horizontal cells, we propose that gap junction endocytosis and lysosomal degradation are balanced by addition of new junctions. While endocytosis has been widely demonstrated to serve in programmedremovalof gap junctions (without subsequent replacement), from both nonneuronal cells and developing neurons, this study indicates that it can also function in the renewal of electrical synapses in the adult teleost retina, where gap junction elimination is

ISSN:0092-7317    

DOI:10.1002/cne.902990308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractElectrophysiological experiments have predicted a direct synaptic input from glycinergic interplexiform cells (IPCs) to GABAergic horizontal cells in the Xenopus retina. However, previous ultrastructural studies failed to demonstrate this input. Here, we used three immunocytochemical approaches to investigate this issue. First, double‐label postembedding immunocytochemistry with GABA‐ and glycine‐like immunoreactivity (GABA‐LI and glycine‐LI) was used to study possible interactions of the glycinergic IPC with GABAergic horizontal cells. Processes postsynaptic to glycine‐LI IPC terminals in the outer plexiform layer (OPL) fell into two groups, small microtubule‐filled processes and larger electron‐lucent processes with sparse microtubules and occasional mitochondria. In no case did we find glycine‐LI synapses onto GABA‐LI cells or processes. Second, pre‐embedding immunocytochemistry was used to label GABA‐LI cells and processes in the OPL. GABA‐LI was sparse in horizontal cell axons and more intense in horizontal cell somas and in small processes. In agreement with our first set of experiments, GABA‐LI profiles did not receive input from conventional synapses. Third, we localized glycine‐receptor‐like immunoreactivity (GlyR‐LI) to several types of apparent synapses in the OPL. As expected, it was found at IPC synapses. Unexpectedly, GlyR‐LI was also subsynaptic at photoreceptor synapses onto second order neurons, both at ribbon and basal junction type synapses. At least some of the GlyR‐LI photoreceptor synapses were from cones. Also, GlyR‐LI was apposed to photoreceptors and to unidentified small diameter processes, where no other indication of synaptic input was evident. Because glycine‐LI is not found in photoreceptors, we suggest that glycine receptors at photoreceptor synapses are stimulated by glycine that diffuses from other sites, possibly from IPCs. This interpretation is consistent with available physiological stud

ISSN:0092-7317    

DOI:10.1002/cne.902990309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902990301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY