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R G Kalb

Publications and source records attributed to R G Kalb.

At least 19 recordsLinked to original sources
PubMed1997

Sensitization to morphine induced by viral-mediated gene transfer.

Repeated administration of morphine sensitizes animals to the stimulant and rewarding properties of the drug. It also selectively increases expression of GluR1 (an AMPA glutamate receptor subunit) in the ventral tegmental area, a midbrain region implicated in morphine action. By viral-mediated gene transfer, a causal relation is shown between these behavioral and biochemical adaptations: Morphine's stimulant and rewarding properties are intensified after microinjections of a viral vector expressing GluR1 into the ventral tegmental area. These results confirm the importance of AMPA receptors in morphine action and demonstrate specific locomotor and motivational adaptations resulting from altered expression of a single localized gene product.

Animals↗
PubMed1997

Synchronized overproduction of AMPA, kainate, and NMDA glutamate receptors during human spinal cord development.

Quantitative receptor autoradiography was used to map the distribution in the developing human spinal cord of the three types of ionotropic glutamate receptors. N-methyl-D-Aspartate (NMDA) receptors were labeled with [3H]glutamate, kainic acid (KA) receptors were labeled with [3H]KA, and alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) receptors were labeled with [3H]AMPA. In the adult, labeling of all three receptor subtypes is largely restricted to the substantia gelatinosa (SG) in the dorsal horn, with very low level labeling elsewhere in the spinal gray matter. In marked distinction, in late fetal life, high level ligand binding is seen throughout the spinal gray matter. In early postnatal life, binding sites diminish in all regions, but least so in the SG, until the adult pattern emerges. Thus a coordinated transient high level of ionotropic glutamate receptor expression occurs within the developing spinal cord. Saturation analysis of ligand binding shows that the affinity of [3H]KA and [3H]AMPA binding is not developmentally regulated. In contrast, the affinity of [3H]glutamate binding to the NMDA receptor in the fetal ventral horn is three-fold greater than in the adult ventral horn. Thus, in addition to quantitative changes in glutamate receptor expression, qualitative changes occur in the expression of NMDA receptors during development. The distinct glutamate receptor phenotype of fetal and early postnatal spinal cord cells suggests that alterations in the excitable properties of these cells plays an important role in activity-dependent development and in susceptibility to excitotoxic injury.

Adolescent↗
PubMed1997

Introduction of the glutamate receptor subunit 1 into motor neurons in vitro and in vivo using a recombinant herpes simplex virus.

We developed and characterized a recombinant herpes simplex virus vector and used it to introduce the complementary DNA encoding glutamate receptor subunit 1 flip into postmitotic motor neurons. Infection of purified motor neurons in vitro with this vector resulted in selective, high-level expression of glutamate receptor subunit 1 immunoreactivity in nearly 100% of the neurons. Patch-clamp experiments demonstrated that the protein product of the glutamate receptor subunit 1 flip transgene assembles into functional alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor channels. Herpes simplex virus-glutamate receptor subunit 1 flip was introduced into spinal cord cells by direct injection into the ventral horn and selectively into motor neurons by sciatic nerve injection. High levels of expression were sustained for at least one week and were accompanied by changes in the ionic permeability of AMPA receptors in transgene-expressing neurons. Throughout the first week of infection, there was little evidence for toxicity. Herpes simplex virus provides a versatile tool for manipulating the glutamate receptor phenotype of postmitotic neurons and will permit study of the role of individual glutamate receptor subunits in neuronal physiology and pathophysiology.

Animals↗
PubMed1995

NMDA antagonism during development extends sparing of hindlimb function to older spinally transected rats.

Hindlimb weight support and bipedal stepping occur after spinal cord transection in neonatal rats (birth to 12 days of age) while the same lesion in 15-day and older animals results in permanent loss of these responses. Some compensatory change in lumbar spinal circuitry must occur after spinal transection in young animals subserving these hindlimb behaviors. In contrast, animals just a few days older are incapable of such compensatory responses. We have examined the hypothesis that neural activity leads to the postnatal loss of plasticity in spinal circuitry. We find that antagonism of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor with MK-801 in young animals extends the sparing of hindlimb function after spinal transection to older animals. This effect is not due to a non-specific depression of all exciatory drive to motor neurons since Ia to motor neurons synaptic transmission through non-NMDA receptors is preserved during MK-801 treatment. Acute administration of MK-801 at the time of spinal transection or chronic administration of MK-801 after postnatal day 17 has no effect on recovery of hindlimb function after spinal transection. These results highlight the importance of NMDA receptor activation in spinal circuit maturation.

Aging↗
PubMed1995

Quantitative and qualitative changes in AMPA receptor expression during spinal cord development.

Synaptic activity in early postnatal life is important for the acquisition of mature structural and functional properties of neurons. Previous studies indicate that the mature molecular features of spinal motor neurons emerge during a period of activity-dependent development in early postnatal life. Since glutamatergic synaptic transmission provides the major excitatory drive into motor neurons, glutamate receptors are likely to play a central role in motor neuron activity-dependent development. To gain insight into this process, we have used receptor autoradiography, immunoblotting and immunohistochemistry to determine the distribution, temporal expression and potential subunit composition of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid subtype glutamate receptors in the developing rat spinal cord. Using two different ligands, [3H]-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and [3H]-6-cyano-7-nitroquinoxaline-2,3-dione, we find that alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid binding sites in the adult are largely restricted to the substantia gelatinosa. In marked contrast, during early postnatal life, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid binding sites are transiently expressed at high levels in the ventral horn. This parallels previous findings on the developmental regulation of N-methyl-D-aspartate receptor expression. Using alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit-specific antibodies we show by immunoblot analysis and immunohistology that, to varying degrees, the expression patterns of glutamate receptor subunit 1 and glutamate receptor subunits 2/3 are significantly developmentally regulated. The most conspicuous change is the downregulation of glutamate receptor 1 expression within motor neurons over the first three weeks of postnatal life. The qualitative and quantitative changes we observe in glutamate receptor expression in early postnatal life are likely to have a major impact on the electrophysiological properties of young motor neurons and thus may contribute to their activity-dependent development.

Animals↗
PubMed1995

In situ hybridization analysis of AMPA receptor subunit gene expression in the developing rat spinal cord.

In early postnatal life the acquisition of mature morphological and molecular features of motor neurons is influenced by synaptic activity within the spinal cord. Glutamatergic synaptic neurotransmission is believed to play a central role in this process. We hypothesize that the repertoire of glutamate receptors expressed by neurons in the young spinal cord differ from those expressed in adults and such receptors support activity-dependent developmental plasticity. To explore this idea, we used in situ hybridization histochemistry to determine the distribution, temporal expression, and potential subunit composition of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the developing rat spinal cord and compared these findings with those in adult rats. We find qualitative and quantitative changes in alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit gene expression over the first month of postnatal life. alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit genes GluR1, 2 and 4 are expressed at greater levels throughout the spinal cord of the neonate versus the adult animals. The developmental down-regulation is most pronounced for GluR1 transcripts, less for GluR2 and GluR4 transcripts, and minimal for GluR3 transcripts. Analysis of flip and flop splice variants of each subunit show that receptors expressed by adult motor neurons are potentially composed of the subunits GluR1 flop, GluR2 flip, GluR3 flip and flop, and GluR4 flip. In neonatal motor neuron all subunits are potentially expressed (except GluR2 flop) with quantitatively the dominent subunits being the flip splice variants of GluR1, 2 and 4. Receptors in the substantia gelatinosa undergo equally dramatic, developmentally independent changes. Changes in the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit composition are likely to have an important effect on the electrophysiological properties of motor neurons and may form part of the molecular identity of neurons capable of undergoing activity-dependent developmental plasticity.

Animals↗
PubMed1994

Electrical activity in the neuromuscular unit can influence the molecular development of motor neurons.

During the first few weeks of postnatal life spinal motor neurons develop electrophysiological, morphological, and molecular features that are characteristic of adult motor neurons. To understand how the acquisition of the mature neuronal phenotype is regulated, we have examined the expression of the motor neuron cell surface proteoglycan recognized by monoclonal antibody Cat-301 in the hamster. Previously we found that Cat-301 immunoreactivity is not present on motor neurons at birth and that by the end of the second postnatal week all motor neurons are Cat-301-positive. Surgical and pharmacological lesion studies have shown that the onset of Cat-301 expression depends upon input from both large-diameter primary afferents and from supraspinal afferents. Once the Cat-301 proteoglycan is expressed on motor neurons, its continued expression is independent of these inputs. These studies suggested that motor neuron maturation depends upon the coordination of several afferent inputs during the first postnatal weeks of life. Our previous studies could not address whether segmental and descending afferents (i) provide a chemical signal (such as a trophic factor) or (ii) confer a pattern of neuronal activity upon motor neurons that then results in the expression of the Cat-301 proteoglycan. The present experiments examine the role of electrical activity in motor neuron maturation. In normal animals, all sciatic motor neurons are Cat-301-positive by Postnatal Day 19 (P19). Chronic application of the sodium channel blocker, tetrodotoxin (TTX), to the sciatic nerve in neonatal animals reduces the percentage of Cat-301-positive motor neurons found at P21 by one-third. This reduction is not due to a nonspecific inhibition of all protein synthesis, because the expression of two other motor neuron antigens proceeds normally in TTX-treated neonates. Blockade of neuromuscular transmission in neonates by Botulinus toxin A also reduces the percentage of Cat-301-positive motor neurons. Cat-301 expression is not tied simply to neuronal activity, because chronic application of TTX to the sciatic nerve, or Botulinus toxin A to muscles, in the adult does not reduce Cat-301 expression. These findings indicate that electrical activity generated within the neuromuscular unit in early postnatal life can influence the acquisition of mature molecular properties by motor neurons.

Action Potentials↗
PubMed1994

Regulation of motor neuron dendrite growth by NMDA receptor activation.

Spinal motor neurons undergo great changes in morphology, electrophysiology and molecular composition during development. Some of this maturation occurs postnatally when limbs are employed for locomotion, suggesting that neuronal activity may influence motor neuron development. To identify features of motor neurons that might be regulated by activity we first examined the structural development of the rat motor neuron cell body and dendritic tree labeled with cholera toxin-conjugated horseradish peroxidase. The motor neuron cell body and dendrites in the radial and rostrocaudal axes grew progressively over the first month of life. In contrast, the growth of the dendritic arbor/cell and number of dendritic branches was biphasic with overabundant growth followed by regression until the adult pattern was achieved. We next examined the influence of neurotransmission on the development of these motor neuron features. We found that antagonism of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor inhibited cell body growth and dendritic branching in early postnatal life but had no effect on the maximal extent of dendrite growth in the radial and rostrocaudal axes. The effects of NMDA receptor antagonism on motor neurons and their dendrites was temporally restricted; all of our anatomic measures of dendrite structure were resistant to NMDA receptor antagonism in adults. These results suggest that the establishment of mature motor neuron dendritic architecture results in part from dendrite growth in response to afferent input during a sensitive period in early postnatal life.

2-Amino-5-phosphonovalerate↗
PubMed1993

Painless aortic dissection presenting as a progressive myelopathy.

We report a patient with a painless aortic dissection whose neurologic symptoms progressed over 5 days to a complete transverse myelopathy. She did not experience pain as her neurologic deficits evolved. Magnetic resonance imaging revealed a thoracic aortic dissection extending from the arch to the level of the 12th thoracic vertebra and demonstrated ischemic changes in the spinal cord and one thoracic vertebral body. Aortic dissection must be included in the differential diagnosis of spinal cord syndromes even in the absence of pain. Early recognition of aortic dissection as a cause of progressive myelopathy may become increasingly important as new therapies for central nervous system ischemia are developed.

Aged↗
PubMed1993

Molecular evidence for nitric oxide-mediated motor neuron development.

The complex morphological, electrophysiological and molecular properties of the adult vertebrate nervous system emerge over an extended period in prenatal and early postnatal life. Numerous studies have shown that synaptic activity plays a key role in the postnatal acquisition of mature neuronal phenotype. The cellular and molecular mechanisms subserving activity-dependent development are largely unknown. Several lines of evidence suggest that a rise in intracellular Ca2+ as a consequence of synaptic activity may regulate neuronal differentiation through its interactions with calcium-activated signal transduction molecules such as calcium/calmodulin kinase type II, protein kinase C or nitric oxide synthase (NOS). The aim of the present study is to identify potential signal transduction events subserving postnatal motor neuron development. Here we show that NOS antagonists block the molecular maturation of motor neurons and this effect is likely to be mediated by a subpopulation of ventral horn cells that express NOS transiently during early postnatal life. These results suggest that the local production of nitric oxide within the ventral horn may contribute to a late phase in motor neuron differentiation.

Amino Acid Oxidoreductases↗
PubMed1993

Activity-dependent structural changes during neuronal development.

Activity during the early postnatal period can have a pronounced effect on the structure of neurons in the central nervous system. Recent studies in the cat visual system and in the vertebrate and invertebrate neuromuscular system, have provided new insights into the cellular and molecular features of this process.

Animals↗
PubMed1992

N-methyl-D-aspartate receptors are transiently expressed in the developing spinal cord ventral horn.

Quantitative receptor autoradiography was used to map the distribution of N-methyl-D-aspartate (NMDA) receptors in the developing rat spinal cord. Three different specific ligands, which label partially overlapping subpopulations of NMDA receptors, were used: an agonist (L-[3H]glutamate), a noncompetitive antagonist ([3H]MK-801), and a competitive antagonist ([3H]CGP-39653). In the adult, NMDA receptors labeled with all three ligands are restricted to the substantia gelatinosa in the spinal dorsal horn. In marked distinction, at postnatal day 7 NMDA receptors labeled with L-[3H]glutamate and [3H]MK-801 are present throughout the spinal gray matter. NMDA receptors in the neonatal spinal ventral horn have a higher affinity for L-[3H]glutamate than those in the adult substantia gelatinosa. Over the second and third postnatal weeks, NMDA receptors are lost from all areas of the spinal gray matter except for the substantia gelatinosa. Neonatal NMDA receptors identified with [3H]CGP-39653 are restricted to the substantia gelatinosa. These results show that the immature ventral horn contains a subpopulation of NMDA receptors and raise the possibility that motor neurons transiently express NMDA receptors in early postnatal life. Ventral horn NMDA receptors may be a component of the mechanisms by which the mature phenotype of motor neurons is acquired through activity-dependent processes. The loss of NMDA receptors over the course of development may play a role in limiting the period of motor neuron plasticity.

2-Amino-5-phosphonovalerate↗
PubMed1991

Induction of demyelination by intraneural injection of antibodies against sulfoglucuronyl paragloboside.

Sulfoglucuronyl glycolipids (SGGLs) carry the glucuronyl 3-sulfate (HNK-1) epitope which is recognized by monoclonal IgM paraproteins from patients with demyelinating polyneuropathy. We report that intraneural injections of rat anti-SGGL antibodies induce demyelination in rat sciatic nerve, along with mild to moderate clinical symptoms. Morphologically, vesiculation and loosening of the myelin sheath were observed 3 h postinjection, followed by extensive demyelination and macrophage infiltration after 4 days. Since the anti-SGGL antibodies showed no cross-reactivity with other components in rat sciatic nerve, these results indicate that SGGLs alone can serve as the target antigens in demyelinating neuropathy.

Animals↗
PubMed1990

Induction of a neuronal proteoglycan by the NMDA receptor in the developing spinal cord.

Activation of the N-methyl-D-aspartate (NMDA) subclass of glutamate receptors is a critical step in the selection of appropriate synaptic connections in the developing visual systems of cat and frog. Activity-dependent development of mammalian motor neurons was shown to be similarly mediated by activation of the NMDA receptor. The expression of the Cat-301 proteoglycan on motor neurons was developmentally regulated and could be specifically inhibited by blockade of the NMDA receptor at the spinal segmental level. In the adult, Cat-301 immunoreactivity on motor neurons was not diminished by NMDA receptor blockade. The NMDA receptor may regulate the expression of a class of neuronal proteins (of which Cat-301 is one example) that underlie the morphological and physiological features of activity-dependent development.

Aging↗
PubMed1990

Large diameter primary afferent input is required for expression of the Cat-301 proteoglycan on the surface of motor neurons.

The expression of a cell surface proteoglycan, recognized by monoclonal antibody Cat-301, is regulated by neuronal activity in early life. Here we report that the expression of the Cat-301 proteoglycan on motor neurons depends on primary afferent input in the early postnatal period. Previously we showed that in two different systems, Y-cells in the cat lateral geniculate nucleus and motor neurons in the hamster spinal cord, the expression of the Cat-301 antigen requires neuronal activity during a circumscribed period in development. Disrupting the activity of Y-cells (by dark rearing or by monocular lid suture) or of motor neurons (by sciatic nerve crush or by spinal cord lesion) during the early postnatal period prevents Cat-301 expression. Disrupting neuronal activity in adults has no effect on Cat-301 expression. The onset of Cat-301 expression corresponds to the end of the period of activity-dependent development. In order to further dissect the components of the segmental reflex are required for the expression of Cat-301 on motor neurons, here we evaluated the effect of deafferentation by dorsal rhizotomy. In adult animals two weeks after deafferentation all sciatic motor neurons continue to express Cat-301. In contrast, in neonates two weeks after deafferentation the normal developmental expression of Cat-301 is reduced and less than 50% of sciatic motor neurons express Cat-301. We next selectively lesioned the small diameter afferents using the neurotoxin capsaicin. In contrast to rhizotomy, neonatal deletion of small diameter afferents has no effect on the development of Cat-301 expression on motor neurons. These results imply that input relayed by large diameter primary afferents (probably those conveying muscle and/or joint information) is required for normal maturation of motor neuronal properties during early life. They also provide further evidence for activity-dependent maturation of motor neurons.

Animals↗
PubMed1989

Characterization of an activity-dependent, neuronal surface proteoglycan identified with monoclonal antibody Cat-301.

Monoclonal antibody Cat-301 was previously shown to recognize a surface-associated antigen on subsets of mammalian CNS neurons whose expression is regulated by neuronal activity early in an animal's postnatal life. We now present the partial purification and characterization of the Cat-301 antigen and demonstrate that it is a chondroitin sulfate proteoglycan. Extracellular localization of the Cat-301 epitope is demonstrated by staining live, intact neurons in situ. Extraction of the antigen from membranes in the absence of detergent indicates that it is either a peripheral membrane protein or a component of an extracellular matrix. The Cat-301 antigen migrates on Western blots of SDS gels with a molecular weight of integral of 680,000 dalton and is purified by DEAE chromatography and Sepharose gel filtration in 8 M urea (pH 4.9) buffer. The antigen is sensitive to chondroitinase ABC, indicating that it is a chondroitin sulfate proteoglycan. Furthermore, we provide strong evidence that the biochemically characterized antigen is indeed the histologically detected species by using a second antibody, Cat-304, that produces immunohistological staining patterns identical to those of Cat-301 and reacts with the purified antigen, but at a distinct epitope. Our earlier developmental findings and the present localization and biochemical results suggest that the antigen may play a role in the maturation of functional connections between neurons, perhaps through stabilization of axosomatic and axodendritic synapses.

Animals↗
PubMed1988

Molecular evidence for early activity-dependent development of hamster motor neurons.

Monoclonal antibody Cat-301 recognizes a surface antigen on subsets of neurons in many areas of the mammalian CNS, including Y-cells in the cat dorsal lateral geniculate nucleus (LGN) and spinal motor neurons in several species. We have shown previously that the Cat-301 antigen is expressed relatively late in postnatal development, with a time course that matches that of late developmental features of both LGN and spinal cord neurons. The developmental time course of the expression of the Cat-301 antigen in the LGN correlates with the period during which visual deprivation can alter LGN Y-cells. Neonatal visual deprivation (by monocular lid suture or dark rearing) suppresses Cat-301 expression on Y-cells, while deprivation in adult animals has no effect on antigen expression. These results suggested that the onset of Cat-301 immunoreactivity provides a positive molecular marker for the end of a critical period in cat visual system development. To determine if Cat-301 might be a general marker for experience-dependent development in other areas of the CNS we have examined antigen expression on hamster spinal cord motor neurons. Here, we report that Cat-301 immunoreactivity develops on hamster motor neurons between postnatal days 7 and 14. Altering neuromuscular activity by sciatic nerve crush or thoracic hemicordotomy inhibits Cat-301 expression on motor neurons if performed before the onset of Cat-301 immunoreactivity. Other motor neuron antigens are unaffected by this procedure. In adult animals, nerve crush or cordotomy has no effect on Cat-301 immunoreactivity, demonstrating that Cat-301 expression is not simply dependent on ongoing neural activity. These observations suggest that motor neurons, like LGN neurons, require some pattern of neuronal activity during a critical period in development and, further, that the phenotypic changes in neurons consequent to early activity are reflected by the expression of specific molecules. The identification and characterization of such molecules may yield a description of the molecular mechanisms of experience-dependent development.

Aging↗