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O Lindvall

Publications and source records attributed to O Lindvall.

At least 127 records · Page 7Linked to original sources
PubMed1991

Host regulation of noradrenaline release from grafts of seizure-suppressant locus coeruleus neurons.

Intrahippocampal implants of noradrenaline-rich neural tissue from the fetal locus coeruleus region suppress development of seizures induced by hippocampal kindling stimulation in hyperexcitable, noradrenaline-depleted rats. In the present study the intracerebral microdialysis technique has been used to monitor seizure-induced release of noradrenaline from such grafts. The steady-state output of noradrenaline in the hippocampus of grafted animals (previously treated with intraventricular 6-hydroxydopamine) was similar to the baseline level in normal rats. A generalized seizure gave rise to a threefold increase of hippocampal noradrenaline levels as compared to baseline (15-min samples) in both normal and grafted animals. The maximal increase of extracellular noradrenaline levels occurred within 2-4 min after the onset of seizure activity and the levels then tapered off, reaching baseline after another 6-8 min. In 6-hydroxydopamine-treated animals without grafts baseline noradrenaline levels were markedly reduced compared to those of normal rats and only minor changes were observed in response to seizures. This supports the theory that the high extracellular noradrenaline concentrations measured in conjunction with seizures originate from the grafts. A knife cut transecting the ascending bundle from the locus coeruleus led to a marked attenuation of the seizure-induced increase of noradrenaline release in normal animals. In the intact brain, and probably also in the grafts, this response thus seems to be dependent on impulse flow in locus coeruleus neurons and only to a minor extent on local regulatory mechanisms in the hippocampus. In conclusion, the present study demonstrates that grafted locus coeruleus neurons are able to restore both basal and seizure-induced extracellular noradrenaline levels in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Prospects of transplantation in human neurodegenerative diseases.

Over the past decade experimental data obtained from animals have suggested that restoration or preservation of function through cell transplantation into the CNS might be developed into a useful therapeutic approach in human neurodegenerative disorders. Clinical trials in patients with Parkinson's disease have provided evidence that grafts of fetal dopaminergic neurons can survive and induce functional effects in the human brain, but no treatment based on transplantation is available yet. Initiation of studies of patients with striatal neural grafts in Huntington's disease is supported by findings in animal models, and is motivated by the lack of therapy and the severity of the symptoms in this disorder. Application of cell transplantation to other neurodegenerative disorders such as Alzheimer's disease, amyotrophic lateral sclerosis, and hereditary ataxia is definitely premature. Further progress can be made only by systematic studies in animals of the scientific issues that can now be defined, but will also require clinical trials in a few well-monitored patients.

Animals↗
PubMed1991

Increased levels of messenger RNAs for neurotrophic factors in the brain during kindling epileptogenesis.

Kindling, induced by repeated subconvulsive electrical or chemical stimulations leads to progressive and permanent amplification of seizure activity, culminating in generalized seizures. We report that kindling induced by electrical stimulation in the ventral hippocampus leads to a marked and transient increase in mRNA for NGF and BDNF in the dentate gyrus, the parietal cortex, and the piriform cortex. BDNF mRNA increased also in the pyramidal layer of hippocampus and in the amygdaloid complex. No change was seen in the level of HDNF/NT-3 mRNA. The increased expression of NGF and BDNF mRNAs was not influenced by pretreatment with the NMDA receptor antagonist MK801, but was partially blocked by the quisqualate, AMPA receptor antagonist NBQX. The presumed subsequent increase of the trophic factors themselves may be important for kindling-associated plasticity in specific neuronal systems in the hippocampus, which could promote hyperexcitability and contribute to the development of epileptic syndromes.

Animals↗
PubMed1991

Transplants in Parkinson's disease.

The objectives of this review are, first, to summarize results from clinical trials on patients with Parkinson's disease using grafts of either adrenal medulla or fetal substantia nigra and, second, to discuss some of the scientific issues that need to be clarified in more detail before transplantation can become a real therapeutic alternative in Parkinson's disease. Adrenal medulla autotransplantation using open microsurgery has been shown to effect a modest reduction of the duration and severity of off periods in about 30-50% of operated patients and to have a high morbidity and mortality rate. The mechanisms of improvement are unknown. It is concluded that adrenal medulla autotransplantation is an experimental approach and not a treatment for Parkinson's disease. Animal experimental data clearly favour the use of fetal dopamine (DA) neurons in patients, and clinical trials using such grafts are now going on in several countries. We have implanted human fetal mesencephalic tissue into the striatum in 6 patients. The findings indicate that fetal DA neurons can survive in the human parkinsonian brain and produce therapeutically valuable functional effects. Together with the solid animal experimental data the clinical observations support the idea that neural transplantation can be developed into an effective therapy in Parkinson's disease. However, it should be emphasized that such a treatment is presently not available and that further work is necessary to optimize the transplantation procedure, e.g. with respect to the yield of surviving DA neurons and the location and number of implantation sites to achieve the largest possible symptomatic improvement.

Adrenal Medulla↗
PubMed1990

Evidence for long-term reduction of noradrenaline release after kindling in the rat hippocampus.

The in vivo microdialysis technique was used to monitor steady-state noradrenaline release in the rat hippocampus after hippocampal kindling. At 8 weeks after the last seizure, the noradrenaline release was reduced by 62% in the stimulated hippocampus in kindled animals as compared to non-kindled rats. The reduction was not due to the repeated handling of the animals as assessed in a separate experiment. The results suggest a decrease of inhibitory noradrenergic influence at the primary kindling site, which could play a role in kindling epileptogenesis.

Animals↗
PubMed1990

Reformation of long axon pathways in adult rat central nervous system by human forebrain neuroblasts.

The failure of lesioned axons to regenerate over long distances in the mammalian central nervous system (CNS) is not due to an inability of central neurons to regenerate, but rather to the non-permissive nature of the CNS tissue environment. Regenerating CNS axons, which grow well within a peripheral nerve, for example, fail to penetrate mature CNS tissue by more than about 1 mm. Recent evidence indicates that this may be due to inhibitory membrane proteins associated with CNS oligodendrocytes and myelin. We report here that human telencephalic neuroblasts implanted into the excitotoxically lesioned striatum of adult rats can escape or neutralize this inhibitory influence of the adult CNS environment and extend axons along major myelinated fibre tracts for distances of up to approximately 20 mm. The axons were seen to elongate along the paths of the striato-nigral and cortico-spinal tracts to reach the substantia nigra, the pontine nuclei and the cervical spinal cord, which are the normal targets for the striatal and cortical projection neurons likely to be present in these implants.

Animals↗
PubMed1990

Grafts of fetal dopamine neurons survive and improve motor function in Parkinson's disease.

Neural transplantation can restore striatal dopaminergic neurotransmission in animal models of Parkinson's disease. It has now been shown that mesencephalic dopamine neurons, obtained from human fetuses of 8 to 9 weeks gestational age, can survive in the human brain and produce marked and sustained symptomatic relief in a patient severely affected with idiopathic Parkinson's disease. The grafts, which were implanted unilaterally into the putamen by stereotactic surgery, restored dopamine synthesis and storage in the grafted area, as assessed by positron emission tomography with 6-L-[18F]fluorodopa. This neurochemical change was accompanied by a therapeutically significant reduction in the patient's severe rigidity and bradykinesia and a marked diminuation of the fluctuations in the patient's condition during optimum medication (the "on-off" phenomenon). The clinical improvement was most marked on the side contralateral to the transplant.

Brain↗
PubMed1990

Seizure suppression in kindling epilepsy by intrahippocampal locus coeruleus grafts: evidence for an alpha-2-adrenoreceptor mediated mechanism.

Intrahippocampal cell suspension grafts, prepared from the locus coeruleus region of rat fetuses, have previously been shown to retard seizure development in rats made hypersensitive to hippocampal kindling by a lesion of the forebrain noradrenergic system. The objective of the present study was to provide evidence that the seizure-suppressant effect elicited by the grafts is mediated via noradrenergic mechanisms. Two groups of rats received 6-hydroxydopamine in the lateral ventricle and then bilateral intrahippocampal locus coeruleus grafts. After 3 months, the grafted animals and a group of normal rats were subjected to hippocampal kindling. One group of grafted animals and the normal rats were injected intraperitoneally with the alpha-2 adrenergic receptor blocker idazoxan before each kindling stimulation. The other grafted rats received vehicle injections. The development of seizures was significantly faster in the grafted and normal rats that had been given idazoxan than in the grafted rats that had not been subjected to alpha-2 receptor blockade. Our data suggest that the seizure-suppressant action exerted by grafts of fetal locus coeruleus in hippocampal kindling is mediated via noradrenergic mechanisms, most likely via activation of postsynaptic alpha-2 adrenoreceptors.

Adrenergic beta-Antagonists↗
PubMed1990

Neuronal damage in the striatum following forebrain ischemia: lack of effect of selective lesions of mesostriatal dopamine neurons.

Transient periods of global cerebral ischemia lead to selective neuronal damage in the striatum. We investigated the effects of unilateral 6-hydroxydopamine lesions of the mesostriatal dopamine (DA) system on the density and distribution of neuronal necrosis in the rat striatum following ischemia induced by bilateral occlusion of the common carotid arteries combined with hypotension. After both 12 and 15 min of ischemia, which caused slight and extensive striatal damage, respectively, there was no difference in the density of neuronal necrosis in the striatum between DA-lesioned and sham-operated animals. We conclude that the DA system alone does not modulate injury following complete cerebral ischemia, but may contribute significantly to damage following conditions such as during hypoglycemia and incomplete cerebral ischemia.

Animals↗
PubMed1990

Formation of synaptic graft-host connections by noradrenergic locus coeruleus neurons transplanted into the adult rat hippocampus.

Transplants of cell suspension obtained from the locus coeruleus region of 13- to 14-day-old rat fetuses were implanted into the hippocampal formation of intact adult rats or rats from which the noradrenergic afferents to the hippocampus had been removed by bilateral 6-hydroxydopamine (6-OHDA) injections into the dorsal tegmental noradrenergic bundle. The growth noradrenergic axons into the host hippocampus from the implant was studied at 4-8 months after surgery by immunohistochemistry using antisera raised against tyrosine hydroxylase or noradrenaline. In the animals with an intact noradrenergic system the host noradrenergic afferents were removed by bilateral dorsal bundle lesions 2 weeks before sacrifice. Fine axon-like fibers (diameter about 0.3 micron) and thick dendrite-like fibers (diameter about 1.3 micron), labeled immunohistochemically, were abundant and spread far from the graft. By electron microscopy, immunolabeled axon-like fibers formed mostly symmetrical synaptic contacts with nonlabeled spines and shafts of dendrites in the host. Labeled dendrite-like fibers of presumed graft origin penetrated deep into the host neuropil and received abundant afferents from nonlabeled axon terminals. The extent of graft-derived noradrenergic axons and the synapses established with the host hippocampal neurons were similar in the chronically denervated animals and in the animals where the intrinsic noradrenergic afferents had been left intact until 2 weeks before sacrifice. The results show that implanted embryonic noradrenergic neurons are able to innervate the hippocampus in both the presence and the absence of an intact intrinsic noradrenergic innervation and that the ingrowing axons form abundant synaptic connections with the host hippocampal neurons under both conditions. Dendritic processes from the grafted noradrenergic neurons that extend deep into the host tissue may receive a reciprocal synaptic host afferent input.

Animals↗
PubMed1990

Intracerebral microdialysis as a tool to monitor transmitter release from grafted cholinergic and monoaminergic neurons.

In the present study the microdialysis technique has been used as a tool for the study of functional regulation of intracerebrally grafted cholinergic and monoaminergic neurons as well as for the analysis of graft-host interactions. Fetal noradrenergic, serotonergic, dopaminergic, and cholinergic neurons were transplanted into the hippocampus or striatum previously denervated of their intrinsic monoaminergic or cholinergic afferents. After a few months survival, when the grafts had reinnervated the surrounding target, dialysis probes were implanted into the graft-reinnervated region. Although the graft-derived fiber and terminal density varied substantially from one animal to another the transmitters in the extracellular space were maintained at near-normal levels, not only under baseline conditions, but also during K(+)-induced depolarization, transmitter-selective uptake blockade, and tetrodotoxin. This suggests that the grafted neurons possess efficient autoregulatory properties despite their ectopic location. The results also show that monoamine release in the graft-reinnervated host target is impulse-dependent, and that the neurons are spontaneously functionally active at the synaptic level. Electrical stimulation of the lateral habenula (which has previously been identified as a powerful activator of the intrinsic hippocampal cholinergic and noradrenergic afferents) produced a similar increase in the release of these transmitters in the intact and grafted hippocampi. A complex environmental stimulus, such as handling, induced a consistent increase in acetylcholine but not noradrenaline release in the hippocampus. These findings suggest that grafted cholinergic and noradrenergic neurons can be functionally activated by host brain inputs.

Animals↗