Retinal organization in the bcl‐2‐overexpressing transgenic mouseStrettoi, Enrica; Volpini, Maila
doi: 10.1002/cne.10177pmid: 11920715
Naturally occurring cell death is believed to play a major role during the development of the nervous system in the establishment of neuronal architecture. Here we study the effects of cell death inhibition by using a transgenic mouse in which the powerful antiapototic gene bcl‐2 is expressed in neurons. The retina of this mouse reveals that the general neuronal plan has been maintained. However, bcl‐2 overexpression leads to altered frequencies of the major cell types in the retina. Thus, it is possible to estimate cell‐type‐specific rates of apoptosis by observing the increases in numbers of cells in the bcl‐2‐overexpressing transgenic mouse. J. Comp. Neurol. 446:1–10, 2002. © 2002 Wiley‐Liss, Inc.
Descending supraspinal pathways in amphibians: III. Development of descending projections to the spinal cord in Xenopus laevis with emphasis on the catecholaminergic inputsSánchez‐Camacho, Cristina; Martín, Oscar; Ten Donkelaar, Hans J.; González, Agustín
doi: 10.1002/cne.10170pmid: 11920716
In developmental stages of the clawed toad, Xenopus laevis, we describe the ontogeny of descending supraspinal connections, catecholaminergic projections in particular, by means of retrograde tracing techniques with dextran amines. Already at embryonic stages (stage 40), spinal projections from the reticular formation, raphe nuclei, Mauthner neurons, vestibular nuclei, the locus coeruleus, the interstitial nucleus of the medial longitudinal fasciculus, the posterior tubercle, and the periventricular nucleus of the zona incerta are well developed. At the beginning of the premetamorphic period (stage 46), spinal projections arise from the suprachiasmatic nucleus, the torus semicircularis, the pretectal region, and the ventral telencephalon. After stage 48, tectospinal and cerebellospinal projections develop, with spinal projections from the preoptic area following at stage 51. Rubrospinal projections are present at stage 50. During the prometamorphic period, spinal projections arise in the nucleus of the solitary tract, the lateral line nucleus, and the mesencephalic trigeminal nucleus. With in vitro double‐labeling methods, based on retrograde tracing of dextran amines in combination with tyrosine hydroxylase (TH) immunohistochemistry, we show that at stage 40/41, catecholaminergic (CA) neurons in the posterior tubercle are the first to project to the spinal cord. Subsequently, at stage 43, new projections arise in the periventricular nucleus of the zona incerta and the locus coeruleus. The last CA projection to the spinal cord originates from neurons in the nucleus of the solitary tract at the beginning of prometamorphosis (stage 53). Our data show a temporal, rostrocaudal sequence in the development of the CA cell groups projecting to the spinal cord. Moreover, the early appearance of CA fibers, preterminals and terminal‐like structures in dorsal, intermediate, and ventral zones of the embryonic spinal cord, suggests an important role for catecholamines during development in nociception, autonomic functions, and motor control at the spinal level. J. Comp. Neurol. 446:11–24, 2002. © 2002 Wiley‐Liss, Inc.
Central organization of the electrosensory system in the paddlefish (Polyodon spathula)Hofmann, Michael H.; Wojtenek, Winfried; Wilkens, Lon A.
doi: 10.1002/cne.10194pmid: 11920717
The central connections of the electrosensory system were studied in the paddlefish Polyodon spathula by injecting biotinylated dextran amines into the dorsal octavolateral nucleus (DON), the cerebellum, and the mesencephalic tectum. The sole target of primary electrosensory fibers is the ipsilateral dorsal octavolateral nucleus. The principal neurons ascending from this nucleus project to the torus semicircularis, the lateral mesencephalic nucleus, and the mesencephalic tectum. The mesencephalic tectum projects back to the nucleus preeminentialis, which, in turn, projects to the cerebellar auricles and to the DON. The auricles are the main source of parallel fibers in the cerebellar crest ventral to the DON. The DON also receives input from the contralateral DON. These descending feedback loops are very similar to those of other electrosensory fishes. However, the paddlefish is unique in having three mesencephalic targets of electrosensory information. It is the only bony fish known to have extensive projections directly to the mesencephalic tectum and to a lateral mesencephalic nucleus in addition to the torus semicircularis. J. Comp. Neurol. 446:25–36, 2002. © 2002 Wiley‐Liss, Inc.
Calcyon in the rat brain: Cloning of cDNA and expression of mRNAZelenin, Sergey; Aperia, Anita; Diaz Heijtz, Rochellys
doi: 10.1002/cne.10198pmid: 11920718
Calcyon is a 24 kD protein recently cloned from a human brain cDNA library and shown to interact with the dopamine receptor 1 (D1R) of D1‐like receptors. This interaction shifts the effector coupling of D1R to stimulate a calcium signaling pathway, without influencing the D1R‐adenylyl‐cAMP pathway. To obtain more knowledge about the potential role of calcyon in the brain, we cloned rat calcyon cDNA and studied its distribution in the brain. Northern blot analysis and RT‐PCR revealed that rat calcyon mRNA was expressed only in the brain. With the use of the in situ hybridization technique, we studied rat calcyon mRNA distribution in the brain and related it to the distribution of D1R and dopamine receptor 5 (D5R) mRNAs. Prominent calcyon mRNA signals were found in several brain regions, including hippocampus, hypothalamus, cerebellum, and medial prefrontal cortex. Less abundant calcyon mRNA expression was observed in the dorsal striatum region, where D1R mRNA is highly expressed and where D1R/cAMP‐DARPP‐32 signaling pathway is of great functional importance. The strongest expression of D5R mRNA was found in the hippocampus and cerebellum, where D1R mRNA expression was relatively low. In conclusion, rat calcyon appears to be a brain specific protein. There is a certain overlap between calcyon mRNA distribution and that of the D1R and D5 mRNAs, indicating that calcyon might be associated not only with D1R but also with D5R. J. Comp. Neurol. 446:37–45, 2002. © 2002 Wiley‐Liss, Inc.
Distribution and morphology of transgenic mouse oligodendroglial‐lineage cells following transplantation into normal and myelin‐deficient rat CNSSchiff, Rolf; Rosenbluth, Jack; Dou, Wen‐Kai; Liang, Wei‐Lan; Moon, David
doi: 10.1002/cne.10192pmid: 11920719
Glial cells from neonatal MβP5 transgenic mice, which express bacterial β‐galactosidase (lacZ) under control of the myelin basic protein (MBP) promoter (Gow et al, 1992), were transplanted into the spinal cord or cerebral hemisphere of immunosuppressed normal and myelin‐deficient (md) rats in order to assess the ability of the donor cells to survive, migrate, and differentiate within normal compared with myelin‐deficient central nervous system (CNS). LacZ+ cells were detected as early as 6–7 days after transplantation into the low thoracic cord and by 10 days had spread rostrally to the brainstem and caudally to the sacral spinal cord. Initially, compact lacZ+ cells, lacking processes, were found associated with small blood vessels and with the glia limitans. Cells of this type persisted throughout the experiment. Later, lacZ+ cells with processes were seen along fiber tracts in the dorsal columns and, after intracerebral injection, subjacent to ventricular ependyma, as well as scattered in cerebral white and gray parenchyma. The extent of spread was comparable in md and normal rats, but in the md group, the success rate was higher, and more cells differentiated into process‐bearing oligodendrocytes. Acceptance of xenografts in immunosuppressed recipients equaled that of allografts. The overall spread of grafted cells exceeded that of injected charcoal, indicating active migration. In contrast to earlier studies that identified oligodendrocytes based on morphology alone, this study has allowed us to identify and track oligodendrocytes based on myelin gene expression. We show some oligodendrocytes whose morphology is consistent with classical morphological descriptions, some that resemble astrocytes, and a class of compact perivascular oligodendrocyte‐lineage cells that we suggest are migratory. J. Comp. Neurol. 446:46–57, 2002. © 2002 Wiley‐Liss, Inc.
Functional aspects of dopamine metabolism in the putative prefrontal cortex analogue and striatum of pigeons (Columba livia)Bast, Tobias; Diekamp, Bettina; Thiel, Christiane; Schwarting, Rainer K.W.; Güntürkün, Onur
doi: 10.1002/cne.10187pmid: 11920720
Dopamine (DA) in mammalian associative structures, such as the prefrontal cortex (PFC), plays a prominent role in learning and memory processes, and its homeostasis differs from that of DA in the striatum, a sensorimotor region. The neostriatum caudolaterale (NCL) of birds resembles the mammalian PFC according to connectional, electrophysiological, and behavioral data. In the present study, DA regulation in the associative NCL and the striatal lobus parolfactorius (LPO) of pigeons was compared to uncover possible differences corresponding to those between mammalian PFC and striatum. Extracellular levels of DA and its metabolites (homovanillic acid [HVA], dihydroxyphenylacetic acid [DOPAC]) and the serotonin metabolite 5‐hydroxyindoleacetic acid (5‐HIAA) were investigated by in vivo microdialysis of urethane‐anesthetized pigeons under basal conditions and after systemic administration of D‐amphetamine. DA was reliably determined only in LPO dialysates, and DA metabolite levels were significantly higher in LPO than in NCL. The HVA/DOPAC ratio, indicating extracellular lifetime of DA, was more than twice as high in NCL than in LPO dialysates. After amphetamine, DA increased in LPO while still being undetectable in NCL, and DA metabolites decreased in both regions. 5‐HIAA slightly decreased in NCL dialysates. Amphetamine effects were delayed in NCL compared with the striatum. In conclusion, effects of amphetamine on the pigeon's ascending monoamine systems resemble those found in mammals, suggesting similar regulatory properties. The neurochemical differences between NCL and LPO parallel those between associative regions, such as PFC and dorsal striatum in mammals. They may reflect weaker regulation of extracellular DA, favoring DAergic volume transmission, in associative than striatal forebrain regions. J. Comp. Neurol. 446:58–67, 2002. © 2002 Wiley‐Liss, Inc.
Sublaminar organization of the mouse olfactory bulb nerve layerAu, Winnie W.; Treloar, Helen B.; Greer, Charles A.
doi: 10.1002/cne.10182pmid: 11920721
Olfactory sensory neuron (OSN) axons coalesce to form the olfactory nerve (ON) and then grow from the olfactory epithelium to the olfactory bulb (OB), enter the olfactory nerve layer (ONL), reorganize extensively, and innervate specific glomeruli. Within the ON and ONL a population of glial cells, the olfactory ensheathing cells (OECs), surround OSN axon fascicles. To better understand the relationship between OECs and axon fascicles in the ONL of the adult mouse, we used confocal microscopy and antibodies to the low affinity nerve growth factor receptor p75 (p75), glial fibrillary acidic protein (GFAP), neuropeptide Y (NPY), and S‐100 to identify glia. Antibodies to olfactory marker protein (OMP) and neuronal cell adhesion molecule (NCAM) were used to identify OSN axons. Electron microscopy characterized the ONL ultrastructure. We found that glial processes were not uniformly distributed in the ONL of the mouse. The p75+ OEC processes were restricted to the ON and the outer ONL sublamina, and oriented parallel to the plane of the OB layers. In the inner ONL NPY+ OEC‐like processes were seen. GFAP+ processes were restricted to the inner ONL sublamina, the ONL/GL boundary, and the GL, where they delineated loosely aggregated axon fascicles that entered the glomeruli obliquely. S‐100+ processes and somata were distributed throughout the ONL; the outer and inner ONL were equivalent in their S‐100 staining. Ultrastructural studies showed that, although OECs could be identified in both the outer and inner ONL, in the latter, their relationship to bundles of OEC axons appeared less orderly than seen in the outer ONL. Our data demonstrate a differential organization of the ONL that could subserve distinct functions; axon extension may occur predominately in the outermost ONL, whereas glomerular targeting occurs in the inner sublamina of the ONL. J. Comp. Neurol. 446:68–80, 2002. © 2002 Wiley‐Liss, Inc.
Axonal projections of pulmonary slowly adapting receptor relay neurons in the ratEzure, Kazuhisa; Tanaka, Ikuko; Saito, Yoshiaki; Otake, Kazuyoshi
doi: 10.1002/cne.10185pmid: 11920722
We elucidated efferent projections of second‐order relay neurons (P‐cells) activated by afferents originating from slowly adapting pulmonary receptors (SARs) to determine the central pathway of the SAR‐evoked reflexes. Special attention was paid to visualizing the P‐cell projections within the nucleus tractus solitarii (NTS), which may correspond to the inhibitory pathway from P‐cells to second‐order relay neurons (RAR‐cells) of rapidly adapting pulmonary receptors. P‐cells were recorded from the NTS in Nembutal‐anesthetized, paralyzed, and artificially ventilated rats. First, we used electrophysiological methods of antidromic mapping and showed that the majority of the P‐cells examined projected their axons to the caudal NTS and to the dorsolateral pons corresponding to the parabrachial complex. Second, a mixture of HRP and Neurobiotin was injected intracellularly or juxtramembranously into P‐cells. (1) Stained P‐cells (n = 7) were located laterally to the solitary tract and had dendrites extending characteristically along the lateral border of the solitary tract. (2) All P‐cells had stem axons projecting to the ipsilateral medulla. Of these, the axons from five P‐cells projected to the nucleus ambiguus and its vicinity with distributing boutons. Some of these axons further ascended in the ventrolateral medulla, and distributed boutons in the areas ventral or ventrolateral to the nucleus ambiguus. (3) All the P‐cells had axonal branches with boutons in the NTS area. In particular, axons from three P‐cells projected bilaterally to the medial NTS caudal to the obex, i.e., to the area of RAR‐cells. These results show anatomic substrates for the connections implicated in the P‐cell inhibition of RAR‐cells as well as the SAR‐induced respiratory reflexes. J. Comp. Neurol. 446:81–94, 2002. © 2002 Wiley‐Liss, Inc.