摘要:

AbstractA population of some 35 intersegmental interneurones with somata in the metathoracic ganglion has been characterized by intracellular recording and staining. These interneurones integrate signals from extero‐ and proprioceptors on a hind leg. The somata are clustered in an anterior and lateral region of the dorsal cortex, and the axons project to more anterior ganglia in either the ipsilateral or contralateral connectives.Some of these interneurones are excited by afferents from a proprioceptor at the femorotibial joint, the femoral chordotonal organ. An afferent spike evokes a chemically mediated EPSP in an interneurone with a latency and consistency that suggest that the connection is direct. An individual interneurone codes particular features of the movement about the femorotibial joint, responding to flexion, extension, or both directions of movement with either phasic or tonic responses. These interneurones have an extensive field of fine branches ipsilateral to the hind leg from which they receive input. These branches are in lateral and intermediate regions of neuropil to which the afferents of the chordotonal organ also project. Axonal branches, from either an ipsilateral and contralateral axon, are sparse and varicose and occur in dorsal neuropil.Other interneurones are excited by afferents from exteroceptive hairs (trichoid sensilla). An individual interneurone is excited by a particular array of hairs on specific regions of a hind leg. The connections between the afferents and the interneurones appear direct. These interneurones have a dense and compact array of fine branches ipsilateral to the hind leg from which they receive input. These branches are in the most ventral region of neuropil, to which the hair afferents also project. Branches from the ipsilateral axons are sparse and varicose and occur in more dorsal neuropil.The interneurones can thus provide the more anterior ganglia with precise information about the movement of a joint in a hind leg and of the location of an exteroceptive stimulus. This information would be of importance in ensuring the correct co‐ordination of the legs during walk

ISSN:0092-7317    

DOI:10.1002/cne.902750102

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe corticotropin‐releasing hormone (CRH) neurosecretory system in normal rats consists of two major subpopulations of parvicellular neurons in the hypothalamic paraventricular nucleus distinguished by the presence or absence of coexistent vasopressin precursor (pro‐AVP)‐derived peptides. These neurons project to the external zone of the median eminence, where the two subtypes of axons (CRH+/AVP+ and CRH+/AVP‐) were previously found to be approximately equal in number. The present study was undertaken (1) to determine whether the relative numbers of pro‐AVP expressing and pro‐AVP deficient perikarya in the paraventricular nucleus corresponded to what we previously found for the axons in the median eminence, (2) to map the two cell types throughout the entire paraventricular nucleus to determine whether significant differences existed in their distributions, and (3) to ascertain whether or not the pro‐AVP deficient subpopulation expressed pro‐AVP after adrenalectomy. Postembedding electron microscopic immunocytochemistry on serial ultrathin sections was used to identify the peptide phenotypes of perikarya in the paraventricular nucleus in normal rats and 7 days after adrenalectomy with and without colchicine treatment. The peptide phenotypes of neuronal perikarya in the paraventricular nucleus were identified by using antibodies to CRH, AVP, neurophysin (NP), the C‐terminal glycopeptide of pro‐AVP (GP), and oxytocin‐associated neurophysin (NPOT). Groups of three serial coronal ultrathin sections were analyzed at 200‐μm intervals throughout the entire rostrocaudal extent of the paraventricular nucleus. The sections in each group were stained for CRH, a pro‐AVP‐derived peptide (AVP, NP or GP), and NPOT, respectively. Parvicellular CRH neurons were defined as CRH‐positive cells, approximately 10 μm in diameter, that did not contain detectable NPOT. Pro‐AVP expressing cells were defined as staining positively for AVP, GP, or NP and negatively for NPOT. Approximately equal numbers of pro‐AVP expressing (“NPAVP+”) and pro‐AVP deficient (“NPAVP‐”) parvicellular CRH neurons were found within the paraventricular nucleus of colchicine‐treated normal rats, and the two subtypes were distributed differently within the paraventricular nucleus. Although the pro‐AVP expressing CRH cells stained intensely for NP and GP, staining for AVP was quite variable and difficult to quantify in colchicine‐treated normal animals. The CRH+/NPAVP+ neurons were highly concentrated in the dorsal third of the medial parvicellular subdivision of the paraventricular nucleus, in a region roughly midway between the rostral and caudal ends of the paraventricular nucleus, while the CRH+/NPAVP‐ neurons were more spread out in the medial parvicellular subdivision in both the dorsoventral and the rostrocaudal axes. Adrenalectomy had no effect on the total number of CRH cells or their distribution in colchicine‐treated rats. However, more than 90% of the parvicellular, NPOTnegative CRH neurons in the paraventricular nucleus stained intensely for AVP, NP, or GP after adrenalectomy and colchicine treatment. The different distributions of the two subpopulations within the paraventricular nucleus in colchicine‐treated normal rats suggest possible differences in the nature of their afferent inputs, and the changes induced by adrenalectomy indicate that normal circulating levels of glucocorticoids are sufficient to inhibit expression of pro‐AVP in one subpopulation but not the other. However, both subpopulations are regulated by glucocorticoids, as evidenced by the increased staining for AVP in both subpopulations after adrenalectomy. The present results are consistent with our hypothesis of functionally distinct subpopulations of CRH neurons that could modulate the ratio o

ISSN:0092-7317    

DOI:10.1002/cne.902750103

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

年代:1988

数据来源: WILEY

摘要:

AbstractAxon‐bearing horizontal cells of theXenopusretina were studied by intracellular injection of HRP following physiological characterization. The profile of the cell viewed in whole mount consisted of a round or oval perikaryon about 50 μm in diameter and an axon about 1 mm long which lacked a prominent terminal expansion. The axonal diameter was 0.5‐1.0 μm in its proximal third but 2‐4 μm in its distal portion. Along its course the axon emitted 25‐40 branchlets each 0.2 μm in diameter, up to 10 μm long and terminating in a cluster of two to six synaptic knobs. Electron microscopic examination revealed that both perikaryal dendrites and axon branchlets ended in both rod and cone synaptic bases; cone contacts outnumbered rod contacts by two‐ to threefold. We were unable to document synapses of presumed interplexiform cells onto identified horizontal cells. Horizontal cell axons are joined in their distal portions by numerous, small (0.2 μm long) gap junctions. Other gap junctions were noted between horizontal cell processes within the synaptic endings of photoreceptors. An hypothesis is advanced whereby the cluster of axon branchlet synaptic knobs permits dynamic interaction of rod and cone synaptic inputs to the

ISSN:0092-7317    

DOI:10.1002/cne.902750104

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe present study provides a comprehensive light and electron microscopic analysis of the anatomical organization of the rat mamillary body. The cytoarchitecture and morphology of mamillary neurons were investigated with the aid of Nissl‐stained and Golgi‐impregnated sections cut in transverse, horizontal, and sagittal planes. The ultrastructural features of the mamillary nuclei were correlated with observations made on Golgi material. The mamillary body is comprised of a lateral and a medial nucleus, the latter being subdivided into five major subnuclei: pars lateralis, pars basalis, pars medialis, pars medianus, and pars posterior. The perikarya are medium‐sized or small with the proportions of each differing among subnuclei. The largest perikarya are found in the lateral mamillary nucleus (cell area 257.0 μm2) and have 2‐5 radially oriented aspiny dendrites that are often beaded. Small cells predominate in the pars lateralis (cell area 116.3 μm2) and pars basalis (cell area 118.3 μm2), whereas the pars medialis (cell area 196.7 μm2), pars medianus (cell area 136.5 μm2), and pars posterior (cell area 154.6 μm2) contain mainly medium‐sized cells. The dendrites of most cells in the medial nucleus are radially oriented and exhibit a variety of spines including numerous short stubby spines, spines with thin necks that end in spherical swellings, and long thin spines. Neuronal somata are often closely apposed with no intervening glial processes and contain eccentrically located nuclei with one or more invaginations of the nuclear envelope.Two main classes of axon terminals were identified in the mamillary body. One type contains round vesicles and forms asymmetric synaptic junctions (RA) with dendrites and dendritic spines. RA terminals rarely contact neuronal somata and proximal dendrites in the MB. The second type contains pleomorphic vesicles and forms mainly symmetric synaptic junctions (PS) with neuronal somata as well as dendrites and spinous processes. Dense‐cored vesicles were frequently seen in both types of terminals. Both types of terminals often synapse with two adjacent dendrites and are also found near or adjacent to each other on the same dendrite. A quantitative analysis indicated that the numbers of RA terminals in the medial nucleus almost equals the numbers of PS terminals, whereas the lateral mamillary nucleus contains considerably more PS (64%) than R

ISSN:0092-7317    

DOI:10.1002/cne.902750105

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

年代:1988

数据来源: WILEY

摘要:

AbstractThere is some controversy in the literature whether carbonic anhydrase occurs in astrocytes, as well as in oligodendrocytes and myelin, in the mammalian brain. In the present study this issue was addressed by double immunostaining for carbonic anhydrase and two astrocytic “markers” in the brains of normal mice and two dysmyelinating mutants, jimpy and shiverer. In the brains of young mice, carbonic anhydrase and glutamine synthetase were colocalized in astrocytes in the cortical gray matter. In gray matter of the adult mouse brain, it was possible to immunostain both carbonic anhydrase and glial fibrillary acidic protein (GFAP) in the same cells. However, in contrast to the findings in gray matter, in and near subcortical white matter carbonic anhydrase could be detected only in oligodendrocytes and myelinated fibers. In the brains of jimpy mice, virtually all the carbonic‐anhydrase‐positive cells were also GFAP positive, even in regions normally occupied by white matter. In the brains of young and adult shiverer mice, carbonic anhydrase was localized in astrocytes in the gray matter, but in and near the tracts normally occupied by white matter carbonic anhydrase could be detected only in oligodendrocytes and their abundant process. The findings confirmed the oligodendrocyte‐myelin unit to be the primary locus of carbonic anhydrase in the normal mouse brain and showed the astrocytes in gray matter normally to be a secondary locus of carbonic anhydrase. The immunostaining in the jimpy mouse brain suggested further that reactive astrocytes, in particular, might be rich in carbonic

ISSN:0092-7317    

DOI:10.1002/cne.902750106

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

年代:1988

数据来源: WILEY

摘要:

AbstractNeuroanatomical and ultrastructural studies of the paired lateral giant nerve fibers (LGFs) in posterior segments of the tubificid worm,Branchiura sowerbyi, demonstrate that the fibers are (1) segmental in origin (two cell bodies per segment), (2) joined longitudinally and transversely to form an intersegmental syncytial network, and (3) surrounded by a myelinlike sheath. The LGFs are unique among paired giant fiber systems because of their extreme asymmetry, the diameter of the left fiber being several times greater than that of the right. Electrophysiological studies demonstrate that the small, right fiber has a high input resistance and, during mechanosensory stimulation, functions as the locus for LGF spike initiation. The larger, left fiber contributes by enhancing the speed of LGF spike conduction along the animal. One physiological benefit of this asymmetric arrangement may be optimization of escape reflex sensitivity to mechanosensory inputs.

ISSN:0092-7317    

DOI:10.1002/cne.902750107

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

年代:1988

数据来源: WILEY

摘要:

AbstractA monoclonal antibody (Ab8) to choline acetyltransferase (ChAT) was used to locate structures showing ChAT‐like immunoreactivity (ChAT‐IR) in the brain of a teleost fish, the midshipman (Porichthys notatus). ChAT is the synthetic enzyme for acetylcholine found in neurons using that neurotransmitter; thus ChAT‐IR may be interpreted as indicating putative cholinergic activity. Robust staining is seen in all cranial nerve motor nuclei. In addition, the brainstem ofPorichthysis distinguished by two other expansive ChAT‐IR zones: a sonic motor nucleus, which innervates swimbladder “drum” muscles, and an octavolateralis efferent nucleus, which innervates acoustic, vestibular, and lateral line end organs. Scattered labeled cells are found in several cranial sensory nuclei–the vagal lobe, and the main and descending trigeminal nuclei. ChAT‐IR cells form restricted subpopulations in other noncranial nerve nuclei, including the granule cell layer of the cerebellum; superior, medial, and inferior divisions of the reticular formation; the stratum periventriculare of the midbrain's optic tectum; and the nucleus isthmi in the midbrain tegmentum. In the telencephalon, a dense population of ChAT‐IR cells is found in the ventral nucleus of area ventralis; terminals and fine fibers are found in the dorsal, medial, and central nuclei of area dorsalis. Together, the data represent the first complete report of ChAT‐IR cell bodies in the brain of any nonmammal with the monoclonal antibody Ab8, which has already been extensively used on a variety of vertebrate brains. The results are thus discussed from a comparative viewpoint, considering reports of ChAT

ISSN:0092-7317    

DOI:10.1002/cne.902750108

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

年代:1988

数据来源: WILEY

摘要:

AbstractUsing the indirect antibody peroxidase‐antiperoxidase method of Sternberger, we localized substance P (SP), somatostatin (SOM), enkephalin (ENK), and serotonin (5HT, 5‐hydroxytryptamine) in the spinal cord ofRana pipiens. This is the first study to demonstrate all four substances in adjacent sections of frog spinal cord. The distribution patterns of ENK, SP, SOM, and 5HT in our study differ from that described for laminae I and II in amniotes. A high density of ENK, SP, and SOM fibers is present in a band ventral to the dorsal terminal field of cutaneous primary afferent fibers and slightly overlapping the ventral terminal field of muscle primary afferent fibers. However, a high density of 5HT fibers is present in the dorsal terminal fi

ISSN:0092-7317    

DOI:10.1002/cne.902750109

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe topographical and ultrastructural organization of the habenular projection to the interpeduncular nucleus (IPN) of the rat was examined employing the anterogradely transported tracer wheat germ agglutininhorseradish peroxidase (WGA‐HRP) and the chromogen tetramethylbenzidine (TMB). Unilateral placements of WGA‐HRP in the habenular complex resulted in heavy terminal labelling in the rostral, central, and intermediate subnuclei bilaterally, and in the lateral subnuclei ipsilaterally. The apical subnucleus possessed only a sparse amount of label. Placements confined to the medial habenula (mH) produced similar results to those observed when the entire habenula was filled, suggesting that the afferent contribution made by the lateral habenula (lH) to the IPN is small.Unilateral placements of WGA‐HRP in the dorsal portion of the mH resulted in heavy, predominantly ipsilateral labelling in the lateral subnucleus and the dorsal cap of the rostral subnucleus. In the lateral subnucleus labelled habenular terminals consistently contacted single dendritic processes shared by one or more other boutons, possibly of nonhabenular origin. Labelled habenular terminals in the rostral subnucleus normally contacted one or two dendrites. Labelled terminals in both subnuclei possessed clear, spherical vesicles and a variable number of dense‐core vesicles. Unilateral placements of WGA‐HRP in the ventral portion of the mH resulted in heavy labelling in the rostral half of the rostral subnucleus with a slight ipsilateral predominance, and in the central and intermediate subnuclei bilaterally. Terminal labelling was observed in crest and S synapses in the intermediate and central subnuclei respectively. Crest synapses, which consist of two parallel habenular terminals contacting an attenuated dendritic process, normally possessed label in only one of the two boutons. In the central subnucleus labelled horizontal axons formed several en passant S synapses with dendritic processes of small and medium diameter. These synaptic specializations of habenular axons contained numerous clear, spherical vesicles.This study demonstrates that a major topographically organized projection to the IPN originates from two distinct subpopulations of habenular neurons which comprise a dorsal sector and a ventral sector of the mH. Ultrastructural examination demonstrated that axons originating from neurons in the ventral and dorsal mH form characteristic contacts in the various IPN

ISSN:0092-7317    

DOI:10.1002/cne.902750110

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe abdominal prolegs are the principal locomotory appendages of the larval tobacco hornworm,Manduca sexta. The prolegs bear numerous mechanosensory bristle sensilla, each innervated by an afferent neuron that arborizes within the central nervous system (CNS). Based on their positions on the proleg, we have divided the sensilla into planta hairs (PHs), lateral hairs (LHs), and medial hairs (MHs). Previously, we found that PH afferents produce monosynaptic excitatory postsynaptic potentials (EPSPs) in proleg retractor muscle motoneurons, the size of which depends on the position of the hair in the PH array. In this paper we examined the central arbors of the proleg afferents to determine whether there was an anatomical correlate to the pattern of synaptic strengths. We found that the afferent arbors are arranged somatotopically within the CNS in a pattern similar to that for bristle afferents elsewhere on the abdomen; i.e., the anterior‐posterior and medial‐lateral position of a hair on the proleg was reflected in the location of the afferent arbor along the corresponding axes within sensory neuropil. All afferents terminated within a similar ventral region of neuropil. The arbors of PH, MH, and to a lesser extent, LH afferents, were enlarged as compared to afferents innervating hairs elsewhere on the abdomen. This feature, combined with the dense innervation of the proleg, causes the proleg region to be relatively overrepresented in sensory neuropil. We also examined the afferents innervating a pair of ventral midline hairs (VMHs) present in each abdominal segment, which, unlike the other afferents, showed segment‐specific central arbors. We conclude that the somatotopic mapping of afferent arbors may contribute to the specificity of synaptic connections in this s

ISSN:0092-7317    

DOI:10.1002/cne.902750111

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

年代:1988

数据来源: WILEY