Biomedical subjects

G Leanza

Publications and source records attributed to G Leanza.

At least 19 recordsLinked to original sources

PubMed2005

Maternal exposure to the antiepileptic drug vigabatrin affects postnatal development in the rat.

The objective was to investigate, in the rat, the effects of maternal exposure to vigabatrin (VGB) on the postnatal motor-cognitive behaviour of the offspring. We used an experimental evaluator-blind, placebo-controlled study in the rat. Ten pregnant rats were divided into five groups and treated with different doses of VGB (250, 500, 750, 1000 mg/kg/day) or placebo from gestation day (GD) 6 to GD10. After delivery, 56 pups (40 pups prenatally exposed to VGB and 16 pups exposed to placebo) were evaluated for motor-cognitive behaviour throughout postpartum day 40. At the end of testing sessions the animals were sacrificed and brain tissues processed for biochemical analysis of GABA levels. Body weight of pups and young rats whose mothers were treated with a dose of 750 mg/kg/day were significantly lower both at birth and during the whole postnatal life with respect to the control groups. Young rats of this group exhibited impaired performance in both the open-field and water maze tasks. Brain GABA contents were dramatically increased in this group of rats. No other significant nutritional, biochemical or behavioural changes were observed after treatments with doses of VGB lower than 750 mg/kg/day. The exposure to a dose of 1000 mg/kg caused abortion. Maternal exposure to VGB at relatively high doses (750 mg/kg/day) is likely to cause some important changes of the nutritional status during the pre- and postnatal life. Thus, the biochemical and cognitive abnormalities observed in this study could be related to some disturbances of brain development induced by malnutrition and/or to a disturbance of neuronal programming of the gabaergic system.

Animals↗

PubMed2005

Selective cholinergic immunolesioning affects synaptic plasticity in developing visual cortex.

Cholinergic neurotransmission is known to affect activity-dependent plasticity in various areas, including the visual cortex. However, relatively little is known about the exact role of subcortical cholinergic inputs in the regulation of plastic events in this region during early postnatal development. In the present study, synaptic transmission and plasticity in the developing visual cortex were studied following selective immunotoxic removal of the basal forebrain cholinergic afferents in 4-day-old rat pups. The lesion produced dramatic cholinergic neuronal and terminal fibre loss associated with decreased mRNA levels for the M1 and M2 muscarinic receptors, as well as clear-cut impairments of long-term potentiation (LTP) in visual cortex slices. Indeed, after theta burst stimulation of layer IV a long-term depression (LTD) instead of an LTP was induced in immunolesioned slices. This functional change appears to be due to the lack of cholinergic input as exogenous application of acetylcholine prevented the shift from LTP to LTD. In addition, lesioned rats showed an increased sensitivity to acetylcholine (ACh). While application of 20 microm ACh produced a depression of the field potential in immunolesioned rat slices, in order to observe the same effect in control slices we had to increase ACh concentration to up to 200 microm. Taken together, our results indicate that deprivation of cholinergic input affects synaptic transmission and plasticity in developing visual cortex, suggesting that the cholinergic system could play an active role in the refinement of the cortical circuitry during maturation.

Acetylcholine↗

PubMed2001

Septal cholinergic neurons suppress seizure development in hippocampal kindling in rats: comparison with noradrenergic neurons.

Widespread lesions of forebrain cholinergic or noradrenergic projections by intraventricular administration of 192 IgG-saporin or 6-hydroxydopamine, respectively, accelerate kindling epileptogenesis. Here we demonstrate both quantitative and qualitative differences between the two lesions in their effects on hippocampal kindling in rats. Epileptogenesis was significantly faster after noradrenergic as compared to cholinergic denervation, and when both lesions were combined, kindling development resembled that in animals with 6-hydroxydopamine lesion alone. Furthermore, whereas the 192 IgG-saporin lesion promoted the development only of the early stages of kindling, administration of 6-hydroxydopamine or both neurotoxins accelerated the late stages also. To investigate the contribution of different subparts of the basal forebrain cholinergic system to its seizure-suppressant action in hippocampal kindling, 192 IgG-saporin was injected into medial septum/vertical limb of the diagonal band of Broca or nucleus basalis magnocellularis, leading to selective hippocampal or cortical cholinergic deafferentation, respectively. The denervation of the hippocampus facilitated kindling similar to the extensive lesion caused by intraventricular 192 IgG-saporin, whereas the cortical lesion had no effect. These results indicate that although both noradrenergic and cholinergic projections to the forebrain exert powerful inhibitory effects on hippocampal kindling epileptogenesis, the action of the cholinergic system is less pronounced and occurs specifically prior to seizure generalization. In contrast, noradrenergic neurons inhibit the development of both focal and generalized seizures. The septo-hippocampal neurons are responsible for the antiepileptogenic effect of the cholinergic system in hippocampal kindling, whereas the cortical projection is not significantly involved. Conversely, we have previously shown [Ferencz I. et al. (2000) Eur. J. Neurosci., 12, 2107-2116] that seizure-suppression in amygdala kindling is exerted through the cortical and not the hippocampal cholinergic projection. This shows that, depending on the location of the primary epileptic focus, i.e. the site of stimulation, basal forebrain cholinergic neurons operate through different subsystems to counteract seizure development in kindling.

Acetylcholine↗

PubMed2000

Basal forebrain neurons suppress amygdala kindling via cortical but not hippocampal cholinergic projections in rats.

Intraventricular administration of the immunotoxin 192 IgG-saporin in rats has been shown to cause a selective loss of cholinergic afferents to the hippocampus and cortical areas, and to facilitate seizure development in hippocampal kindling. Here we demonstrate that this lesion also accelerates seizure progression when kindling is induced by electrical stimulations in the amygdala. However, whereas intraventricular 192 IgG-saporin facilitated the development of the initial stages of hippocampal kindling, the same lesion promoted the late stages of amygdala kindling. To explore the role of various parts of the basal forebrain cholinergic system in amygdala kindling, selective lesions of the cholinergic projections to either hippocampus or cortex were produced by intraparenchymal injections of 192 IgG-saporin into medial septum/vertical limb of the diagonal band or nucleus basalis, respectively. Cholinergic denervation of the cortical regions caused acceleration of amygdala kindling closely resembling that observed after the more widespread lesion induced by intraventricular 192 IgG-saporin. In contrast, removal of the cholinergic input to the hippocampus had no effect on the development of amygdala kindling. These data indicate that basal forebrain cholinergic neurons suppress kindling elicited from amygdala, and that this dampening effect is mediated via cortical but not hippocampal projections.

Amygdala↗

PubMed1999

Release properties and functional integration of noradrenergic-rich tissue grafted to the denervated spinal cord of the adult rat.

Noradrenaline- (NA-) containing grafts of central (embryonic locus coeruleus, LC) or peripheral (juvenile adrenal medullary, AM, autologous superior cervical ganglionic, SCG) tissue were implanted unilaterally into rat lumbar spinal cord previously depleted of its NA content by 6-hydroxydopamine (6-OHDA) intraventricularly. A microdialysis probe was implanted in the spinal cord 3-4 months after transplantation, and extracellular levels of noradrenaline were monitored in freely moving animals during basal conditions and following administration of pharmacological or behavioural stimuli. Age-matched normal and lesioned animals both served as controls. Morphometric analyses were carried out on horizontal spinal sections processed for dopamine-beta-hydroxylase (DBH) immunocitochemistry, in order to assess lesion- or graft-induced changes in the density of spinal noradrenergic innervation, relative to the normal patterns. In lesioned animals, the entire spinal cord was virtually devoid of DBH-positive fibers, resulting in a dramatic 88% reduction in baseline NA, compared with that in controls, which did not change in response to the various stimuli. LC and SCG grafts reinstated approximately 80% and 50% of normal innervation density, respectively, but they differed strikingly in their release ability. Thus, LC grafts restored baseline NA levels up to 60% of those in controls, and responded with significantly increased NA release to KCl-induced depolarization, neuronal uptake blockade and handling. In contrast, very low NA levels and only poor and inconsistent responses to the various stimuli were observed in the SCG-grafted animals. In AM-grafted animals, spinal extracellular NA levels were restored up to 45% of those in controls, probably as a result of nonsynaptic, endocrine-like release, as grafted AM cells retained the chromaffine phenotype, showed no detectable fibre outgrowth and did not respond to any of the pharmacological or behavioural challenges. Thus, both a regulated, impulse-dependent, and a diffuse, paracrine-like, NA outflow may play roles in the recovery of lesion-induced sensory and/or motor impairments previously reported with these types of grafts following transplantation into the severed spinal cord.

Age Factors↗

PubMed1998

Chronic elevation of amyloid precursor protein expression in the neocortex and hippocampus of rats with selective cholinergic lesions.

Overexpression or aberrant processing of the beta-amyloid precursor protein (APP) and loss of cortical cholinergic function represent two hallmark pathological features of Alzheimer's disease, although it is still unclear whether these alterations take place independently or in an inter-related manner. In the present study, the possible relationships between altered APP expression and cholinergic hypofunction in the neocortex and hippocampus were addressed histologically following selective and complete (90-95%) removal of the basal forebrain cholinergic neurons by the 192 IgG-saporin immunotoxin, at a dose (5.0 microg, intraventricularly) producing profound and permanent cognitive deficits. Computer-aided densitometric analyses revealed, at 6 months post-lesion, a virtually complete loss of terminal cholinergic innervation in various neocortical and hippocampal regions (up to 80%), which correlated highly with the marked (up to 71%) increases in APP expression measured in the same territories. The present results indicate that the integrity of ascending basal forebrain cholinergic inputs to the neocortex and hippocampus may be required for the maintenance of physiological levels of APP expression in the same regions, thus providing a novel rationale for interventions aimed at restoring or enhancing cortical cholinergic neurotransmission.

Amyloid beta-Protein Precursor↗

PubMed1998

Extensive and permanent motoneuron loss in the rat lumbar spinal cord following neurotoxic lesion at birth: morphological evidence.

The efficacy of the neurotoxic lectin volkensin to induce motoneuron loss in the lumbar spinal cord was investigated at different time-points following unilateral injection into the medial gastrocnemius muscle of newborn (postnatal day 1 (PD 1)) animals, using retrograde fluorescent neuron labelling and histochemical procedures to evaluate the extent of the toxin-induced depletion, in comparison with the effects produced by neonatal crushing of the sciatic nerve. The results show that very low doses (2.0 ng) of volkensin intramuscularly can produce extensive (about 90%) and long-lasting (up to at least 8 months post-lesion) motoneuronal loss in the lumbar spinal cord, whose magnitude is higher than that observed following mechanical injury of the developing peripheral nerve (50-60%). Volkensin-induced motoneuronal depletion may therefore represent a useful model for experimental studies aimed at functional cell replacement in the immature spinal cord.

Aging↗

PubMed1998

Amelioration of spatial navigation and short-term memory deficits by grafts of foetal basal forebrain tissue placed into the hippocampus and cortex of rats with selective cholinergic lesions.

Impairments in learning and memory, induced by surgical or excitotoxic lesions of the septo-hippocampal or basalo-cortical pathways, can be ameliorated by grafts of cholinergic-rich foetal basal forebrain tissue into the hippocampus and/or neocortex. However, the effects of such grafts have been only partial, which may be due to the non-specific nature of the lesioning procedures used in these studies, known to destroy both cholinergic and non-cholinergic neuronal projections. In the present study, we have explored the effects of cholinergic-rich grafts in rats subjected to selective cholinergic lesions, induced by intraventricular injections of the immunotoxin 192 IgG-saporin. This lesion, which selectively destroyed 85-95% of the cholinergic neurons in both the septal-diagonal band and nucleus basalis, produced a long-lasting, substantial impairment in both the acquisition of spatial reference memory in the Morris water maze task and delay-dependent short-term memory performance, as seen in a delayed matching-to-position test. Foetal cholinergic grafts (but not control grafts of cerebellar tissue) implanted at multiple sites into both the hippocampus and fronto-parietal neocortex, bilaterally, completely reversed the acquisition deficit in place navigation in the water maze, to an extent that greatly exceeded that previously seen in animals with non-selective lesions. Most notably, however, the impairment in short-term memory was only partially and inconsistently affected, and only at the longest delay times. The morphological analysis, performed at about 7 months after transplantation, showed that the grafts had re-established a close to normal cholinergic innervation in the initially denervated cortical and hippocampal territories. It is proposed that the differential effects of cholinergic-rich transplants on different aspects of cognitive performance may define intrinsic limitations to the functional capacity of the ectopically placed grafts, which may be due to incomplete integration of the grafted cholinergic neurons into functional regulatory circuitries normally available to the basal forebrain cholinergic system.

Acetylcholinesterase↗

PubMed1996

Noradrenergic neurotransmission in the ventral spinal cord: basic characteristics and effects of denervating lesions, as studied in the awake rat by microdialysis.

Extracellular levels of noradrenaline (NA) were measured in the ventral horn of the lumbar spinal cord in awake unrestrained rats using in vivo microdialysis coupled to a highly sensitive radioenzymatic assay. In normal animals, baseline NA output averaged 13.4 +/- 2.2 fmol/30 microliters. KCl (100 mM) or desipramine (5 microM) added to the perfusion fluid increased NA levels 11.2-fold and 2.2-fold, respectively, whereas neuronal impulse blockade by tetrodotoxin (1 microM) added in the presence of desipramine stimulation produced a 88% reduction of extracellular NA levels. Noradrenergic denervation of the spinal cord by either electrolytic destruction of the noradrenaline-containing axon terminals or intraventricular 6-hydroxydopamine produced, 3-4 weeks later, dramatic 84 and 91% reductions in baseline NA release associated to a marked loss of immunoreactive noradrenergic fibers throughout the spinal cord or caudal to the site of electrolytic damage and almost completely abolished responses to pharmacological manipulations. The results support the view that spinal extracellular NA levels are neuronally derived, also suggesting that noradrenergic neurotransmission in the ventral spinal cord largely (by at least 85%) depends on the integrity of descending brainstem afferents. The microdialysis technique, thus, appears to be a useful tool for future studies on strategies aimed at promoting reinnervation and functional recovery in the deafferented spinal cord.

Adrenergic Uptake Inhibitors↗

PubMed1996

Extensive reinnervation of the hippocampus by embryonic basal forebrain cholinergic neurons grafted into the septum of neonatal rats with selective cholinergic lesions.

Reconstruction of the septohippocampal pathways by axons extending from embryonic cholinergic neuroblasts grafted into the neuron-depleted septum has been explored in the neonatal rat by using a novel lesioning and grafting protocol. Neonatal ablation of the basal forebrain cholinergic projection neurons, accompanied by extensive bilateral cholinergic denervation of the hippocampus and neocortex, was produced at postnatal day (PD) 4 by 192 immunoglobulin (IgG)-saporin intraventricularly. Four days later, cholinergic neuroblasts (from embryonic day 14 rats) were implanted bilaterally into the neuron-depleted septum by using a microtransplantation approach. The results show that homotopically implanted septal neurons survive and integrate well into the developing septal area, extending axons caudally along the myelinated fimbria-fornix and supracallosal pathways that are able to reach the appropriate targets in the denervated hippocampus and cingulate cortex as early as 4 weeks postgrafting. Moreover, the laminar innervation patterns established by the graft-derived axons closely resembled the normal ones and remained essentially unchanged up to at least 6 months, which was the longest postoperative time studied. The reinnervating fibers restored tissue choline acetyltransferase activity (up to 50% of normal) in the dorsal hippocampus and the parietooccipital cortex. Retrograde labeling with Fluoro-Gold from the host hippocampus combined with immunocytochemistry confirmed that most of the projecting neurons, indeed, were cholinergic. The results suggest that the graft-host interactions that are necessary for target-directed axon growth are present in the septohippocampal system during early postnatal maturation. Thus, the present approach may contribute to overcome the functional limitations inherent in the use of ectopically placed intrahippocampal transplants.

Acetylcholine↗

PubMed1996

Immunolesioning of basal forebrain cholinergic neurons facilitates hippocampal kindling and perturbs neurotrophin messenger RNA regulation.

The immunotoxin 192 IgG-saporin induces an efficient and specific lesion of low-affinity nerve growth factor receptor-bearing cholinergic neurons in the basal forebrain. Intraventricular injection of 192 IgG-saporin, which caused a complete loss of cholinergic afferents to the hippocampus and neocortex and a partial denervation of amygdala and piriform cortex, was found to markedly facilitate the initial stages of seizure development in hippocampal kindling. In contrast, the progression of kindling process from focal to generalized seizures was not affected. In situ hybridization demonstrated that basal levels of brain-derived neutrotrophic factor messenger RNA in the hippocampal formation and piriform cortex were significantly decreased by the lesion, which also attenuated the seizure-induced increase of brain-derived neurotrophic factor messenger RNA expression in the hippocampus and frontal cortex. In the dentate gyrus, the 192 IgG-saporin lesion selectively reduced the upregulation of messenger RNAs for brain-derived neurotrophic factor exons I and III after a generalized seizure, whereas the increase of exon II messenger RNA was unchanged. The lesion abolished the seizure-evoked increase of nerve growth factor and TrkC messenger RNA levels and decrease of neutrophin-3 messenger RNA expression in dentate granule cells, while TrkB messenger RNA levels were not affected. We conclude that the basal forebrain cholinergic system (1) suppresses kindling epileptogenesis in the hippocampus, and (2) enhances both basal and seizure-evoked brain-derived neurotrophic factor synthesis in the hippocampal formation and some cortical areas through a specific pattern of activation of promoters within the brain-derived neurotrophic factor gene.

Animals↗

PubMed1996

Effects of neonatal lesions of the basal forebrain cholinergic system by 192 immunoglobulin G-saporin: biochemical, behavioural and morphological characterization.

Selective removal of the basal forebrain cholinergic neurons by the immunotoxin 192 immunoglobulin G-saporin has offered a new powerful tool for the study of the relationships between cholinergic dysfunction and cognitive impairments. In the present study the morphological and functional consequences of selective lesions of the basal forebrain cholinergic system during early postnatal development have been investigated following bilateral intraventricular injections of 192 immunoglobulin G-saporin to immature (four-day-old) rats. Administration of increasing doses (0.2-0.8 microgram) of the immunotoxin produced dose-dependent loss of cholinergic neurons in the septal/diagonal band area (up to 72-86%) and in the nucleus basalis magnocellularis (up to 91-93%), paralleled by marked reductions in choline acetyltransferase activity in the hippocampus and several cortical regions (73-84%). The parvalbumin-positive neurons in the septal/diagonal band area and the calbindin-positive Purkinje cells in the cerebellum were unaffected at all dose levels. Brain dopamine or noradrenaline levels were unaffected or increased by the immunotoxin treatment. At the optimal dose, 0.4 microgram, the toxin conjugate produced maximal cholinergic depletion without significant mortality. Higher doses (0.8, 1.2 and 1.6 micrograms) of toxin, on the other hand, proved to be lethal for most or all of the injected animals. When tested at three and eight months after the optimal dose, in spite of persisting cholinergic depletion, the noenatally lesioned animals showed no impairment in the water maze task or in locomotor activity and exploration as compared to normal controls, probably reflecting partial sparing of the cholinergic neurons by the neonatal immunotoxic lesion (above all in the vertical and horizontal limbs of the diagonal band area), and/or a greater degree of plasticity in the developing as compared to the mature cholinergic system. The place navigational performance of the neonatally lesioned animals in the water maze task was abolished by central muscarinic cholinergic receptor blockade (by atropine) or by a second immunotoxic lesion, which eliminated virtually all residual cholinergic neurons in the septal/diagonal band area and the nucleus basalis. Administration of 192 immunoglobulin G-saporin to similarly trained, but previously normal adult rats, produced similar cholinergic depletions but much less severe place navigation deficits, suggesting that preoperative training on the task may reduce the functional consequences of a subsequent cholinergic lesion. The results thus support the view that the basal forebrain cholinergic system may be implicated in the acquisition rather than retention of spatial memory in the water maze task.

Animals↗

PubMed1996

Selective immunolesioning of the basal forebrain cholinergic system disrupts short-term memory in rats.

Selective depletion of nerve growth factor receptor-bearing neurons in the basal forebrain cholinergic system nuclei by the immunotoxin 192 IgG-saporin offers a new and highly useful tool for the study of the role of the forebrain cholinergic system in cognitive functions. In the present study, we have tested the effects of 192 IpG-saporin in an operant delayed matching-to-position task which has previously been used to discriminate between delay-dependent learning impairments and delay-independent disturbances of non-mnemonic processes. Rats were first trained to criterion performance and then received intraventricular injections of 5 microg of 192 IgG-saporin 4 weeks prior to a second testing session. Rats with 192 IgG-saporin lesions displayed a significant delay-dependent decline in performance compared to normal controls, indicating a deficit in short-term memory. Administration of the muscarinic blocker scopolamine (0.5 mg/kg, i.p.) produced more pronounced impairment in the performance of the normal control rats across all delays, and induced further impairment also in animals with 192 IgG-saporin lesions. These effects were not observed following control injections of methyl scopolamine, suggesting that the impairment induced by scopolamine was due to the blockade of central muscarinic receptors. No improvement in performance was observed in either group following systemic treatment with the muscarinic cholinergic agonist arecoline (1.00 mg/kg). Biochemical and morphological analyses confirmed the selective and severe (>90-95%) depletion of cholinergic neurons throughout the septal-diagonal band area and the nucleus basalis region by the intraventricular 192 IgG-saporin treatment. Although the immunotoxin was observed to produce additional damage to the cerebellar Purkinje cells, no gross motor abnormalities were observed that could contribute to the effects on accuracy in the task used here. In conclusion, the results show that selective combined lesions of the basal forebrain cholinergic neurons in the septal-diagonal band area and nucleus basalis produce long-lasting impairments in short-term memory, thus providing further support for a role of this system in cognitive functions.

Animals↗

PubMed1995

Branching serotonergic and non-serotonergic projections from caudal brainstem to the medial preoptic area and the lumbar spinal cord, in the rat.

The distribution and the chemical identity of retrogradely single and double labeled neurons in the caudal raphe nuclei were analyzed in the rat following injection of two fluorescent tracers into the medial preoptic area and the ventral/intermediate grey of the lumbar spinal cord, and serotonin immunocytochemistry. The results suggest that (1) neurons in the caudal raphe nuclei exhibit highly collateralized axons, able to simultaneously innervate rostrally- and caudally-located targets; (2) a large proportion (40-50%) of the raphe-spinal projection does not contain serotonin, which by contrast is present in more than 70% of the neurons projecting to the medial preoptic area; (3) only a small fraction of the observed collateralized projection is serotonergic. Thus, multiple transmitter systems are likely to be involved in the diffuse ascending and descending influence arising from these nuclei.

Animals↗

PubMed1995

Selective lesioning of the basal forebrain cholinergic system by intraventricular 192 IgG-saporin: behavioural, biochemical and stereological studies in the rat.

The elucidation of the functional role of the basal forebrain cholinergic system will require access to a highly specific and efficient cholinergic neurotoxin. Recently, selective depletion of the nerve growth factor (NGF) receptor-bearing cholinergic neurons in the rat basal forebrain and a dramatic loss of cholinergic innervation in the related cortical regions have been obtained following intraventricular injection of a newly introduced immunotoxin, 192 IgG-saporin. Here we extend these initial findings and report that administration of increasing doses (1.25, 2.5, 5.0 or 10 micrograms) of the 192 IgG-saporin conjugate into the lateral ventricles of adult rats induced dose-dependent impairments in the water maze task and passive avoidance retention, but only weak and inconsistent effects on locomotor activity. These behavioural changes were paralleled by a reduction in choline acetyltransferase activity in hippocampus and several cortical areas (up to 97%) and selective depletions of NGF receptor-positive cholinergic neurons in the septal-diagonal band area and nucleus basalis magnocellularis (up to 99%). By contrast, the non-cholinergic parvalbumin-containing neurons in the septum were completely spared, and other cholinergic projection systems (such as in the striatum, thalamus, brainstem and spinal cord) were unaffected even at the highest dose. The observed changes in the water maze and passive avoidance tasks, as well as the cholinergic cell loss, were maintained up to at least 8 months following the intraventricular injection of a single dose (5 micrograms) of the immunotoxin. The results confirm the usefulness of the 192 IgG-saporin toxin for selective and profound lesions of the basal forebrain cholinergic neurons and provide further support for a role of the basal forebrain cholinergic system in cognitive functions.

Acetylcholinesterase↗

PubMed1995

Activation of metabotropic glutamate receptors protects cultured neurons against apoptosis induced by beta-amyloid peptide.

Prolonged exposure of cultured cortical cells or cultured cerebellar granule cells to the residue 25-35 fragment of beta-amyloid peptide (beta AP), beta AP(25-35), induced neuronal apoptosis, as revealed by morphological analysis, fluorescent chromatin staining, and immunodetection of oligonucleosomes released from the nucleus into the cytoplasm. beta AP(25-35)-induced apoptosis was insensitive to ionotropic glutamate receptor antagonists but was substantially attenuated by the metabotropic glutamate receptor (mGluR) agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid. The neuroprotective action of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid was antagonized by (RS)-alpha-methyl-4-carboxyphenylglycine and was mimicked by (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (a selective agonist of mGluR2 and -3 subtypes) and by L-2-amino-4-phosphobutanoate and L-serine-O-phosphate (selective agonists of mGluR4, -6, and -7 subtypes). However, whereas all of these drugs behaved as neuroprotectants in cultured cortical cells, only L-2-amino-4-phosphobutanoate and L-serine-O-phosphate [and not (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine] reduced beta AP(25-35)-induced apoptosis in cultured cerebellar granule cells. The neuroprotective activity of mGluR agonists may be related to their ability to inhibit membrane Ca2+ conductance, because drugs that block voltage-sensitive Ca2+ channels, such as nimodipine or Co2+, could also attenuate beta AP(25-35)-induced apoptosis.

Aminobutyrates↗

PubMed1994

Inhibition of proopiomelanocortin expression by an oligodeoxynucleotide complementary to beta-endorphin mRNA.

Gene expression in mammalian cells can be suppressed by oligonucleotides complementary to the target mRNA. This strategy was explored as a means of arresting translation of the prohormone precursor proopiomelanocortin (POMC), used as a model system of peptide messengers that are synthesized and released from endocrine and neuronal cells. The synthesis of the POMC-derived peptides adrenocorticotropin (ACTH) and beta-endorphin (beta-END) was markedly reduced by an oligodeoxynucleotide (ODN) complementary to a region of beta-END mRNA in AtT-20 cells, which retain many of the differentiated phenotypes of corticotrophs; this treatment did not affect the steady-state levels of POMC mRNA. Antisense ODN was stable in cell culture medium for 24 h, and cellular uptake was low (approximately 2.5% of the added ODN); however, the intracellular levels of the ODN were sufficient to form a ribonuclease-resistant duplex with complementary cellular mRNA. Addition of ODN to the cell culture did not affect the cellular levels of chromogranin A-(264-314)/pancreastatin or cell viability and proliferation, as evidenced by bromodeoxyuridine incorporation and ornithine decarboxylase activity. Microinfusion of the antisense ODN in the rat hypothalamic arcuate nucleus, where the majority of POMC-positive brain perikarya are located, significantly reduced ACTH- and beta-END-immunopositive neurons, and antisense ODN-treated rats showed substantially less of the grooming behavior usually observed in a novel environment.

Animals↗

PubMed1994

Amphetamine induces excess release of striatal acetylcholine in vivo that is independent of nigrostriatal dopamine.

The effect of amphetamine on striatal acetylcholine (ACh) release was studied by an in vivo intrastriatal microdialysis technique. Although we expected systemic amphetamine to inhibit baseline striatal ACh release, the opposite was found. In addition, we found that the amphetamine-induced striatal ACh release did not depend on nigrostriatal DA since 6-hydroxydopamine (6-OHDA) lesions had no effect on amphetamine-induced ACh release. Local intrastriatal injection of amphetamine via the microdialysis probe had no effect on striatal ACh release even when the probe was located more laterally in striatum to take advantage of the medial to lateral gradient of striatal ACh and D2 receptors. The hypothesis that amphetamine increased extracellular striatal ACh by increasing the release of biogenic amines besides dopamine was tested by pharmacological manipulations designed to specifically increase local striatal norepinephrine or serotonin levels. The serotonergic and noradrenergic manipulations had no effect on striatal ACh levels. These results indicate that amphetamine-induced release of ACh in striatum is mediated via distal brain regions that are functionally connected with the striatum.

Acetylcholine↗