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C F Dreyfus

Publications and source records attributed to C F Dreyfus.

At least 55 records · Page 3Linked to original sources
PubMed1989

Expression of NGF and NGF receptor mRNAs in the developing brain: evidence for local delivery and action of NGF.

Nerve growth factor (NGF) is a well-documented target-derived trophic factor in the peripheral nervous system. Recently, proteins as well as mRNAs for both NGF and its receptor (NGF-R) have been detected in diverse areas in the central nervous system (CNS). Considerable evidence suggests that NGF also functions in the target synthesis/retrograde transport mode in the brain. For example, NGF is synthesized in the target hippocampus, as indicated by the presence of NGF message, and interacts with the receptors on terminals projecting from basal forebrain, where receptor mRNA is detectable. Spatial separation of NGF and receptor gene expression is consistent with the target mechanism of action. To ascertain whether local action may also occur in the CNS, we used sensitive nuclease protection assays to study the relationship of NGF and NGF-R expression in the developing brain. Our results indicate that in some brain areas, such as diencephalon, postnatal hippocampus, and olfactory bulb, NGF message was highly expressed, while receptor mRNA was virtually undetectable, suggesting that these areas serve as target sources of NGF for distant afferent neurons. By contrast, in other brain areas, such as cerebellum, striatum, perinatal olfactory bulb, and prenatal hippocampus, NGF and NGF-R mRNAs were coexpressed and coregulated developmentally. Consequently, local delivery and action of the trophic molecule may occur in these areas during these periods. We tentatively conclude that NGF may act through both distant and local modes in the developing CNS.

Animals↗
PubMed1989

Expression of high- and low-affinity nerve growth factor receptors by Purkinje cells in the developing rat cerebellum.

Mounting evidence indicates that nerve growth factor plays a role in the development and function of the basal forebrain-cerebral cortical system. In addition, recent studies indicate that nerve growth factor receptor messenger RNA is transiently detectable in whole cerebellum in the neonatal rat. We now report that cerebellar Purkinje cells express high-affinity and low-affinity nerve growth factor receptor sites, identified by 125I-NGF binding, in the postnatal Day 10 rat in vivo. The expression correlates with cerebellar development, suggesting that nerve growth factor may regulate the normal ontogeny of cerebellar Purkinje cells.

Animals↗
PubMed1989

Effects of nerve growth factor on cholinergic brain neurons.

Nerve growth factor (NGF) is a fully characterized molecule, well known for its actions in the differentiation and maintenance of peripheral neurons. However, recent studies suggest that its actions are not limited to the periphery, but may extend to the CNS. In particular, this trophic agent appears to affect development and survival of a variety of brain cell populations. Noteworthy are its actions on cholinergic neurons that degenerate in Alzheimer's disease and Huntington's chorea. However, studies of NGF receptor sites suggest that effects of NGF may also extend to non-cholinergic cell groups. Cheryl Dreyfus summarizes these data and points to future work necessary to define further the underlying mechanisms of action and to examine the function of NGF on diverse brain populations.

Animals↗
PubMed1989

GABAergic and cholinergic neurons exhibit high-affinity nerve growth factor binding in rat basal forebrain.

We have used dissociated, rat basal forebrain cultures to identify specific cell types that are potentially responsive to nerve growth factor (NGF). Expression of high-affinity NGF binding sites was examined. A subpopulation of cells containing choline acetyltransferase (CAT), the acetylcholine-synthesizing enzyme, exhibited high-affinity binding, employing combined immunocytochemistry and 125I-NGF radioautography. Unexpectedly, a gamma-aminobutyric acid (GABA)-containing cell group also expressed high-affinity binding. These cells that exhibit high-affinity binding appear to be neurons since they stain positively with the neuron marker, neuron-specific enolase, and negatively with the nonneuron marker, glial fibrillary acidic protein. Our observations suggest that NGF may regulate multiple brain systems and functions that have yet to be explored. Conversely, only subsets of cholinergic or GABA neurons expressed high-affinity binding, suggesting that these transmitter populations are composed of differentially responsive subpopulations.

Animals↗
PubMed1988

Substance K (NKA) increases tyrosine hydroxylase mRNA in cultured substantia nigra.

Cultured explants of the mouse substantia nigra were used to analyze mechanisms underlying the depolarization-induced increase in tyrosine hydroxylase activity. Steady-state levels of messenger RNA encoding tyrosine hydroxylase were detected using an antisense riboprobe in an RNase protection assay. Explants exposed to the depolarizing agent, veratridine, exhibited an approximate 2-fold increase in tyrosine hydroxylase messenger RNA. Moreover, the native presynaptic excitatory agonist substance K also elicited a significant increase in tyrosine hydroxylase message. We conclude that depolarizing influences induce tyrosine hydroxylase in the cultured substantia nigra in association with an elevation of enzyme messenger RNA.

Animals↗
PubMed1988

Localization of high-affinity and low-affinity nerve growth factor receptors in cultured rat basal forebrain.

Previous work has indicated that nerve growth factor specifically and selectively increases choline acetyltransferase and acetylcholinesterase in organotypic cultures of rat basal forebrain-medial septal area. To determine whether these actions are potentially receptor-mediated, organotypic and dissociated basal forebrain-medial septal area cultures were examined. Two independent methods, [125I]nerve growth factor binding and immunocytochemistry with a monoclonal nerve growth factor receptor antibody (192-IgG), detected specific receptors. The nerve growth factor receptors were localized to two different cellular populations: flat, large, non-neuron-like cells, and small, round, process-bearing, neuron-like cells. Dissociation studies with [125I]nerve growth factor suggested that high-affinity receptors were localized to the neuron-like population, while only low-affinity receptors were localized to the non-neuron-like cells. We tentatively conclude that nerve growth factor may elicit cholinergic effects by directly binding to high-affinity receptors on neurons. To begin examining receptor regulation, cultures were exposed to exogenous, unlabeled nerve growth factor continuously for 10 days before binding studies were performed. Prior exposure to nerve growth factor did not alter binding characteristics of the receptor, using the present methods.

Animals↗
PubMed1988

Presynaptic transmitters and depolarizing influences regulate development of the substantia nigra in culture.

Recent evidence suggests that extracellular signals regulate neurotransmitter traits in brain catecholaminergic (CA) neurons as in the periphery. Development of the dopaminergic phenotype in the mouse substantia nigra (SN) was studied by monitoring tyrosine hydroxylase (TH), the rate-limiting enzyme in CA biosynthesis in vivo and in culture. Explants of SN were dissected from embryonic day 15 embryos and grown in culture for a week. To define the influence of depolarizing signals on central dopaminergic neurons, cultures were grown with the pharmacologic depolarizing agent veratridine. This treatment elicited a significant increase in TH enzyme activity, accompanied by elevated levels of enzyme protein. The increase in activity was prevented by TTX, suggesting that transmembrane Na+ influx was necessary for the rise in TH. A physiologic presynaptic agonist, substance P, also evoked a significant increase in TH activity; however, the coproduced tachykinin peptide, substance K (SK, neurokinin A) elicited a more dramatic rise. The SK effect was blocked by TTX, suggesting that the physiologic agonist was acting through the same mechanism as the pharmacologic agent veratridine. Immunoblot analysis revealed that SK elicited a parallel increase in TH enzyme protein. Our observations suggest that the novel peptide, SK, serves a physiological role in the regulation of TH in the striatonigral pathway.

Animals↗
PubMed1987

Glucocorticoid effects on phenylethanolamine N-methyltransferase (PNMT) in explants of embryonic rat medulla oblongata.

Although glucocorticoid hormones have important roles in the development of neurotransmitter systems in cells derived from the neural crest, it is not known whether they have parallel effects on neuronal development in the brain. To address this issue, we have established an in vitro system of fetal medulla oblongata (MO) to follow development of the epinephrine-synthesizing enzyme, phenylethanolamine N-methyltransferase (PNMT). Embryonic MO was explanted from E13 or E18 embryos and maintained for up to 3 weeks. Successful culture of adrenergic neurons was possible only in explants taken from young embryos, since E18 explants failed to develop. In E13 explants, immunoreactivity to both PNMT and tyrosine hydroxylase, the rate limiting enzyme in catecholamine synthesis, was observed. PNMT catalytic activity which was barely detectable at the time of explanation increased markedly during the first week in vitro. To study the effects of glucocorticoids on PNMT development in central neurons, MO explants were grown in glucocorticoid deficient medium in which rat serum from adrenalectomized rats was substituted for human placental serum. Addition of natural glucocorticoids, cortisol or corticosterone, or the mineralcorticoid, deoxycorticosterone, during the third culture week had no effect on PNMT activity. Dexamethasone (DEX), a synthetic glucocorticoid, also had no effect on PNMT during the first or second weeks in culture. However, addition of DEX during the third culture week resulted in a doubling of PNMT activity. However, attempts to block the DEX effect during the third week or to block the increase in PNMT activity during the first week in control cultures with the glucocorticoid receptor antagonist, dexamethasone 21-mesylate, were unsuccessful. These results suggest that PNMT in central neurons does not require glucocorticoids for ontogeny during the embryonic period. This is in contrast to PNMT in adrenal medulla which requires glucocorticoids for normal development during both the embryonic and postnatal periods. More generally, these studies suggest that development of the same neurotransmitter phenotype in brain and periphery may be differentially regulated.

Animals↗
PubMed1987

Biochemistry of information storage in the nervous system.

The use of molecular biological approaches has defined new mechanisms that store information in the mammalian nervous system. Environmental stimuli alter steady-state levels of messenger RNA species encoding neurotransmitters, thereby altering synaptic, neuronal, and network function over time. External or internal stimuli alter impulse activity, which alters membrane depolarization and selectively changes the expression of specific transmitter genes. These processes occur in diverse peripheral and central neurons, suggesting that information storage is widespread in the neuraxis. The temporal profile of any particular molecular mnemonic process is determined by specific kinetics of turnover and by the geometry of the neuron resulting in axonal transport of molecules to different synaptic arrays at different times. Generally, transmitters, the agents of millisecond-to-millisecond communication, are subject to relatively long-lasting changes in expression, ensuring that ongoing physiological function is translated into information storage.

Adrenal Medulla↗
PubMed1987

Nerve growth factor selectively increases cholinergic markers but not neuropeptides in rat basal forebrain in culture.

We have previously used organotypic cultures to study mechanisms regulating phenotypic expression of neurotransmitter characters in the brain. Our previous work indicated that nerve growth factor (NGF) specifically increased the activity of choline acetyltransferase (CAT) in striatal cholinergic interneurons. In the present study we examined the effect of NGF on neurons of fetal rat basal forebrain-medial septal area (BF-MS) maintained in organotypic culture. Treatment with 200 biological units/ml of NGF resulted in a 3- to 6-fold increase in the specific activity of CAT. This effect was specifically blocked by anti-NGF antiserum, whereas treatment with antiserum alone did not alter the cholinergic enzyme. NGF also elicited a marked increase in CAT staining intensity, using a monoclonal antibody directed against the enzyme. Further, the number of CAT-positive neurons appeared to increase in the NGF-treated cultures. Exposure to NGF also increased the activity of another cholinergic marker, the catabolic enzyme, acetylcholinesterase. The effect of NGF appeared to be highly selective, since substance P and somatostatin levels were unchanged by NGF treatment.

Acetylcholinesterase↗
PubMed1986

Depolarizing stimuli increase tyrosine hydroxylase in the mouse locus coeruleus in culture.

The influence of membrane depolarization on the development and regulation of brain noradrenergic neurons was studied in explant cultures of the mouse locus coeruleus (l.c.). Exposure to the depolarizing agents veratridine or elevated K+ significantly increased the catalytic activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. The effects of veratridine were prevented by tetrodotoxin, suggesting that transmembrane Na+ influx was necessary for the rise in TH. Morphometric analysis indicated that the rise in TH activity was not accompanied by altered TH-positive cell number or cell diameter. Rather, TH fluorescence intensity increased in each neuron, suggesting that depolarization increased TH per neuron. Immunoblot and densitometric analysis indicated that depolarization did, indeed, increase TH immunoreactive protein. Moreover, depolarization elevated enzyme activity in cultured neurons expressing the normal developmental increase in TH, as well as those in which plateau levels had already been attained. We conclude that depolarization and/or Na+ influx regulates a critical transmitter macromolecule in brain neurons, as in the periphery, by altering enzyme molecule number.

Animals↗
PubMed1985

Selective expression of high-affinity uptake of catecholamines by transiently catecholaminergic cells of the rat embryo: studies in vivo and in vitro.

Transient expression of catecholaminergic phenotypic traits is a widespread phenomenon during embryonic development in mammals, occurring in cells of the embryonic gut mesenchyme, in ventrolateral portions of the neural tube, cells of cranial sensory and dorsal root ganglia, and in the embryonic pancreas. In the current study the manifestation of the catecholamine (CA) phenotype in these populations has been further defined. Specifically, the existence of the high-affinity uptake process for CAs in these populations has been investigated. By combining the techniques of radioautography following accumulation of [3H]norepinephrine (3H-NE) and [3H]dopamine (3H-DA) with immunohistochemical detection of tyrosine hydroxylase (T-OH), it has been possible to demonstrate simultaneously CA accumulation by T-OH-positive gut cells. Uptake of 3H-NE was first detected in T-OH-positive cells of the gut on gestational day 12.5 (E12.5). By contrast, T-OH immunoreactivity was first detected on E11.5. By E13.5 virtually every T-OH-positive cell oral to the umbilical flexure was radioautographically labeled. Uptake at E13.5 displayed Michaelis-Menten saturation kinetics, had a Vmax of 35 fmole/gut/min, a Km of 1.45 microM, was blocked by desmethylimipramine (DMI), and by incubation at 4 degrees C. On subsequent gestational days, silver grains marking areas of amine concentration were found increasingly over T-OH-negative cells. A similar pattern of uptake was found in guts which had been grown in organotypic tissue culture for the purpose of eliminating extrinsic sympathetic innervation. T-OH-positive gut cells also accumulated 3H-DA. Concentration of 3H-DA was blocked by both benztropine and DMI suggesting that accumulation had properties common to both NE and DA systems. By contrast to cells of the gut, accumulation of CAs was not a property of transiently T-OH-positive cells in other locations. Therefore, specific, high-affinity uptake and retention of CAs is an additional property of transiently catecholaminergic gut cells. Appearance of CA synthetic enzymes precedes the appearance of the CA storage process in cells of the gut. Persistence of the uptake process after the loss of detectable T-OH suggests continued viability of the population. The absence of CA accumulation by other T-OH-positive cells suggests basic molecular differences among the various populations.

Animals↗
PubMed1985

Nerve growth factor promotes cholinergic development in brain striatal cultures.

We have examined the effect of the trophic protein, nerve growth factor (NGF), on organotypic cultures of fetal rat striatum. Treatment of cultures with NGF for 10-11 days resulted in a 5- to 12-fold increase in the specific activity of the cholinergic enzyme choline acetyltransferase (CAT; EC 2.3.1.6). in a dose-dependent fashion. This effect was not elicited by insulin, ferritin, or cytochrome c, proteins similar in structure or physicochemical properties to NGF. The effect of NGF on CAT activity was specifically blocked by anti-NGF antiserum, whereas treatment with the antiserum alone did not have a significant effect on the enzyme. Immunocytochemical studies of the treated cultures, using a monoclonal antibody directed against CAT, revealed positively stained neurons exhibiting dendritic and axonal processes. NGF did not have an effect on total protein content of the striatal cultures, suggesting a highly specific effect. Moreover, levels of substance P, a peptide localized to other, noncholinergic neurons, were not altered by NGF. Substance P remained unchanged after treatment with NGF for 12 days, whereas CAT activity increased 12-fold in sister cultures. Although the mechanisms of action of NGF on striatal cholinergic interneurons remain to be determined, the marked, specific response of CAT suggests that this well-defined trophic protein may play a critical role in normal brain development.

Animals↗
PubMed1984

Neurotransmitter plasticity at the molecular level.

Contrary to long-held assumptions, recent work indicates that neurons may profoundly change transmitter status during development and maturity. For example, sympathetic neurons, classically regarded as exclusively noradrenergic or cholinergic, can also express putative peptide transmitters such as substance P. This neuronal plasticity is directly related to membrane depolarization and sodium ion influx. The same molecular mechanisms and plastic responses occur in mature as well as developing neurons. Further, contrary to traditional teaching, adult primary sensory neurons may express the catecholaminergic phenotype in vivo. Transmitter plasticity is not restricted to the peripheral nervous system: ongoing studies of the brain nucleus locus ceruleus in culture indicate that specific extracellular factors elicit marked transmitter changes. Consequently, neurotransmitter expression and metabolism are dynamic, changing processes, regulated by a variety of defined factors. Transmitter plasticity adds a newly recognized dimension of flexibility to nervous system function.

Adrenal Medulla↗
PubMed1983

Development of catecholaminergic phenotypic characters in the mouse locus coeruleus in vivo and in culture.

While abundant studies have begun to elucidate ontogeny of the peripheral nervous system, molecular mechanisms underlying brain development remain obscure. To approach this problem, we initiated parallel in vivo and in vitro studies of the mouse locus coeruleus (l.c.), a brainstem noradrenergic nucleus. The catecholaminergic enzymes tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) were used to monitor phenotype expression and development. TH catalytic activity and immunocytochemical reactivity were initially detectable on gestational Day 13 (E-13) in vivo, and adult levels of activity were approximately by the third postnatal week. Immunotitration studies indicated that the developmental increase was due to accumulation of enzyme molecules and not enzyme activation. The in vivo developmental profile of DBH approximated that of TH. To begin defining regulatory mechanisms, explants of embryonic brainstem were placed in culture. Explantation on E-12, prior to expression of TH or DBH, resulted in the de novo appearance of these phenotypic characters after 4 days. Explantation on E-18, after the enzymes are already expressed, was followed by a striking sixfold rise in TH activity. Immunotitration studies revealed that the increase in TH activity in E-18 cultures was attributable to increased molecule number, reproducing the in vivo results. Moreover, the E-18 explants, cultured for 3 weeks, attained higher plateau levels of TH activity than E-12 cultures, and this differences was due to increased molecule number. Morphometric analysis indicated that 3-week E-12 cultures actually had more l.c. cells than E-18 cultures, indicating that differences in TH were not due to increased cells in the E-18 l.c. Finally, systemic study revealed that the development of TH activity in culture increased progressively from E-11 to E-12 to E-13, suggesting that critical regulatory events occur at this time. Our studies suggest that the l.c. is an excellent model for the study of brain development in vivo and in vitro. Initial phenotypic expression and dramatic development occur in culture in the absence of normal targets, normal afferent innervation and, presumably, normal humoural milieu.

Animals↗
PubMed1980

Effects of indolic neurotoxins on enteric serotonergic neurons.

The effects of the indolic neurotoxins 5,6- and 5,7-dihydroxytryptamine (5,6-DHT; 5,7-DHT) on the enteric nervous system were examined. 5,6-DHT, in moderate dosage, 40 mg/kg, decreased uptake of tritiated 5-hydroxytryptamine (3H-5-HT) but not that of tritiated norepinephrine (3H-NE). However, selectivity of the neurotoxins for enteric serotonergic rather than adrenergic axons was enhanced by pretreating animals with desmethylimipramine to inhibit the catecholamine uptake mechanism. When this was done, 5,7-DHT was found to prevent the development of 5-HT histofluorescence (following injection of L-tryptophan) without affecting histofluorescence of NE. In contrast, 6-hydroxydopamine virtually abolished NE histofluorescence and uptake of 3H-NE without affecting development of 5-HT histofluorescence or uptake of 3H-5-HT. Electron microscopy revealed that b,7-DHT induced dose-dependent lesions of axonal varicosities in the enteric nervous system. Early lesions, 1--4 hours following injection, resembled cytolysosomes and consisted of membrane enclosed regions of opaque cytoplasm containing synaptic vesicles. Affected varicosities contained a mixed population of large dense cored (approximately 120 nm) and small lucent vesicles (approximately 70 nm) but none exhibited pre- or postsynaptic membrane specializations. After 24 hours terminals degenerated and were engulfed by surrounding supporting cells. It is concluded that peripheral serotonergic neurons resemble central serotonergic neurons in susceptibility to the toxic effects of indolic neurotoxins. These neurotoxins are useful anatomical markers of serotonergic terminal varicosities.

5,6-Dihydroxytryptamine↗