neuropeptide-y and Nerve-Degeneration

The high prevalence of osteoporosis, observed in multiple sclerosis (MS) patients, has been attributed to reduced mobility and or the use of disease-modifying drugs. However, MS-impaired cardiovascular autonomic nervous system (ANS) function has the potential of reducing bone mass density (BMD) by altering the expression and/or function of the neuronal, systemic, and local mediators of bone remodeling. This review describes the complex regulation of bone homeostasis with a focus on MS, providing evidence that ANS dysfunction and low BMD are intertwined with MS inflammatory and neurodegenerative processes, and with other MS-related morbidities, including depression, fatigue, and migraine. Strategies for improving ANS function could reduce the prevalence of MS osteoporosis and slow the rate of MS progression, with a significant positive impact on patients' quality of life.

Topics: Adiponectin; Autonomic Nervous System; Bone Density; Bone Remodeling; Brain; Cardiovascular System; Depression; Endocannabinoids; Fatigue; Humans; Inflammation; Leptin; Migraine Disorders; Multiple Sclerosis; Nerve Degeneration; Neuropeptide Y; Osteocalcin; Osteopontin; Osteoporosis; Osteoprotegerin; Parathyroid Hormone; RANK Ligand; Serotonin; Vitamin D

Topics: Animals; Dentate Gyrus; Disease Models, Animal; Epilepsy; Epilepsy, Temporal Lobe; gamma-Aminobutyric Acid; Hippocampus; Humans; Mossy Fibers, Hippocampal; Nerve Degeneration; Neuronal Plasticity; Neuropeptide Y; Rats; Receptors, GABA-A; Status Epilepticus; Synaptic Transmission

NPY-neurons in the striatum and cortex have many morphological and chemical features in common. They are intrinsic, medium sized, aspiny and exhibit ultrastructural characteristics typical of neurons undergoing active synthesis and release of peptides. Most of the NPY-neurons in the two regions coexist with somatostatin, exhibit high levels of NADPH-diaphorase and are resistant to degeneration associated with Huntington's disease. Ultrastructural analysis suggests that the ensheathment by glia and sparsity of asymmetric (putatively excitatory) inputs may render NPY neurons resistant to excitotoxicity. Although NPY-neurons receive few inputs, they make numerous contacts with dendrites within a small region of the neuropil. Among their targets are GABAergic neurons. These NPY-receptive GABA neurons differ from other GABAergic neurons in the vicinity in that they receive few other inputs along their somata and proximal dendrites. This suggests that NPY may exert more influence on a specific class of GABAergic neurons. Many more of the NPY-terminals are found at sites that would be strategic for the simultaneous modulation of the release of transmitters and postsynaptic responses. The differences among NPY-neurons in the striatum versus cerebral cortex are mainly chemical. Most notably, the NPY-neurons are GABAergic in the cortex and not GABAergic in the striatum. In addition, some of the NPY-axons in the ventral portions of striatum and cerebral cortex may be catecholaminergic, and thus originate in brainstem areas recognized to contain NPY and epinephrine or norepinephrine. NPY- and catecholaminergic fibers converge onto same dendrites. Thus, the two transmitters may interact through intercellular biochemical pathways postsynaptically. Finally, the sites where the two fibers directly contact each other may be where NPY stimulates the turnover of dopamine.

Topics: Animals; Blood Vessels; Brain Mapping; Catecholamines; Cats; Cerebral Cortex; Corpus Striatum; gamma-Aminobutyric Acid; Microscopy, Electron; Nerve Degeneration; Neurons; Neuropeptide Y; Rats; Synaptic Transmission

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons in the nigro-striatal pathway. Interestingly, it has already been shown that an intracerebral administration of neuropeptide Y (NPY) decreases the neurodegeneration induced by 6-hydroxydopamine (6-OHDA) in rodents and prevents loss of dopamine (DA) and DA transporter density. The etiology of idiopathic PD now suggest that chronic production of inflammatory mediators by activated microglial cells mediates the majority of DA-neuronal tissue destruction. In an animal experimental model of PD, the present study shows that NPY inhibited the activation of microglia evaluated by the binding of the translocator protein (TSPO) ligand [3H]PK11195 in striatum and substantia nigra of 6-OHDA rats. These results suggest a potential role for inflammation in the pathophysiology of the disease and a potential treatment by NPY in PD.

Topics: Animals; Corpus Striatum; Disease Models, Animal; Dopamine; Dopamine Plasma Membrane Transport Proteins; Dopaminergic Neurons; Inflammation; Male; Microglia; Nerve Degeneration; Neuropeptide Y; Neuroprotection; Oxidopamine; Parkinson Disease; Rats; Rats, Wistar; Substantia Nigra

Antiepileptic drug therapy, though beneficial for restraining seizures, cannot thwart status epilepticus (SE) induced neurodegeneration or down-stream detrimental changes. We investigated the efficacy of resveratrol (RESV) for preventing SE-induced neurodegeneration, abnormal neurogenesis, oxidative stress and inflammation in the hippocampus. We induced SE in young rats and treated with either vehicle or RESV, commencing an hour after SE induction and continuing every hour for three-hours on SE day and twice daily thereafter for 3 days. Seizures were terminated in both groups two-hours after SE with a diazepam injection. In contrast to the vehicle-treated group, the hippocampus of animals receiving RESV during and after SE presented no loss of glutamatergic neurons in hippocampal cell layers, diminished loss of inhibitory interneurons expressing parvalbumin, somatostatin and neuropeptide Y in the dentate gyrus, reduced aberrant neurogenesis with preservation of reelin + interneurons, lowered concentration of oxidative stress byproduct malondialdehyde and pro-inflammatory cytokine tumor necrosis factor-alpha, normalized expression of oxidative stress responsive genes and diminished numbers of activated microglia. Thus, 4 days of RESV treatment after SE is efficacious for thwarting glutamatergic neuron degeneration, alleviating interneuron loss and abnormal neurogenesis, and suppressing oxidative stress and inflammation. These results have implications for restraining SE-induced chronic temporal lobe epilepsy.

Topics: Animals; Behavior, Animal; Cell Adhesion Molecules, Neuronal; Cell Death; Cognition; Extracellular Matrix Proteins; GABAergic Neurons; Gene Expression Regulation; Hippocampus; Inflammation; Interneurons; Longevity; Male; Microglia; Nerve Degeneration; Nerve Tissue Proteins; Neurogenesis; Neuropeptide Y; Oxidative Stress; Parvalbumins; Rats, Inbred F344; Reelin Protein; Resveratrol; Seizures; Serine Endopeptidases; Somatostatin; Status Epilepticus; Stilbenes; Tumor Necrosis Factor-alpha

The effects of intracerebroventricular administration of neuropeptide Y (NPY), which is believed to play an important role in neuroprotection against excitotoxicity and in the modulation of adult neurogenesis, were evaluated in an animal model of hippocampal neurodegeneration and temporal lobe epilepsy represented by trimethyltin (TMT) intoxication. A single TMT injection (8 mg/kg) causes, in the rat brain, massive neuronal death, selectively involving pyramidal neurons, accompanied by glial activation and enhanced hippocampal neurogenesis. Our data indicate that intracerebroventricular administration of exogenous NPY (at the dose of 2 μg/2 μL, 4 days after TMT-administration), in adult rats, exerts a protective role in regard to TMT-induced hippocampal damage and a proliferative effect on the hippocampal neurogenic niche through the up-regulation of Bcl-2, Bcl2l1, Bdnf, Sox-2, NeuroD1, Noggin and Doublecortin genes, contributing to delineate more clearly the role of NPY in in vivo neurodegenerative processes.

Topics: Animals; Antimetabolites; Apoptosis Regulatory Proteins; Brain-Derived Neurotrophic Factor; Bromodeoxyuridine; Doublecortin Protein; Epilepsy, Temporal Lobe; Female; Gene Expression; Hippocampus; Immunohistochemistry; Injections, Intraventricular; Nerve Degeneration; Nerve Tissue Proteins; Neurogenesis; Neuropeptide Y; Neuroprotective Agents; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Receptors, Neuropeptide Y; RNA; Trimethyltin Compounds

In this study, we performed immunohistochemistry for somatostatin (SS), neuropeptide Y (NPY), and parvalbumin (PV) in LiCl-pilocarpine-treated rats to observe quantitative changes and axonal sprouting of GABAergic interneurons in the hippocampus, especially in the sclerotic hippocampus. Fluoro-Jade B (FJB) was performed to detect the specific degeneration of GABAergic interneurons. Compared with age-matched control rats, there were fewer SS/NPY/PV-immunoreactive (IR) interneurons in the hilus of the sclerotic hippocampus in pilocarpine-treated rats; hilar dentritic inhibitory interneurons were most vulnerable. FJB stain revealed degeneration was evident at 2 months after status epilepticus. Some SS-IR and NPY-IR interneurons were also stained for FJB, but there was no evidence of degeneration of PV-IR interneurons. Axonal sprouting of GABAergic interneurons was present in the hippocampus of epileptic rats, and a dramatic increase of SS-IR fibers was observed throughout all layers of CA1 region in the sclerotic hippocampus. These results confirm selective loss and degeneration of a specific subset of GABAergic interneurons in specific subfields of the hippocampus. Axonal sprouting of inhibitory GABAergic interneurons, especially numerous increase of SS-IR neutrophils within CA1 region of the sclerotic hippocampus, may constitute the aberrant inhibitory circum and play a significant role in the generation and compensation of temporal lobe epilepsy.

Topics: Animals; Axons; Disease Models, Animal; gamma-Aminobutyric Acid; Hippocampus; Interneurons; Lithium Chloride; Male; Nerve Degeneration; Neuropeptide Y; Parvalbumins; Pilocarpine; Rats; Rats, Sprague-Dawley; Sclerosis; Somatostatin; Status Epilepticus

The endopeptidase neprilysin (NEP) is a major amyloid-beta (Abeta) degrading enzyme and has been implicated in the pathogenesis of Alzheimer's disease. Because NEP cleaves substrates other than Abeta, we investigated the potential role of NEP-mediated processing of neuropeptides in the mechanisms of neuroprotection in vivo. Overexpression of NEP at low levels in transgenic (tg) mice affected primarily the levels of neuropeptide Y (NPY) compared with other neuropeptides. Ex vivo and in vivo studies in tg mice and in mice that received lentiviral vector injections showed that NEP cleaved NPY into C-terminal fragments (CTFs), whereas silencing NEP reduced NPY processing. Immunoblot and mass spectrometry analysis showed that NPY 21-36 and 31-36 were the most abundant fragments generated by NEP activity in vivo. Infusion of these NPY CTFs into the brains of APP (amyloid precursor protein) tg mice ameliorated the neurodegenerative pathology in this model. Moreover, the amidated NPY CTFs protected human neuronal cultures from the neurotoxic effects of Abeta. This study supports the possibility that the NPY CTFs generated during NEP-mediated proteolysis might exert neuroprotective effects in vivo. This function of NEP represents a unique example of a proteolytic enzyme with dual action, namely, degradation of Abeta as well as processing of NPY.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Arginine; Benzazepines; Cells, Cultured; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation; Genetic Vectors; Humans; Mice; Mice, Transgenic; Neprilysin; Nerve Degeneration; Nerve Growth Factors; Neurons; Neuropeptide Y; Peptide Fragments; Receptors, Neuropeptide Y

Calorie restriction (CR), which is thought to be largely dependent on the neuroendocrine system modulated by insulin/insulin-like growth factor-I (IGF-I) and leptin signaling, decreases morbidity and increases lifespan in many organisms. To elucidate whether insulin and leptin sensitivities are indispensable in the metabolic adaptation to CR, we investigated the effects of CR on obese Zucker (fa/fa) rats and lean control (+/+) rats. CR did not fully improve insulin resistance in (fa/fa) rats. Nonetheless, CR induced neuropeptide Y (NPY) expression in the hypothalamic arcuate nucleus and metabolism related gene expression changes in the liver in (fa/fa) rats and (+/+) rats. Up-regulation of NPY augmented plasma corticosterone levels and suppressed pituitary growth hormone (GH) expression, thereby modulating adipocytokine production to induce tissue-specific insulin sensitivity. Thus, central NPY activation via peripheral signaling might play a crucial role in the effects of CR, even in insulin resistant and leptin receptor deficient conditions.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Caloric Restriction; Gene Expression Regulation; Ghrelin; Gluconeogenesis; Growth Hormone; Hepatocyte Nuclear Factor 4; Insulin; Leptin; Liver; Mitochondria; Nerve Degeneration; Neuropeptide Y; Obesity; Oxidation-Reduction; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Pituitary Gland; Protein Binding; Rats; Rats, Zucker; Receptors, Leptin; RNA-Binding Proteins; Thinness; Transcription Factors

Urokinase-type plasminogen activator receptor (uPAR) is functionally a pleiotropic mediator involved in cell adhesion, proliferation, differentiation and migration as well as in matrix degradation, apoptosis, and angiogenesis in cancer tissue. Comparable cellular alterations occur in the brain during post-injury tissue repair. As the first step to assess the role of uPAR in brain tissue remodeling, we tested a hypothesis that uPAR expression is altered in the hippocampus during epilepsy-related circuitry reorganization. Epileptogenesis was triggered by inducing status epilepticus (SE) with electrical stimulation of the amygdala in rats. To monitor the development of SE and the occurrence of spontaneous seizures animals were continuously video-EEG monitored until sacrificed (1, 2, 4 or 14 days after SE). The hippocampal expression of uPAR was studied with real time qPCR and immunohistochemistry. Double-immunohistochemistry and confocal microscopy were used to investigate the expression of uPAR in astrocytes, microglia and neurons. We show that in the normal hippocampus the expression of uPAR was low and confined to small population of astrocytes and interneurons. In animals undergoing SE, uPAR expression increased dramatically, peaking at 1 and 4 days after SE. According to double-immunohistochemistry, uPAR was highly expressed in parvalbumin positive interneurons in the hippocampus and dentate gyrus, and in a subgroup of somatostatin and neuropeptide Y positive hilar interneurons. Increased uPAR expression during post-injury phase supports its contribution to tissue remodeling in the brain. Surviving hilar interneurons that are known to be denervated due to loss of afferent inputs in post-SE brain provide a target for future studies to investigate the contribution of uPAR in reinnervation of these cells, and to identify the signaling cascades that mediate the effects of uPAR.

Topics: Animals; Astrocytes; Cell Line; Disease Models, Animal; Electric Stimulation; Epilepsy; Gene Expression Regulation; Hippocampus; Humans; Immunohistochemistry; Interneurons; Kindling, Neurologic; Male; Nerve Degeneration; Neuropeptide Y; Parvalbumins; Rats; Rats, Sprague-Dawley; Receptors, Urokinase Plasminogen Activator; RNA, Messenger; Signal Transduction; Somatostatin; Up-Regulation

Agouti-related protein (AgRP) is a key orexigenic neuropeptide expressed in the hypothalamic arcuate nucleus and a marker for neurons conveying hormonal signals of hunger to the brain. Mice homozygous for the anorexia (anx) mutation are characterized by decreased food intake, starvation, and death by 3-5 weeks of age. At this stage immunoreactivity for AgRP is increased in cell bodies but decreased in the nerve terminals. We studied when during early postnatal development the aberrant phenotype of the AgRP system becomes apparent in anx/anx mice and possible underlying mechanisms. AgRP and ionized calcium binding adapter molecule (Iba1), a marker for activated microglia, as well as Toll-like receptor 2 (TLR-2), were studied by immunohistochemistry at postnatal days P1, P5, P10, P12, P15 and P21 in anx/anx and wild-type mice. We found that the AgRP system in the anx/anx mouse develops similarly to the wild type until P12, when AgRP fibers in anx/anx mice cease to increase in density in the main projection areas. At P21, AgRP fiber density in anx/anx mice was significantly reduced vs. P15, in certain regions. At P21, many strongly AgRP-positive cell bodies were observed in the anx/anx arcuate nucleus vs. only few and weakly fluorescent ones in the wild type. The decrease in AgRP fiber density in anx/anx mice overlapped with an increase in Iba1 and TLR-2 immunoreactivities. Thus, the aberrant appearance of the AgRP system in the anx/anx mouse in the early postnatal development could involve a microglia-associated process and the innate immune system.

Topics: Agouti-Related Protein; Animals; Anorexia; Antibodies; Arcuate Nucleus of Hypothalamus; Calcium-Binding Proteins; Eating; Female; Immunohistochemistry; Male; Mice; Mice, Inbred Strains; Mice, Mutant Strains; Microfilament Proteins; Microglia; Mutation; Nerve Degeneration; Neuropeptide Y; Toll-Like Receptor 2

This study characterized morphological changes in the cortex and hippocampus of Sprague-Dawley rats following photothrombotic infarction and epileptogenesis with emphasis on the distribution of neuropeptide Y (NPY) expression. Animals were lesioned in the left sensorimotor cortex and compared with age-matched naive and sham-operated controls by immunohistochemical techniques at 1, 3, 7, and 180 days post-lesioning (DPL). NPY immunostaining was assessed by light microscopy and quantified by the optical fractionator technique using unbiased stereological methods. At 1, 3, and 7 DPL, the number of NPY-positive somata in the lesioned cortex was increased significantly compared to controls and the contralateral cortex. At 180 DPL, lesioned epileptic animals with frequent seizure activity demonstrated significant increases of NPY expression in the cortex, CA1, CA3, hilar interneurons, and granule cells of the dentate gyrus. In addition to NPY immunostaining, neuronal degeneration, cell death/cell loss, and astroglial response were assessed with cell-specific markers. Nissl and NeuN staining showed reproducible infarctions at each investigated time point. FJB-positive somata were most abundant in the infarct core at 1 DPL, decreased markedly at 3 DPL, and virtually absent by 7 DPL. Activated astroglia were detected in the cortex and hippocampus following lesioning and the development of seizure activity. In summary, NPY protein expression and morphological changes following cortical photothrombosis were time-, region-, and pathologic state-dependent. Alterations in NPY expression may reflect reactive or compensatory responses of the rat brain to acute infarction and to the development and expression of epileptic seizures.

Topics: Animals; Astrocytes; Brain; Brain Infarction; Dentate Gyrus; Disease Models, Animal; DNA-Binding Proteins; Epilepsy; Fluoresceins; Gliosis; Hippocampus; Immunohistochemistry; Intracranial Thrombosis; Light Coagulation; Nerve Degeneration; Nerve Tissue Proteins; Neurons; Neuropeptide Y; Nuclear Proteins; Organic Chemicals; Rats; Rats, Sprague-Dawley; Somatosensory Cortex; Time Factors; Up-Regulation

Neuropeptide-containing hippocampal interneurons and dentate granule cell inhibition were investigated at different periods following electrical stimulation-induced, self-sustaining status epilepticus (SE) in rats. Immunohistochemistry for somatostatin (SOM), neuropeptide Y (NPY), parvalbumin (PV), cholecystokinin (CCK), and Fluoro-Jade B was performed on sections from hippocampus contralateral to the stimulated side and studied by confocal laser scanning microscopy. Compared to paired age-matched control animals, there were fewer SOM and NPY-immunoreactive (IR) interneurons in the hilus of the dentate gyrus in animals with epilepsy (40-60 days after SE), and 1, 3, and 7 days following SE. In the hilus of animals that had recently undergone SE, some SOM-IR and NPY-IR interneurons also stained for Fluoro-Jade B. Furthermore, there was electron microscopic evidence of the degeneration of SOM-IR interneurons following SE. In contrast, the number of CCK and PV-IR basket cells in epileptic animals was similar to that in controls, although it was transiently diminished following SE; there was no evidence of degeneration of CCK or PV-IR interneurons. Patch-clamp recordings revealed a diminished frequency of inhibitory postsynaptic currents in dentate granule cells (DGCs) recorded from epileptic animals and animals that had recently undergone SE compared with controls. These results confirm the selective vulnerability of a particular subset of dentate hilar interneurons after prolonged SE. This loss may contribute to the reduced GABAergic synaptic inhibition of granule cells in epileptic animals.

Topics: Animals; Cholecystokinin; Dentate Gyrus; Electric Stimulation; Epilepsy, Temporal Lobe; Fluorescent Dyes; Inhibitory Postsynaptic Potentials; Interneurons; Male; Matched-Pair Analysis; Nerve Degeneration; Neuropeptide Y; Parvalbumins; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Somatostatin; Synaptic Transmission

Major aspects of temporal lobe epilepsy (TLE) can be reproduced in mice following a unilateral injection of kainic acid into the dorsal hippocampus. This treatment induces a non-convulsive status epilepticus and acute lesion of CA1, CA3c and hilar neurons, followed by a latent phase with ongoing ipsilateral neuronal degeneration. Spontaneous focal seizures mark the onset of the chronic phase. In striking contrast, the ventral hippocampus and the contralateral side remain structurally unaffected and seizure-free. In this study, functional and neurochemical alterations of the contralateral side were studied to find candidate mechanisms underlying the lack of a mirror focus in this model of TLE. A quantitative analysis of simultaneous, bilateral EEG recordings revealed a significant decrease of theta oscillations ipsilaterally during the latent phase and bilaterally during the chronic phase. Furthermore, the synchronization of bilateral activity, which is very high in control, was strongly reduced already during the latent phase and the decrease was independent of recurrent seizures. Immunohistochemical analysis performed in the contralateral hippocampus of kainate-treated mice revealed reduced calbindin-labeling of CA1 pyramidal cells; down-regulation of CCK-8 and up-regulation of NPY-labeling in mossy fibers; and a redistribution of galanin immunoreactivity. These changes collectively might limit neuronal excitability in CA1 and dentate gyrus, as well as glutamate release from mossy fiber terminals. Although these functional and neurochemical alterations might not be causally related, they likely reflect long-ranging network alterations underlying the independent evolution of the two hippocampal formations during the development of an epileptic focus in this model of TLE.

Topics: Action Potentials; Animals; Brain Chemistry; Calbindins; Chronic Disease; Disease Models, Animal; Down-Regulation; Electroencephalography; Epilepsy; Epilepsy, Temporal Lobe; Functional Laterality; Galanin; Hippocampus; Kainic Acid; Mice; Mossy Fibers, Hippocampal; Nerve Degeneration; Neural Pathways; Neuropeptide Y; Neurotoxins; Pyramidal Cells; S100 Calcium Binding Protein G; Sincalide; Status Epilepticus; Theta Rhythm; Up-Regulation

Mossy fiber sprouting (MFS), a common feature of human temporal lobe epilepsy and many epilepsy animal models, contributes to hippocampal hyperexcitability. The molecular events responsible for MFS are not well understood, although the growth-associated protein GAP-43 has been implicated in rats. Here, we focus on the hyaluronan receptor CD44, which is involved in routing of retinal axons during development and is upregulated after injury in many tissues including brain. After pilocarpine-induced status epilepticus (SE) in mice most hilar neurons died and neuropeptide Y (NPY) immunoreactivity appeared in the dentate inner molecular layer (IML) after 10-31 days indicative of MFS. Strong CD44 immunoreactivity appeared in the IML 3 days after pilocarpine, then declined over the next 4 weeks. Conversely, GAP-43 immunoreactivity was decreased in the IML at 3-10 days after pilocarpine-induced SE. After SE induced by repeated kainate injections, mice did not show any hilar cell loss or changes in CD44 or GAP-43 expression in the IML, and MFS was absent at 20-35 days. Thus, after SE in mice, early loss of GAP-43 and strong CD44 induction in the IML correlated with hilar cell loss and subsequent MFS. CD44 is one of the earliest proteins upregulated in the IML and coincides with early sprouting of mossy fibers, although its function is still unknown. We hypothesize that CD44 is involved in the response to axon terminal degeneration and/or neuronal reorganization preceding MFS.

Topics: Animals; Dentate Gyrus; Disease Models, Animal; Epilepsy, Temporal Lobe; GAP-43 Protein; Growth Cones; Hyaluronan Receptors; Immunohistochemistry; Kainic Acid; Mice; Mossy Fibers, Hippocampal; Nerve Degeneration; Neuronal Plasticity; Neuropeptide Y; Pilocarpine; Status Epilepticus; Up-Regulation

Brain derived neurotrophic factor (BDNF) has been suggested to be involved in epileptogenesis. Both pro- and antiepileptogenic effects have been reported, but the exact physiological role is still unclear. Here, we investigated the role of endogenous BDNF in epileptogenesis by using transgenic mice overexpressing truncated trkB, a dominant negative receptor of BDNF. After induction of status epilepticus (SE) by kainic acid, the development of spontaneous seizures was monitored by video-EEG system. Hilar cell loss, and the number of neuropeptide Y immunoreactive cells were studied as markers of cellular damage, and mossy fibre sprouting was investigated as a plasticity marker. Our results show that transgenic mice had significantly less frequent interictal spiking than wild-type mice, and the frequency of spontaneous seizures was lower. Furthermore, compared to wild-type animals, transgenic mice had less severe seizures with later onset and mortality was lower. In contrast, no differences between genotypes were observed in any of the cellular or plasticity markers. Our results suggest that transgenic mice with decreased BDNF signalling have reduced epileptogenesis.

Topics: Action Potentials; Animals; Brain-Derived Neurotrophic Factor; Dentate Gyrus; Down-Regulation; Epilepsy; Epilepsy, Temporal Lobe; Excitatory Amino Acid Agonists; Female; Growth Cones; Male; Mice; Mice, Transgenic; Mossy Fibers, Hippocampal; Nerve Degeneration; Neuronal Plasticity; Neuropeptide Y; Receptor, trkB; Signal Transduction

Prior epileptic episodes have been shown to decrease markedly the neuronal damage induced by a second epileptic episode, similar to the tolerance following an episode of mild ischemia. Endogenous neuroprotective effects mediated by various mechanisms have been put forward. This study investigated whether neuroprotection against the excitotoxic damage induced by re-exposure to an epileptic challenge can reflect a change in epileptic susceptibility. Tolerance was elicited in rats by a preconditioning session using intrahippocampal kainic acid (KA) administration followed at 1, 7 and 15-day intervals by a subsequent intraventricular KA injection. The degree of pyramidal cell loss in the vulnerable CA3 subfield contralateral to the KA-injected hippocampus was extensively reduced in animals experiencing KA ventricular administration. This neuroprotection was highly significant 1 and 7 days after injection, but not 15 days after injection. In preconditioned animals, the after-discharge threshold was assessed as an index of epileptic susceptibility. It increased significantly from 1 to 15 days after intrahippocampal KA administration. Finally, an enhancement of neuropeptide Y expression in both non-principal cells and mossy fibers was detected, occurring at the same time as the decrease in epileptic susceptibility. These results provide further evidence of an 'epileptic tolerance' as shown by the substantial neuroprotective effect of a prior episode of epileptic activity upon subsequent epileptic insult and suggest that the prevention of excitotoxic damage after preconditioning results from an endogenous neuroprotective mechanism against hyperexcitability and seizures.

Topics: Adaptation, Physiological; Animals; Behavior, Animal; Cell Death; Disease Models, Animal; Disease Susceptibility; Epilepsy; Excitatory Amino Acid Agonists; Hippocampus; Immunohistochemistry; Kainic Acid; Male; Nerve Degeneration; Neuropeptide Y; Neurotoxins; Pyramidal Cells; Rats; Rats, Wistar

In this study we have used fluorescent microspheres to retrogradely label primary sensory neurons in dorsal root ganglia (DRGs). Following injection into peripheral nerves, the animals were allowed to survive up to 480 days. Simple profile count indicates that there is a substantial retention of the labeling still after at least 480 days, i.e. about two-thirds of a rat's life span. Moreover, the appearance of the labeling remains quite distinct. Using established markers for axon damage of DRG neurons, we could detect a slight and transient effect of the peripheral nerve injection on the gene expression pattern. It is concluded that fluorescent microspheres represents an attractive means of tagging neurons in experiments covering long time periods.

Topics: Animals; Axonal Transport; Calcitonin Gene-Related Peptide; Cell Count; Female; Fluorescein; Ganglia, Spinal; GAP-43 Protein; Gene Expression Regulation; Microspheres; Nerve Degeneration; Neuroanatomy; Neurons, Afferent; Neuropeptide Y; Peripheral Nerves; Rats; Rats, Sprague-Dawley; RNA, Messenger; Time Factors

Several types of changes have been reported to occur in dorsal root ganglia following peripheral nerve injury, including loss of neurons and increases and decreases in peptide expression. However, with regard to loss of neurons, results have not been consistent, presumably due to different quantitative methodologies employed and species analyzed. So far, most studies have been conducted on rats; however, with the fast development of the transgenic techniques, the mouse has become a standard model animal in primary sensory research. Therefore we used stereological methods to determine the number of neurons, as well as the expression of galanin message-associated peptide, a marker for galanin-expressing neurons, neuropeptide Y, and calcitonin gene-related peptide in lumbar 5 dorsal root ganglia of both control C57 BL/6J mice and in mice subjected to a 'mid-thigh' sciatic nerve transection (axotomy). In control animals the total number of lumbar 5 dorsal root ganglion neurons was about 12000. Seven days after axotomy, 24% of the dorsal root ganglion neurons were lost (P<0.001), and 54% were lost 28 days after axotomy (P<0.001). With regard to the percentage of peptide-expressing neurons, the results obtained showed that both galanin message-associated peptide (from <1% to about 21%) and neuropeptide Y (from <1% to about 16%) are upregulated, whereas calcitonin gene-related peptide is downregulated (from about 41% to about 14%) following axotomy. Results obtained with retrograde labeling of the axotomized dorsal root ganglion neurons indicate that the neuropeptide regulations may be even more pronounced, if the analysis is confined to the axotomized dorsal root ganglion neurons rather than including the entire neuron population. We also applied conventional profile-based counting methods to compare with the stereological data and, although the results were comparable considering the trends of changes following axotomy, the actual percentage obtained with the two methods differed markedly, both for neuropeptide Y- and, especially, for galanin message-associated peptide-positive neurons. These present results demonstrate that marked species differences exist with regard to the effect of nerve injury on dorsal root ganglion neurons. Thus, whereas no neuron loss is seen in rat up to 4 weeks after a 'mid-thigh' transection [Tandrup et al. (2000) J. Comp. Neurol. 422, 172-180], the present results indicate a dramatic loss already after 1 week in mouse. It is sugges

Topics: Animals; Axotomy; Calcitonin Gene-Related Peptide; Cell Count; Cell Death; Cell Size; Fluorescent Dyes; Galanin; Ganglia, Spinal; Immunohistochemistry; Mice; Mice, Inbred C57BL; Nerve Degeneration; Neuropeptide Y; Neuropeptides; Peripheral Nerve Injuries; Peripheral Nerves; Peripheral Nervous System Diseases; Stilbamidines

Detailed quantitative analysis of the vulnerability of different hippocampal and striatal neurons to global forebrain ischemia has not previously been performed. Here we have studied the survival of immunocytochemically identified neurons using an unbiased stereological method in rats subjected to global forebrain ischemia for 30 min and sacrificed 48 h, 1 week or 4 weeks thereafter. Within the hippocampal formation, there was extensive, progressive loss of CA1 pyramidal neurons and dentate hilar neuropeptide Y (NPY)-positive interneurons. In contrast, no reduction of the number of CA3 and CA4 pyramidal neurons or hilar parvalbumin-positive interneurons was detected. In the dorsolateral striatum, the insult caused a major loss of projection neurons immunoreactive to dopamine- and adenosine 3':5'-monophosphate-regulated phosphoprotein with a molecular weight of 32 kilodalton (DARPP-32). The number of parvalbumin-positive striatal interneurons was significantly reduced, while NPY-positive interneurons were resistant. All striatal cholinergic interneurons survived the ischemic insult. At 48 h following the ischemia, the cholinergic interneurons within the lesioned striatum transiently expressed the p75 neurotrophin receptor (p75(NTR)), as shown by double-label immunocytochemistry. Furthermore, there was a significant increase in the number of choline acetyltransferase (ChAT)- and TrkA-immunoreactive interneurons at 4 weeks after the insult. Injections with the cell mitotic division marker BrdU provided no evidence that the elevated cholinergic cell number was due to neurogenesis. Probably, the higher number of ChAT- and TrkA-positive interneurons reflected increased intracellular levels of the corresponding proteins leading to more cells detectable with immunocytochemistry. This study gives the first quantitative description of the vulnerability of defined hippocampal and striatal neurons after global forebrain ischemia. The ischemia-induced increases of p75(NTR), TrkA and ChAT in cholinergic striatal interneurons at various time points after the insult suggest that neurotrophin signaling might be important for the survival and function of these cells in the post-ischemic phase.

Topics: Animals; Antigens, Surface; Body Weight; Brain Ischemia; Cell Count; Cell Survival; Choline O-Acetyltransferase; Dopamine and cAMP-Regulated Phosphoprotein 32; Fluoresceins; Fluorescent Dyes; Hippocampus; Immunohistochemistry; Interneurons; Male; Neostriatum; Nerve Degeneration; Nerve Tissue Proteins; Neurons; Neuropeptide Y; Organic Chemicals; Parvalbumins; Phosphoproteins; Pyramidal Cells; Rats; Rats, Wistar; Receptor, Nerve Growth Factor; Receptor, trkA

I.p. injections of DSP-4 in male rats decreased norepinephrine (NE) levels to varying degrees throughout the brain with 66.7% reductions in the hypothalamic paraventricular nucleus. Intake of intraorally infused sucrose was reduced for 14 days but daily pellet intake recovered within 5 days post-injection. Intraventricular NE restored intraoral sucrose intake in DSP-4-lesioned rats without affecting controls. Intraventricular infusion of neuropeptide Y (NPY) reduced intraoral intake in controls but had no effect in DSP-4-lesioned rats. NPY markedly inhibited intraoral intake in DSP-4-treated rats that also received NE. These data confirm studies showing that NPY decreases consummatory ingestive behavior and suggest that this inhibition involves ascending noradrenergic projections from locus coeruleus.

Topics: Adrenergic Agents; Animals; Appetite Regulation; Benzylamines; Body Weight; Denervation; Dietary Sucrose; Dose-Response Relationship, Drug; Drug Interactions; Eating; Locus Coeruleus; Male; Nerve Degeneration; Neural Pathways; Neuropeptide Y; Neurotoxins; Norepinephrine; Paraventricular Hypothalamic Nucleus; Proteins; Rats; Rats, Wistar

Expression of C-terminal flanking peptide of neuropeptide Y (CPON) in DRG and cell proliferation (incorporation of BrdU) in sciatic nerve of rats following chronic nerve compression (silicone tubes with different internal diameters) was studied by immunocytochemistry. An increased number of CPON-positive neurons and cells incorporating BrdU was induced on the compressed side, most pronounced when a tight tube was used, while no cells expressed CPON or BrdU in intact nerves. The increase was transient and declined with time. Nerve compression induces transient cell proliferation in the nerve and expression of CPON in nerve cell bodies, but this is of a lesser magnitude than those following nerve transection.

Topics: Animals; Axons; Bromodeoxyuridine; Cell Count; Cell Division; Chronic Disease; Denervation; Disease Models, Animal; Female; Ganglia, Spinal; Immunohistochemistry; Nerve Compression Syndromes; Nerve Degeneration; Neurons, Afferent; Neuropeptide Y; Pain; Peptide Fragments; Rats; Rats, Wistar; Schwann Cells; Sciatic Nerve; Up-Regulation

Botulinum toxin is used to induce transient graded paresis by chemodenervation in the treatment of focal hyperkinetic movement disorders. While the molecular events occurring in motoneurons after mechanical nerve lesioning leading to muscle paresis are well known, they have been investigated to a lesser extent after chemodenervation. We therefore examined the expression of enkephalin (ENK), acidic fibroblast growth factor (aFGF), neurotensin (NT), galanin (GAL), substance P (SP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in rat spinal motoneurons after chemodenervation of the gastrocnemius. In order to precisely localize the motoneurons targeting the injection site, retrograde tracing was performed in additional rats by using Fluorogold injections. ENK expression was upregulated in the region corresponding to the Fluorogold positive motoneurons, but also on the contralateral side and in more distant parts of the spinal cord. The highest upregulation occurred 7 to 14 days after injections and decreased over a period of three months. At 8 days, aFGF was slightly downregulated in all regions studied, single motoneurons showed NT expression, while expression of GAL, SP, VIP, and NPY could be detected neither in controls nor in toxin-treated animals. These alterations in gene expression were strikingly different from those described after axotomy. Our present findings give additional demonstration of the considerable plasticity of the adult spinal cord after botulinum toxin treatment.

Topics: Age Factors; Animals; Botulinum Toxins; Cell Count; Corpus Striatum; Enkephalins; Female; Fibroblast Growth Factor 1; Fluorescent Dyes; Galanin; Gene Expression; Motor Neurons; Muscle Denervation; Muscle, Skeletal; Nerve Degeneration; Neuropeptide Y; Neurotensin; Rats; Rats, Wistar; RNA, Messenger; Spinal Cord; Stilbamidines; Substance P; Vasoactive Intestinal Peptide

Young and old Long-Evans rats respond with fevers of equal magnitude and duration to the brain administration of interleukin-1beta (IL-1beta). Here, we characterized brain regional mRNA expression of cytokine and neuropeptide components in response to the brain administration of IL-1beta. We used specific and highly sensitive RNase protection assays to determine mRNA changes for IL-1beta, IL-1 receptor type I (IL-1RI), IL-1R accessory proteins I and II (IL-1R AcP I and II), IL-1 receptor antagonist (IL-1Ra), transforming growth factor-beta1 (TGF-beta1), glycoprotein 130 (gp 130), leptin receptor (OB-R), neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) in the cerebellum, parieto-frontal cortex, hippocampus, hypothalamus, and midbrain of male young (3-5 months) and old (24-26 months) Long-Evans rats. In both young and old rats, IL-1beta induced a significant up-regulation of cerebellar IL-1Ra, IL-1RI, and TGF-beta1 mRNAs; hippocampal TGF-beta1 mRNA; hypothalamic IL-1beta, IL-1Ra, TGF-beta1, and gp 130 mRNAs; and midbrain IL-1beta and TGF-beta1 mRNAs. There were no age-related differences in any cytokine mRNA levels under basal or IL-1beta-stimulated conditions. Levels of hypothalamic POMC mRNA were different between age groups under basal and stimulated conditions. IL-1R AcP I and leptin receptor did not change in any brain region from either young or old rats, suggesting specificity of transcriptional changes. The data show that old Long-Evans rats are not defective in their capacity to develop an appropriate cytokine response to the brain administration of IL-1beta. The implications of these findings for neuroimmunological-neuroinflammatory and neurotoxic/neurodegenerative processes are discussed.

Topics: Aging; Animals; Brain; Cytokines; Fever; Gene Expression Regulation, Developmental; Injections, Intraventricular; Interleukin 1 Receptor Antagonist Protein; Interleukin-1; Male; Nerve Degeneration; Nerve Tissue Proteins; Neuropeptide Y; Neuropeptides; Organ Specificity; Pro-Opiomelanocortin; Rats; Receptors, Cytokine; Receptors, Interleukin-1; RNA, Messenger; Sialoglycoproteins; Transcription, Genetic; Transforming Growth Factor beta

Different neuropeptide-containing nerve fibers (vasoactive intestinal polypeptide, substance P, neuropeptide Y) and nitric oxide synthase (NOS) positive nerve fibers were investigated to clarify their role in the function of human labial glands using immunohisto- and immunocytochemical techniques. The distribution pattern of all immunoreactive nerve fibers was similar both in the control and in the Sjögren's syndrome specimens. A large number of thin varicose vasoactive intestinal polypeptide and NOS positive nerve fibers were seen around or in close contact with the acini. Some of the immunoreactive nerve fibers were associated with the salivary ducts and blood vessels. Substance P and neuropeptide Y immunoreactive nerve fibers were located mainly around the blood vessels. Immunocytochemistry demonstrated that some of the positive nerve fibers were in direct contact with the acini, blood vessels and with the lymphocytes. The gap between the membranes of immunoreactive nerve terminals and the target cells was 40 to 200 nm. The number of the nerve terminals in Sjögren's syndrome specimens was decreased and some degenerated axons were also found. These results suggest that these neuropeptides and nitric oxide might act as a neurotransmitter in the regulation of secretion and blood flow in the labial glands. These fibers might also alter the neuroimmunological processes, because the investigated neuropeptides are known to be immunoregulators.

Topics: Axons; Blood Vessels; Humans; Immunohistochemistry; Lip; Lymphocytes; Nerve Degeneration; Nerve Endings; Nerve Fibers; Neuropeptide Y; Neuropeptides; Nitric Oxide; Nitric Oxide Synthase; Regional Blood Flow; Salivary Ducts; Salivary Glands, Minor; Sjogren's Syndrome; Substance P; Vasoactive Intestinal Peptide; Vasodilator Agents

Previous studies have demonstrated that adrenalectomy rapidly induces cell death in hippocampal formation. However, these previous studies have involved only qualitative observations or biased estimates. Therefore, the selectivity of the effects of adrenalectomy and the magnitude of changes occurring, remain controversial. The present work employed unbiased stereological tools to examine the effects of adrenalectomy on the number of neurons in, and the volume of, the hippocampal formation. Male rats were adrenalectomized 15, 30 or 120 days before sacrifice at 180 days of age. The total number of neurons in the somal layers and hilus of the hippocampal formation was estimated using the optical fractionator. The volume of the different layers of each subdivision in the hippocampal formation was determined according to the Cavalieri principle. A progressive reduction, reaching 43%, was found in the total number of granule cells. Adrenalectomized animals exhibited a reduction in the volume of all layers of the dentate gyrus. No other region of the hippocampal formation displayed significant cell loss or a reduction in volume. In addition, the main neuronal subpopulations of the dentate gyrus were also evaluated, and a reduction in the total number of GABA- and neuropeptide Y-immunoreactive neurons in the molecular and granule cell layers of adrenalectomized rats was found. No quantitative changes were observed in the hilus. To characterize the glial response to the neuronal degeneration, we estimated the total number of cells immunoreactive for glial fibrillary acidic protein in the dentate gyrus. Although no variation in the total number of glial cells was found, signs of astroglial activation were observed in the adrenalectomized group. The present data strengthen the evidence pointing to the critical role of corticosteroids in maintaining the structural integrity of dentate gyrus.

Topics: Adrenalectomy; Animals; Astrocytes; Body Weight; Cell Count; Dentate Gyrus; gamma-Aminobutyric Acid; Glial Fibrillary Acidic Protein; Interneurons; Male; Nerve Degeneration; Neuropeptide Y; Organ Size; Rats; Rats, Wistar; Somatostatin

To investigate whether differences in vulnerability to free radicals might underlie differences among striatal neurons in their vulnerability to neurodegenerative processes such as occur in ischemia and Huntington's disease, we have analyzed the localization of superoxide free radical scavengers in different striatal neuron types in normal rhesus monkey. Single- and double-label immunohistochemical experiments were carried out using antibodies against the enzymes copper, zinc superoxide dismutase (SOD1), or manganese superoxide dismutase (SOD2), and against markers of various striatal cell types. Our results indicate that the striatal cholinergic and parvalbumin interneurons are enriched in SOD1 and/or SOD2, whereas striatal projection neurons and neuropeptide Y/somatostatin (NPY+/SS+) interneurons express only low levels of both SOD1 and SOD2. We also found that projection neurons of the matrix compartment express significantly higher levels of SOD than those in the striosome compartment. Since projection neurons have been reported to be more vulnerable than interneurons and striosome neurons more vulnerable than matrix neurons to neurodegenerative processes, our results are consistent with the notion that superoxide free radicals are at least partly involved in producing the differential neuron loss observed in the striatum following global brain ischemia or in Huntington's disease.

Topics: Animals; Antibodies; Brain Ischemia; Corpus Striatum; Female; Free Radical Scavengers; Humans; Huntington Disease; Immunohistochemistry; Interneurons; Isoenzymes; Macaca mulatta; Male; Nerve Degeneration; Neurons; Neuropeptide Y; Reperfusion Injury; Somatostatin; Superoxide Dismutase

The expression of galanin and neuropeptide Y (NPY) by primary afferent neurons, including those in the trigeminal (V) system, is markedly up-regulated after peripheral nerve damage and might be expected to influence the response of central somatosensory cells to such damage. In the present study, we assessed the effects of four manipulations that have been used to study development and maintenance of vibrissae-related patterns in the V system-nerve transection, whisker clipping, activity blockade with tetrodotoxin (TTX), and axoplasmic transport attenuation with vinblastine-upon the expression of galanin and NPY by V ganglion cells and their central axons in the V brainstem complex. Both neonatal transection of the infraorbital nerve (ION) and application of vinblastine to it resulted in a marked up-regulation of galanin and NPY in V ganglion cells and their central axon arbors in animals killed on postnatal day 6. Neither whisker clipping nor application of TTX to the ION produced such changes. Both ION transection and application of vinblastine to this nerve resulted in a loss of vibrissae-related cellular patterns in the brainstem, but TTX application and whisker clipping did not. These results raise the possibility that up-regulation of galanin and NPY may play a role in the disappearance of vibrissae-related cellular patterns in the brainstem of rats that sustain neonatal ION damage.

Topics: Animals; Animals, Newborn; Axonal Transport; Brain Mapping; Brain Stem; Galanin; Gene Expression Regulation; Nerve Degeneration; Neuropeptide Y; Rats; Sensory Deprivation; Trigeminal Nuclei; Up-Regulation; Vibrissae

Using immunocytochemistry and in situ hybridization analysis of mRNA, we investigated the changes in the expression of somatostatin and neuropeptide Y (NPY) in the rat hippocampal principal neurons in kindling or after electrically induced status epilepticus (SE), two models of limbic epilepsy associated with different chronic sequelae of seizures and seizure-related neuropathology. At the preconvulsive stage 2 of kindling and after three consecutive tonic-clonic seizures (stage 5) but not after a single-discharge (AD), somatostatin and NPY immunoreactivity (IR) were markedly increased in interneurons of the deep hilus and the polymorphic cell layer and their presumed projections to the outer molecular layer of the dentate gyrus. Increased mRNA levels were observed in the same neurons. NPY IR and mRNA were highly expressed in pyramidal-shaped basket cells at both stages of kindling. IR was similar two days after stages 2 or 5 of kindling while less pronounced effects were observed one week after kindling completion. Peptide-containing neurons in the hilus appeared well preserved in spite of an average of 24% reduction of Nissl stained cells (p < 0.01) in the stimulated and contralateral hippocampus at stage 5. No sprouting of mossy fibres in the inner molecular layer was found as assessed by Timm staining. Thirty days after SE, somatostatin IR was slightly reduced or similar to controls in the ventral dentate gyrus and molecular layer in four or six rats (SE-I group) while in the two other post-SE rats (SE-II), somatostatin IR was lost. These changes were associated with a different extent of neurodegeneration as assessed by cell counting of Nissl stained sections. In the granule cells/mossy fibres NPY-IR was transiently expressed at stage 2 and after a single AD. Differently, NPY-IR was persistently enhanced in the mossy fibres of all post-SE rats particularly in the SE-II group. In these rats, NPY immunoreactive fibres were detected in the infrapyramidal region of the stratum oriens CA3 and in the inner molecular layer of the dentate gyrus very likely labeling sprouted mossy fibres. In the hippocampus proper of kindled rats, somatostatin and NPY IR were respectively enhanced in the stratum lacunosum moleculare, the subiculum and in the alveus while no significant changes were observed after SE. Changes in peptide expression were bilateral and involved both the dorsal and the ventral hippocampus. The lasting modifications in peptides IR and mRNA expressi

Topics: Animals; Dentate Gyrus; Functional Laterality; Hippocampus; Immunohistochemistry; Kindling, Neurologic; Limbic System; Nerve Degeneration; Neuronal Plasticity; Neurons; Neuropeptide Y; Rats; RNA, Messenger; Seizures; Somatostatin

1. A new population of neurons with transient expression of NPY immunoreactivity was described in the developing hamster paraventricular thalamic area. The present study was performed to discover whether this phenomenon is due to programmed cell death or apoptosis. 2. Toward this aim, immunocytochemical and electron microscopic examination of the paraventricular thalamic region, as well as DNA electrophoresis of tissue extracted from the described area, was performed on different stages of embryonic and postnatal development. 3. A sudden increase in neuropeptide Y immunoreactivity (NPY-IR) in the paraventricular thalamic area at embryonic day 14 (E14) was the first symptom of neuronal degeneration. 4. Electron microscopy revealed many neurons with large masses of condensed chromatin within nuclei and extracellular bodies. The affected cells had a convoluted shape and condensed cytoplasm. 5. DNA electrophoresis revealed a ladder of bands between 150 and 1000 bp that is specific for internucleosomal DNA fragmentation. 6. The data strongly suggest that developmental disappearance of NPY-IR neurons within the hamster dorsal thalamic area is due to apoptosis.

Topics: Animals; Apoptosis; Cricetinae; DNA Fragmentation; Gestational Age; Mesocricetus; Microscopy, Electron; Nerve Degeneration; Neurons; Neuropeptide Y; Thalamus

Using immunocytochemistry combined with confocal and electron microscopy, the secretory pathways related to substance P (SP), calcitonin gene-related peptide (CGRP), galanin (GAL), and neuropeptide Y (NPY) were investigated in neurons in rat lumbar (L) 4 and L5 dorsal root ganglia (DRGs) before and after peripheral axotomy. All four peptides were processed through the regulated secretory pathway in many small neurons in normal DRGs, and CGRP through this pathway also in some large neurons. In many small neurons, two neuropeptides could be sorted into the same or separate large dense-core vesicles (LDCVs). The LDCVs had a significantly larger diameter in small as compared to large DRG neurons. Fourteen days after sciatic nerve cut, the levels of SP- and CGRP-like immunoreactivities (-LIs) and the number of LDCVs containing these peptides were markedly reduced, but SP- and CGRP-LIs were still seen in the regulated pathway. GAL-LI was markedly increased in many small neurons and some large neurons and NPY-LI mainly in large neurons. Both peptides were particularly abundant in the Golgi region. In small neurons, the number of LDCVs containing GAL- or NPY-LI was increased, but did not appear to reach the numbers containing SP- or CGRP-LI in normal DRG neurons. After axotomy, CGRP-LI and GAL-LI were often in separate LDCVs. One type of NPY-positive large neurons showed budding off of LDCVs after axotomy, but also some "scattered" labeling in the cytoplasm. In the second type, NPY-LI was mainly found in multivesicular bodies. In several myelinated nerve fibers a "diffuse" distribution of NPY was seen together with some LDCVs containing NPY-LI. In contrast, in unmyelinated nerve fibers, NPY-, GAL-, SP-, and CGRP-LIs were always observed in LDCVs. Thus, both in normal and axotomized DRG neurons, peptides are processed through the regulated pathway. However, in some large neurons, NPY is, in addition, secreted through the constitutive pathway, perhaps as a consequence of limited sorting mechanisms for NPY, i.e., the plasticity of the secretory mechanisms does not match the rate of peptide synthesis after axotomy.

Topics: Animals; Axons; Calcitonin Gene-Related Peptide; Ganglia, Spinal; Immunohistochemistry; Male; Microscopy, Confocal; Microscopy, Electron; Nerve Degeneration; Neural Pathways; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Substance P

Quantitative immunohistochemistry was used to study the innervation of the ureter in adult rats pretreated with capsaicin as neonates (50 mg/kg) or as adults (100-150 mg/kg, 10-22 days prior to being killed) using antibodies against protein gene-product 9.5, neuron-specific enolase, substance P, calcitonin gene-related peptide, neuropeptide Y, dopamine-beta-hydroxylase and vasoactive intestinal polypeptide. The number of calcitonin gene-related peptide- and substance P-containing fibres was reduced in the subepithelial plexus (adult capsaicin treatment < 1%, neonatal treatment < 5% of control), the submucosa (adult treatment < 11%; neonatal treatment < 51%) and in the smooth muscle layer and adventitia (adult treatment < 11%; neonatal treatment < 58%). Fibres immunoreactive for protein gene-product 9.5, a general neuronal marker, were reduced to 11% (adult treatment) or 0.5% (neonatal treatment) in the subepithelial plexus, but unchanged in the other layers, indicating a selective regional degeneration. In the smooth muscle layer the number of neuropeptide Y- and vasoactive intestinal polypeptide-containing nerve fibres was not altered by capsaicin. The number of neuropeptide Y fibres in the subepithelial plexus, however, was significantly increased after adult treatment (174% of control). After neonatal capsaicin treatment the intensity of the neuropeptide Y immunoreactivity was increased, more neuropeptide Y-positive nerve bundles were found and immunoreactive cell bodies were observed regularly in the adventitia of the ureter. The data indicate that capsaicin produces a selective degeneration of most afferent fibres in the subepithelial plexus of the rat ureter. This loss of capsaicin-sensitive afferent nerves evokes neuroplastic changes resulting in a hyperinnervation by neuropeptide Y-immunoreactive, presumably sympathetic fibres. The results suggest a mutual regulation of the pattern and density of innervation of peripheral target tissues by sensory and sympathetic neurons.

Topics: Animals; Antibodies; Capsaicin; Ganglia, Sensory; Immunohistochemistry; Nerve Degeneration; Nerve Fibers; Neuropeptide Y; Rats; Rats, Inbred Strains; Sympathetic Nervous System; Ureter

Somatostatin-, neuropeptide Y-, neurokinin B- and cholecystokinin-containing neurons were investigated in the rat hippocampus in two chronic models of temporal lobe epilepsy, i.e. 30 days after rapid kindling or electrically induced status epilepticus (post-status epilepticus). After rapid kindling, somatostatin immunoreactivity was strongly increased in interneurons and in the outer and middle molecular layer of the dentate gyrus. In four of six post-status epilepticus rats (status epilepticus I rats), somatostatin immunoreactivity was slightly increased in the dorsal but decreased in the ventral dentate gyrus and molecular layer. Somatostatin immunoreactivity decreased in neurons of the dorsal hilus in the two other post-status epilepticus rats investigated, while a complete loss was found in the respective ventral extension (status epilepticus-II rats). These changes were associated with a different extent of neurodegeneration as assessed by Nissl staining. Similarly, neuropeptide Y immunoreactivity was enhanced in neurons of the hilus and in the middle and outer molecular layer of the dentate gyrus in the dorsal hippocampus of rapidly kindled and status epilepticus-I rats. Neuropeptide Y and neurokinin B immunoreactivity was enhanced in the mossy fibers of all post-status epilepticus rats, but not in the rapidly kindled rats. In status epilepticus-II rats, neuropeptide Y-and neurokinin B-positive fibers were also detected in the infrapyramidal region of the stratum oriens of CA3 and in the inner molecular layer of the dentate gyrus in the dorsal and ventral hippocampus respectively, labeling presumably sprouted mossy fibers. Increased staining of neuropeptide Y and neurokinin B was found in the alveus after rapid kindling. Cholecystokinin immunoreactivity was markedly increased in the cerebral cortex, Ammon's horn and the molecular layer of the dentate gyrus in the ventral hippocampus of rapidly kindled and post-status epilepticus rats. The lasting changes in the immunoreactive pattern of various peptides in the hippocampus may reflect functional modifications in the corresponding peptide-containing neurons. These changes may be involved in chronic epileptogenesis, which evolves in response to limbic seizures.

Topics: Animals; Brain; Cholecystokinin; Chronic Disease; Epilepsy, Temporal Lobe; Immunohistochemistry; Male; Nerve Degeneration; Neurokinin B; Neuropeptide Y; Neuropeptides; Rats; Rats, Sprague-Dawley; Somatostatin; Tissue Distribution

Lesions of the nucleus basalis of Meynert (NBM) have been used to mimic, in part, cholinergic deficits occurring in age-related neurodegenerative disorders, i.e., Alzheimer's disease. In our study, the effect of a persistent cholinergic denervation of the fronto-parietal cortex on neuropeptide Y (NPY) and somatostatin (SOM) was examined in young adult (3 months old) and aging (> 18 months old) rats, 1, 3 and 6 months after bilateral stereotaxic NBM lesions with quisqualic acid. In aging, non-lesioned rats a significant decrease in radioimmunologically and immunohistochemically detectable NPY and SOM was found with no further changes after lesions. Morphological markers for these peptidergic populations (cell size and number, NADPH-diaphorase histochemistry, electron microscopy) demonstrated no signs of alterations in both age groups after lesion. Densitometric analysis of peptide fibre networks displayed a heterogeneous response with a significant rarefication in young rats 1 month after the lesion, followed by restoration and a tendency towards increase 6 months post lesioning in individual animals. These findings were confirmed by radioimmunological measurements. Examination of synaptic and cytoskeletal markers, i.e., synaptophysin, GAP-43, MAP-2, Tau-1 and amyloid precursor protein, did not reveal any signs for neuronal reorganization or sprouting. These data are discussed in the context of plasticity and pathology in age-related neurodegenerative disorders with cholinergic impairment.

Topics: Acetylcholinesterase; Aging; Animals; Cerebral Cortex; Choline O-Acetyltransferase; Immunohistochemistry; Male; Microscopy, Immunoelectron; NADPH Dehydrogenase; Nerve Degeneration; Neuronal Plasticity; Neuropeptide Y; Parasympathetic Nervous System; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Somatostatin; Substantia Innominata

The ultrastructure and cellular associations of septal efferent terminals identified by anterograde degeneration with neurons containing neuropeptide Y (NPY) in the rat dentate gyrus were examined quantitatively. For this, the septal complex (i.e., medial septal and diagonal band nuclei) of adult male rats was injected with the neurotoxin ibotenic acid (1%; 150 nl) and following a 2-4-day survival period, the hippocampal formation was processed for the electron microscopic immunocytochemical demonstration of NPY using the avidin-biotin complex method. Terminals with the morphological characteristics of anterograde degeneration, in particular an increase in osmiophilia, and neurons containing NPY-like immunoreactivity (NPY-LI) were most abundant in the hilus of the dentate gyrus. In this region, degenerating terminals (n = 109) were usually small (0.2-0.4 microns in diameter) and formed both asymmetric and symmetric synapses with small (distal) dendrites. The degenerating terminals contacted either single NPY-containing (19%) perikarya or dendrites or unlabeled (48%) perikarya or dendrites. Some degenerating terminals contacted the same perikarya or dendrites as an NPY-containing terminal (11%); these neurons were either immunoreactive for NPY or unlabeled. The remaining degenerating terminals were either directly apposed without glial intervention to unlabeled and NPY-labeled terminals (11%) or lacked associations with any neuronal processes in the plane of section analyzed (11%). The findings demonstrate that ibotenic acid injections in the septal complex can identify septal efferent terminals by degeneration and provide cellular substrates for the direct synaptic regulation as well as presynaptic modulation of hippocampal NPY-containing neurons by septal efferent terminals.

Topics: Animals; Axons; Efferent Pathways; Hippocampus; Immunohistochemistry; Male; Microscopy, Electron; Nerve Degeneration; Nerve Endings; Neurons; Neuropeptide Y; Rats; Rats, Sprague-Dawley; Septum Pellucidum

Neuroanatomical methods were used to determine if cocaine irreversibly injures neurons. Despite acute and chronic high-dose treatments for months that produced stereotyped behavior and seizures, and the use of a sensitive silver impregnation method, we were unable to find any evidence of neuronal damage anywhere in the brain. Since expression of the inducible 72 kDa heat shock protein (HSP72) is a sensitive indicator of potentially toxic neuronal stress, we next determined if cocaine evoked HSP72 expression. Even high doses of cocaine that evoked seizures did not induce HSP72 immunoreactivity anywhere within the brain, whereas kainic acid produced widespread HSP72 immunoreactivity and irreversible injury. Having failed to find indications of frank neurotoxicity, we examined peptide and protein cell marker immunoreactivities in search of cocaine-induced changes. Although cocaine treatment had no obvious effects on the patterns of hippocampal calbindin-D28K, somatostatin-, tyrosine hydroxylase- and parvalbumin immunoreactivities, cocaine reliably altered neuropeptide Y-like immunoreactivity (NPY-LI). Most notably, NPY-LI was expressed in hippocampal dentate granule cells and pyriform cortical neurons, which do not normally express it. Conversely, we noted decreased NPY-LI in dentate hilar neurons that normally do express it. Since both changes in NPY-LI were seen only in cocaine-treated rats that exhibited seizures, the role of seizure activity per se in producing the NPY changes was addressed in normal rats by electrical stimulation of the perforant path. Like cocaine, perforant path stimulation for as little as 15min evoked NPY-LI in granule cells but did not replicate the cocaine-induced decrease in hilar cell NPY-LI. These results suggest that cocaine does not irreversibly injure neurons in the rat, even at doses that induce seizures. However, cocaine produces long-lasting changes in NPY expression that are of unknown functional significance. Our inability to demonstrate cocaine-induced neuronal damage in rats should in no way be taken as evidence of its safety in humans.

Topics: Animals; Cocaine; Drug Administration Schedule; Hippocampus; Immunohistochemistry; Male; Nerve Degeneration; Neurons; Neuropeptide Y; Neurotoxins; Rats; Rats, Sprague-Dawley; Seizures; Silver; Stereotyped Behavior; Time Factors

Progressive supranuclear palsy (PSP) has been associated with degenerative changes in cholinergic and dopaminergic neurons in several brain regions. Since acetylcholine is colocalized with the neuropeptide galanin in certain neuronal populations, we measured the concentration of this neuropeptide and neuropeptide Y in cerebrospinal fluid (CSF) of 11 patients with PSP and in 16 age-matched healthy controls. No significant alterations in the CSF levels of galanin or neuropeptide Y were found.

Topics: Aged; Female; Galanin; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Nerve Degeneration; Neurologic Examination; Neuropeptide Y; Peptides; Reference Values; Supranuclear Palsy, Progressive; Tomography, X-Ray Computed

The first part of this article deals with several aspects of efferents and afferents of the rat basal forebrain cholinergic system (BFChS) studied with anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L). PHA-L tracing of the BFChS efferents revealed topographically differentiated axonal trajectories and patterns of presynaptic endings to the neocortex, mesocortex, olfactory nuclei and hippocampus. Combining this method with second immunolabeling, we identified the muscarinic cholinoceptive neurons in the neocortex and the somatostatinergic neurons in the hippocampus as being directly innervated by the magnocellular basal nucleus and the medial septum, respectively. The prefrontal cortex was identified as a source of afferent input to the basal forebrain cholinergic neurons. This projection also exhibits a topographic organization, which shows a reciprocal relationship with the BFChS efferents to the cortex. The second part of this article describes the anatomical changes of cortical cholinergic and some other neurotransmitter systems after long-term cholinergic denervation in the aged rat cortex. The spared cholinergic projection in the largely denervated areas shows abundant malformations, which are similar in appearance to the anatomical alterations of the surviving cholinergic fibers in dementia of the Alzheimer type (AD). Hypertrophic changes also occur in the serotonergic system. The neuropeptide-Y- and somatostatin-containing cortical systems respond with an increment of their axonal densities, in contrast to the decline of these peptides in AD. Although transsynaptic effects are mediated by long-term cholinergic lesions, they do not support the hypothesis that the cholinergic deficiency is a primary event in the pathophysiology of AD.

Topics: Afferent Pathways; Aging; Amygdala; Animals; Brain; Brain Mapping; Brain Stem; Cerebral Cortex; Cholinergic Fibers; Efferent Pathways; Frontal Lobe; Hippocampus; Male; Microscopy, Electron; Nerve Degeneration; Neurons; Neuropeptide Y; Rats; Rats, Inbred Strains; Receptors, Cholinergic; Receptors, Muscarinic; Septum Pellucidum; Serotonin; Somatostatin; Synapses; Synaptic Transmission

Topics: Aged; Aged, 80 and over; Brain Mapping; Computer Simulation; Female; Galanin; Humans; Locus Coeruleus; Male; Models, Neurological; Nerve Degeneration; Neurons; Neuropeptide Y; Norepinephrine; Parkinson Disease; Peptide Fragments; Peptides

A 32-yr-old man with myotonic dystrophy had a left hemicolectomy performed because of a megacolon. The colonic mucosa, smooth muscle, and connective tissue appeared normal by hematoxylin and eosin and trichrome stains and transmission electron microscopy. In contrast, the myenteric plexus had markedly fewer neurons than normal on the hematoxylin and eosin stains. Silver staining of the plexus revealed degeneration and decreased numbers of argyrophilic neurons, which were smaller and had fewer processes and a more uneven staining quality than controls. Many axons were fragmented, and increased numbers of glial cell nuclei were present in the plexus. Degenerative changes in the neurons were present in a patchy distribution on transmission electron microscopy. Immunohistochemistry revealed a decrease of the substance P- and enkephalin-immunoreactive fibers in the muscularis externa. This suggests that colonic motor dysfunction associated with myotonic dystrophy may be caused by a visceral neuropathy that involves the substance P- and enkephalin-immunoreactive fibers of the smooth muscle.

Topics: Adult; Colon; Enkephalins; Histocytochemistry; Humans; Male; Megacolon; Myenteric Plexus; Myotonic Dystrophy; Nerve Degeneration; Nerve Fibers; Neuropeptide Y; Radiography; Substance P; Vasoactive Intestinal Peptide

Tissue concentrations of the neuropeptide somatostatin and the specific activities of glutamic acid decarboxylase (GAD) were measured in several regions of the central nervous system in young rats, following chronic postnatal administration of methylmercuric chloride. By the beginning of the fourth postnatal week, these animals exhibited clinical signs of a mixed spastic/dyskinetic syndrome with visual deficits. At the onset of neurological impairment, a significant decrease in GAD activity was detected in the occipital cortex (48-49%) and striatum (45-50%) when compared to either normal or weight-matched controls. At one subclinical stage of toxicity, decreased GAD activity was detected only in the occipital cortex (29-30%). Tissue levels of somatostatin did not change significantly in the occipital cortex of methylmercury-treated animals at any stage of the experiment. However, somatostatin levels in the striatum were significantly reduced at the onset of neurological impairment (55-57%) and at one subclinical stage of toxicity (49-54%). Immunohistochemistry for somatostatin- and neuropeptide Y-immunoreactive neurons confirmed a marked loss of cells in the dorsolateral region of the striatum with atrophy of the surviving neurons. In the cerebral cortex of methylmercury-treated animals the morphology and distribution of somatostatin-positive neurons appeared normal. In view of the reported co-localization of GAD and somatostatin in some non-pyramidal neurons of the cerebral cortex, these results indicate that methylmercury-induced lesions of the developing cerebral cortex involve a subpopulation of GABAergic neurons which are not co-localized with somatostatin. In the striatum, where GAD and somatostatin are not co-localized within the same neurons, methylmercury-induced lesions involve both GABAergic and somatostatin-positive neurons.

Topics: Aging; Animals; Cerebral Cortex; Corpus Striatum; Female; Glutamate Decarboxylase; Histocytochemistry; Immunohistochemistry; Interneurons; Male; Methylmercury Compounds; Movement Disorders; NADPH Dehydrogenase; Nerve Degeneration; Neuropeptide Y; Posture; Rats; Rats, Inbred Strains; Somatostatin

Neurons identified by their immunoreactivity with antisera against neuropeptide Y (NPY) were studied in three selected areas of the cerebral cortex in brains from controls and in senile dementia of the Alzheimer type (ATD). Changes were more profound in temporal cortex than in parietal cortex, and more severe in parietal cortex than in frontal cortex, paralleling the severity of neuritic plaque formation and incidence of neurofibrillary tangles in these regions. NPY-i neurons became distorted, with enlarged misshapen cell somata and reduced, thickened, and gnarled dendrites. There was a sharp reduction in the extensiveness and delicacy of the axonal plexus; the reorganized axons were haphazard compared to the normal symmetry of these fibers. Besides the alteration in form and sizes, there were also appreciably fewer cells. Nevertheless, the NPY population is not eliminated. Double-label studies of NPY-i and thioflavin indicate that NPY-i fibers can participate in neuritic plaque formation although not all neuritic plaques contained NPY-i axons and not all NPY-i axons were associated with plaques. The surviving NPY cells were evident in all cortices examined, thus giving rise to the speculation that these peptide neurons may have unusual survival and reorganization potential even in terminal neurological disease.

Topics: Aged; Alzheimer Disease; Axons; Brain Chemistry; Cerebral Cortex; Female; Humans; Immune Sera; Immunoenzyme Techniques; Male; Nerve Degeneration; Nerve Tissue Proteins; Neurons; Neuropeptide Y; Postmortem Changes; Staining and Labeling