RESUMO
Water-induced reordering in ultrathin ionic liquid films has been observed using in situ x-ray photoelectron spectroscopy. An ultrathin layer of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1Im][BF4]) was deposited on a rutile TiO2 (1 1 0) single crystal and exposed to water vapour at a relative humidity of ~70% in an in situ cell. Water was found to adsorb onto the ionic liquid surface, causing a reordering of the ions at the interface. Water initially remained trapped on the ionic liquid surface as the in situ cell was evacuated. This could have negative implications for supported ionic liquid phase catalysis, where reactants and products move in and out of an ionic liquid containing the catalyst. This insight into the behaviour at the water/ionic liquid interface provides a basis for understanding interfacial behaviour in more complex gas/ionic liquid systems.
RESUMO
The basal forebrain cholinergic system, which projects to all cortical areas, is a good model for the study of the responses of central nervous system (CNS) neurons to injury. Much is known about the specific neurotrophic factors of basal forebrain cholinergic neurons, and there are many techniques available to chart the progress of degeneration and recovery of cholinergic neurons after damage. There is also a clinical version of damage to cholinergic neurons which is part of the selective pathology of Alzheimer's disease. In general, CNS neurons do not regenerate well after brain damage. The first part of the review describes how the CNS promotes only limited neuronal regeneration, and that this is because of the presence of inhibitory factors and the lack of growth factors. Despite this, some CNS areas may provide a better environment for CNS regeneration than others. In the second part of the review, the degeneration and regeneration of basal forebrain cholinergic pathways in the adult rat are discussed. It is shown how the collateral sprouting of cholinergic axons occur more readily in the hippocampal formation than in neocortical areas, and that this could be linked with the more neuroplastic properties of the hippocampus. The third part of the review describes how the degeneration of cholinergic pathways in Alzheimer's disease is likely to be secondary to the pathology or degeneration of certain cortical areas. The hypothesis is put forward that the severity of the pathology in highly plastic limbic cortical areas could be linked with their susceptibility to risk factors of Alzheimer's disease such as ageing, and genetic and environmental factors.
Assuntos
Fibras Colinérgicas/fisiologia , Neurônios/fisiologia , Prosencéfalo/citologia , Prosencéfalo/lesões , Adulto , Animais , Humanos , Regeneração Nervosa/fisiologiaRESUMO
GABA(B) receptors are believed to play a role in rhythmic activity in the mammalian brain. The aim of our study was to examine the presynaptic and postsynaptic locations of these receptors in the medial septal diagonal band area (MS/DB), an area known to pace the hippocampus theta rhythm. Whole-cell patch recordings were made from parasagittal MS/DB slices obtained from the 16-25 day rat. Neurons were classified into GABAergic and cholinergic subtypes according to previous electrophysiological criteria. Bath application of the GABA(B) receptor agonist baclofen in the presence of tetrodotoxin, and brief tetanic fiber stimulation in the presence of ionotropic receptor antagonists, provided evidence for the presence of postsynaptic GABA(B) receptor transmission to GABAergic but not cholinergic neurons. Bath application of baclofen, at concentrations too low to elicit postsynaptic activity in MS/DB neurons, significantly reduced the amplitudes of stimulus-evoked ionotropic receptor inhibitory postsynaptic potentials (IPSPs) and excitatory postsynaptic potentials (EPSPs) and the paired pulse depression of these evoked potentials. Baclofen also significantly reduced the frequencies but not the amplitudes of miniature inhibitory postsynaptic currents (IPSCs) and excitatory postsynaptic currents (EPSCs), indicating the presence of presynaptic GABA(B) receptors on GABAergic and glutamatergic terminals in the MS/DB. Baclofen, also at a concentration too low to elicit postsynaptic activity, reduced the frequencies and amplitudes of spontaneous IPSCs and EPSCs recorded in the presence of 200-400 nM kainate. Rhythmic compound IPSCs at theta frequencies were recorded under these conditions in some neurons, and these rhythmic compound IPSCs were disrupted by the activation but not by the inhibition of GABA(B) receptors. These results suggest that GABA(B) receptors modulate rather than generate rhythmic activity in the MS/DB, and that this modulatory effect occurs via receptors located on presynaptic terminals.
Assuntos
Neurônios/metabolismo , Receptores de GABA-A/metabolismo , Septo Pelúcido/citologia , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Animais , Animais Recém-Nascidos , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Bicuculina/farmacologia , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Interações Medicamentosas , Estimulação Elétrica/métodos , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/efeitos da radiação , Agonistas GABAérgicos/farmacologia , Antagonistas GABAérgicos/farmacologia , Técnicas In Vitro , Ácido Caínico/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Potenciais da Membrana/efeitos da radiação , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Inibição Neural/efeitos da radiação , Neurônios/efeitos dos fármacos , Neurônios/efeitos da radiação , Técnicas de Patch-Clamp/métodos , Ácidos Fosfínicos/farmacologia , Propanolaminas/farmacologia , Ratos , Ratos Wistar , Septo Pelúcido/crescimento & desenvolvimento , Bloqueadores dos Canais de Sódio/farmacologia , Tetrodotoxina/farmacologia , Fatores de Tempo , Valina/análogos & derivados , Valina/farmacologiaRESUMO
Neurones in the striatum and substantia nigra (zona compacta) of the rat were divided into several classes according to differences in morphological appearance and ultrastructural localization of acetylcholinesterase (AChE). To determine which of the neurone types form connections between the substantia nigra and striatum, the ultrastructural localization of AChE was combined with retrograde axonal transport of horseradish peroxidase (HRP). The products of the histochemical reactions for HRP and AChE are localized in separate intracellular compartments and so identification of the efferent cell types was possible. In the striatum there are two morphological classes of AChE-containing neurone and two or three varieties of cell which do not stain for the enzyme. Only one neurone type projects to the substantia nigra and this is a cell with no AChE which makes up 96% of the total neurone population. In the substantia nigra there are two types of neurone with AChE: a cell with rather variable amounts of AChE which projects to the striatum, and another rarer type, possibly an interneurone.
Assuntos
Acetilcolinesterase/metabolismo , Corpo Estriado/anatomia & histologia , Substância Negra/anatomia & histologia , Animais , Transporte Axonal , Corpo Estriado/enzimologia , Peroxidase do Rábano Silvestre , Masculino , Vias Neurais/anatomia & histologia , Vias Neurais/enzimologia , Neurônios/enzimologia , Neurônios/ultraestrutura , Ratos , Substância Negra/enzimologiaRESUMO
The distribution of catecholaminergic and cholinergic neurons in the upper brainstem of the ferret were mapped by staining immunohistochemically two adjacent series of sections of brainstem for tyrosine hydroxylase and choline acetyltransferase, respectively. As in other species, large numbers of tyrosine-hydroxylase-positive neurons are localized in the ventral tegmental area (A10), the substantia nigra (A9), and in A8. Tyrosine-hydroxylase-positive neurons in the dorsolateral pontine tegmentum (A4, A6, and A7--the locus coeruleus complex) of the ferret are rather diffusely distributed, as has been observed in other carnivore species such as the cat and the dog, but unlike the cat, these cells in the ferret display a relative uniformity in size and morphology. Choline-acetyltransferase-positive neurons which extend in the ferret's pedunculopontine tegmental nucleus and ventral parabrachial area (Ch5) are relatively large cells that stain intensely for choline acetyltransferase, and their dendrites form prominent bundles in regions where unstained fibre tracts are prevalent. Choline-acetyltransferase-positive neurons distributed in the laterodorsal tegmental nucleus (Ch6) are smaller than the cholinergic cells of Ch5, and they stain less intensely for choline acetyltransferase. Rostrally, there is little overlap between the catecholaminergic cell groups A8, A9, and A10 and the cholinergic cell groups of Ch5 and Ch6. Caudally, the Ch5 neurons extend some considerable extent into the locus coeruleus complex. In the region of overlap, no cells with staining for both tyrosine hydroxylase and choline acetyltransferase were observed, as was ascertained with a double staining method employing a combination of tyrosine hydroxylase immunofluorescence and choline acetyltransferase peroxidase-antiperoxidase immunohistochemistry. In conclusion, the ferret has a typically carnivore pattern for the distribution of catecholaminergic cells in the upper brainstem, and there is a significant overlap between the catecholaminergic and cholinergic cell groups in the dorsolateral pontine tegmentum.
Assuntos
Tronco Encefálico/anatomia & histologia , Carnívoros/anatomia & histologia , Colina O-Acetiltransferase/metabolismo , Furões/anatomia & histologia , Neurônios/fisiologia , Tirosina 3-Mono-Oxigenase/metabolismo , Animais , Tronco Encefálico/enzimologia , Feminino , Imunofluorescência , Neurônios/enzimologia , Especificidade de ÓrgãosRESUMO
Previous studies have indicated that galanin is one of the most abundant peptides in the basal forebrain and that it has a significant modulatory influence on cholinergic transmission. The aim of the present study was to use a light electron microscopic correlation technique to determine whether galanin-immunoreactive terminals form synaptic contacts with basal forebrain cholinergic cells of the rat. Sections from fixed-perfused brains were stained at the light and electron microscopic levels for galanin and choline acetyltransferase immunoreactivity in the same section by using a dual-colour immunohistochemical method. The results showed that galanin-immunoreactive axonal terminals are unevenly distributed in the medial septal nucleus, the diagonal band, and the nucleus basalis. Galanin-positive synapses were most prominent on choline acetyltransferase-positive neurons in the lateral parts of the nucleus of the diagonal band and in the posterior half of the nucleus basalis, which is where there was the greatest overlap between the distribution of galanin-immunoreactive terminals and choline acetyltransferase-positive neurons. The origins of these galanin-positive terminals are not known, but the results confirm that the basal forebrain galaninergic system has a synaptic influence on basal forebrain cholinergic neurons in the rat.
Assuntos
Galanina/metabolismo , Neurônios/metabolismo , Sistema Nervoso Parassimpático/metabolismo , Terminações Pré-Sinápticas/metabolismo , Prosencéfalo/metabolismo , Animais , Gânglios da Base/metabolismo , Gânglios da Base/ultraestrutura , Colina O-Acetiltransferase/metabolismo , Imuno-Histoquímica , Masculino , Microscopia Eletrônica , Sistema Nervoso Parassimpático/citologia , Sistema Nervoso Parassimpático/ultraestrutura , Terminações Pré-Sinápticas/ultraestrutura , Prosencéfalo/citologia , Prosencéfalo/ultraestrutura , Ratos , Ratos Wistar , Sinapses/ultraestruturaRESUMO
The distribution and ultrastructural localization of acetylcholinesterase (AChE) was examined in the substantia nigra of rat and guinea pig. Although the pars compacta, in both species, is clearly defined when stained with thionin, there is an apparent discrepancy in the distribution of AChE at the light microscope level. In the rat substantia nigra the enzyme appears to be concentrated mainly in the pars compacta, whereas in the guinea pig the AChE seems homogeneous throughout the entire substantia nigra. Ultrastructural studies, however, reveal a close correspondence in the morphology of rat and guinea pig substantia nigra. The subcellular localization of AChE is also similar. The between-species discrepancy seen with the light microscope was attributed to relative differences in level of intensity of staining for AChE. In both rat and guinea pig, the enzyme is localized in two types of neuron and in the extracellular space. The ultrastructural distribution of AChE is discussed with reference to neurochemical studies on its release from nigral neurons.
Assuntos
Acetilcolinesterase/metabolismo , Substância Negra/enzimologia , Animais , Membrana Celular/enzimologia , Espaço Extracelular/enzimologia , Complexo de Golgi/enzimologia , Cobaias , Histocitoquímica , Microscopia Eletrônica , Ratos , Especificidade da Espécie , Substância Negra/citologia , Substância Negra/ultraestruturaRESUMO
A survey was made of the density of the cholinergic innervation of different parts of the brainstem of the rat and ferret. Sections of rat and ferret brainstems were stained for choline acetyltransferase (ChAT) immunoreactivity by using a sensitive immunocytochemical method. Adjacent sections were stained for acetylcholinesterase activity or Nissl substance. The density of the distribution of fine calibre, varicose ChAT-positive axons, assumed to represent cholinergic terminals, was categorised arbitrarily into high, medium, or low. A high density of ChAT-positive terminals was found in all or parts of these structures: interpeduncular nucleus, superficial grey layer of the superior colliculus (ferret), intermediate layers of the superior colliculus, lateral part of the central grey (rat), an area medial to the parabigeminal nucleus (rat), pontine nuclei, ventral tegmental nucleus (rat), midline pontine reticular formation, and an area ventral to the exit point of the 5th nerve (ferret). A medium density of ChAT-positive terminals was observed in all or parts of: the substantia nigra zona compacta (ferret), ventral tegmental area (ferret), superficial grey layer of the superior colliculus, intermediate and deep layers of the superior colliculus, lateral central grey, area medial to the parabigeminal nucleus, inferior colliculus, dorsal tegmental nucleus, ventral tegmental nucleus (ferret), pontine nuclei, ventral nucleus of the lateral lemniscus (ferret), midline pontine reticular formation, ventral cochlear nucleus, dorsal cochlear nucleus, lateral superior olive, spinal trigeminal nuclei, prepositus hypoglossal nucleus, lateral reticular nucleus, paragigantocellular nucleus, and the dorsal column nuclei including the cuneate, external cuneate, and gracile nuclei. A low density of ChAT-positive terminals was seen throughout the remainder of the brainstem of the rat and ferret, but these terminals were absent from the medial superior olive, substantia nigra zona reticulata (rat), and the central part of the ferret lateral superior olive. A pericellular-like distribution of ChAT-positive terminals was observed in the ventral cochlear nucleus and in association with some of the cells of the nucleus of the mesencephalic tract of the trigeminal nerve. A climbing fibre type arrangement of ChAT-positive terminals was found in the substantia nigra zona compacta (ferret) and medial reticular formation. In general, the distribution of staining for AChE activity reflected that of the distribution of ChAT immunoreactivity in the brainstem, except in a few regions where there were also species differences in the distribution of ChAT-positive terminals, e.g., in the superficial grey layer of the superior colliculus and in the substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)
Assuntos
Axônios/enzimologia , Tronco Encefálico/enzimologia , Colina O-Acetiltransferase/análise , Furões/anatomia & histologia , Ratos Endogâmicos/anatomia & histologia , Animais , Feminino , Imuno-Histoquímica , RatosRESUMO
The number of ganglion cells in the retina of the postnatal rat has been examined. We estimated both the number of axons in the optic nerve and the number of cells which can be retrogradely labelled with horseradish peroxidase from injections into the brain. In the retina of the newborn rat there are at least twice as many ganglion cells as in the adult rat. By retrograde labelling of the ganglion cells and following transection of their axons 24-48 hrs later we can find no evidence that ganglion cells withdraw their axon without degeneration of the patent cell body. We have found that the excess ganglion cells are lost over the first ten postnatal days and during this period we observe pyknotic nuclei in the ganglion cell layer. From our estimates of the total number of neurones in the ganglion cell layer and the number of ganglion cells found at different ages we conclude that the migration of amacrine cells into the ganglion cell layer occurs in the first five postnatal days.
Assuntos
Nervo Óptico/citologia , Retina/citologia , Fatores Etários , Animais , Animais Recém-Nascidos/anatomia & histologia , Axônios , Contagem de Células , Movimento Celular , Sobrevivência Celular , Neurônios/citologia , Ratos , Retina/crescimento & desenvolvimentoRESUMO
Neurons in the medial septal/diagonal band complex (MS/DB) in vivo exhibit rhythmic burst-firing activity that is phase-locked with the hippocampal theta rhythm. The aim was to assess the morphology of local axon collaterals of electrophysiologically identified MS/DB neurons using intracellular recording and biocytin injection in vitro. Cells were classified according to previous criteria into slow-firing, fast-spiking, regular-spiking, and burst-firing neurons; previous work has suggested that the slow-firing neurons are cholinergic and that the other types are GABAergic. A novel finding was the existence of two types of burst-firing neuron. Type I burst-firing neurons had significantly longer duration after hyperpolarisation potentials when held at -60 mV, and at -75 mV, type I neurons exhibited a low-threshold spike with more rapid activation and inactivation kinetics than those of type II neurons. We have, also for the first time, described the main features of the local axon collaterals of the five neuron types. All filled neurons possessed a main axon that gave forth 1-12 local primary axon collaterals. All electrophysiological types, except for the type I burst-firing neuron, had a main axon that coursed toward the fornix. Myelination of the main axon was a prominent feature of all but the slow-firing neurons. Branching of the primary axon collaterals of the fast-spiking and type I burst-firing neurons was more extensive than that of the other cell types, with those of the slow-firing neurons exhibiting the least branching. All cell types possessed axon collaterals of the en passant type, and some in addition had twiglike or basketlike axon terminals. All cell types made synapses on distal dendrites; a proportion of the fast-spiking and burst-firing cells in addition had basketlike terminals that made synaptic contacts on proximal dendrites and on somata. Two morphological types of somata were postsynaptic to the basket cells: large (20-30-microm) oval cells with dark cytoplasm, and large oval cells with paler cytoplasm, often with an apical dendrite. The presence of lamellar bodies in the large dark neurons suggests that they may be cholinergic neurons, because previous work has localised these structures in some neurons that stain for choline acetyltransferase. Our work suggests therefore that there may be GABAergic neurons in the MS/DB that form basket synaptic contacts on at least two types of target cell, possibly cholinergic and GABAergic neurons, which means that the basket cells could play a key role in the generation of rhythmic activity in the MS/DB.
Assuntos
Potenciais de Ação/fisiologia , Axônios/fisiologia , Axônios/ultraestrutura , Ratos Wistar/fisiologia , Núcleos Septais/citologia , Núcleos Septais/fisiologia , Animais , Axônios/classificação , Membrana Celular/fisiologia , Tamanho Celular/fisiologia , Dendritos/fisiologia , Dendritos/ultraestrutura , Estimulação Elétrica , Lisina/análogos & derivados , Lisina/farmacologia , Vias Neurais/citologia , Vias Neurais/fisiologia , Técnicas de Cultura de Órgãos , Terminações Pré-Sinápticas/classificação , Terminações Pré-Sinápticas/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Ratos , Ratos Wistar/anatomia & histologia , Sinapses/fisiologia , Sinapses/ultraestruturaRESUMO
Different doses of the excitotoxin quisqualate were used to make lesions in the caudal part of the ferret nucleus basalis, i.e. the part that projects to the visual cortex. The higher doses of the excitotoxin destroyed all nerve growth factor receptor-immunoreactive cells in the caudal nucleus basalis and gave rise to up to 75% loss of acetylcholinesterase-containing axons in the visual cortex. In sections stained for Nissl substance there was generalized tissue damage around the injection sites and extensive loss of all neuron types in areas surrounding the caudal nucleus basalis. Lower doses of the excitotoxin damaged only a proportion of the nerve growth factor receptor-immunoreactive neurons in the caudal nucleus basalis and produced a much lower depletion of acetylcholinesterase-positive fibres in the visual cortex. The only damage seen in sections stained for Nissl substance was a loss of magnocellular neurons in the vicinity of the injection sites. A quantitative morphological approach was used to show that either one week or three months after the lesions there was a linear correlation between the proportion of acetylcholinesterase-positive axons lost in the visual cortex and the proportion of nerve growth factor receptor-immunoreactive cells that had disappeared from the caudal nucleus basalis. Since the correlation lines for the short-term (one week) survival and the long-term (three months) survival experiments coincided, this indicated that no collateral sprouting of cholinergic axons had occurred in the visual cortex of the long-term survival animals regardless of size of the lesion in the nucleus basalis.
Assuntos
Fibras Colinérgicas/fisiologia , Córtex Visual/patologia , Acetilcolinesterase/análise , Animais , Transporte Axonal , Axônios/efeitos dos fármacos , Axônios/fisiologia , Fibras Colinérgicas/efeitos dos fármacos , Furões , Degeneração Neural , Fatores de Crescimento Neural/metabolismo , Regeneração Nervosa , Ácido Quisquálico/toxicidade , Ratos , Receptores de Superfície Celular/análise , Receptores de Fator de Crescimento Neural , Córtex Visual/enzimologiaRESUMO
The aim of this study was to examine the development of the basalocortical pathway by using choline acetyltransferase and nerve growth factor receptor immunocytochemistry, acetylcholinesterase histochemistry and retrograde axonal transport. The observations were made in the ferret because in this species brain development occurs over a much more protracted period than in the rat. Staining for choline acetyltransferase immunoreactivity in the brain was minimal before birth. Adult levels of staining for the enzyme were not seen in cell bodies until three weeks after birth and in axons up to six weeks after birth. This, however, did not mean that presumptive cholinergic pathways are absent early in development. There was strong staining for nerve growth factor receptor in basal forebrain neurons from at least two weeks before birth. Positive staining for acetylcholinesterase was found in axons that begin to invade the cerebral cortex a week before birth. The retrograde axonal transport technique showed that the basalocortical pathway has a normal organization in the neonate. The conclusion is that cholinergic pathways form early in the prenatal period in the ferret but express their transmitter function late in postnatal development.
Assuntos
Córtex Cerebral/citologia , Sistema Nervoso Parassimpático/embriologia , Substância Inominada/citologia , Acetilcolinesterase/metabolismo , Animais , Animais Recém-Nascidos , Axônios/metabolismo , Transporte Biológico , Córtex Cerebral/embriologia , Córtex Cerebral/crescimento & desenvolvimento , Córtex Cerebral/metabolismo , Colina O-Acetiltransferase/metabolismo , Desenvolvimento Embrionário e Fetal , Furões , Sistema Nervoso Parassimpático/crescimento & desenvolvimento , Receptores de Superfície Celular/metabolismo , Receptores de Fator de Crescimento Neural , Substância Inominada/embriologia , Substância Inominada/crescimento & desenvolvimento , Substância Inominada/metabolismo , Transmissão Sináptica , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
A previous in situ hybridization study by Wisden et al., J. Neurosci. 12, 1040-1062, showed a high expression of the GABAA receptor alpha 1, beta 2 and gamma 2 subunit messenger RNAs in the medial septal nucleus and nucleus of the diagonal band of the rat. The aim of the present study was to determine whether this high expression of GABAA receptor subunit messenger RNAs is found in the cholinergic neurons of these areas. Adjacent 4-5 microns sections of rat forebrain were submitted to choline acetyltransferase immunocytochemistry or to in situ hybridization histochemistry using oligonucleotides complementary to parts of the GABAA receptor alpha 1, alpha 2, beta 2, delta 1 and gamma 2 subunit messenger RNAs. It was found that the high expression for the GABAA receptor alpha 1, beta 2 and gamma 2 subunit messenger RNAs in the medial septal nucleus, the nucleus of the diagonal band and the nucleus basalis is located almost exclusively in non-cholinergic neurons. It was also found that these non-cholinergic cells are also continuous in distribution with neurons in the globus pallidus and ventral pallidum that similarly express high levels of messenger RNA for the GABAA receptor alpha 1, beta 2 and gamma 2 subunits. It was concluded that the basal forebrain cholinergic neurons may not be as sensitive to GABAA receptor influences as their non-cholinergic neighbours.
Assuntos
Sistema Nervoso Autônomo/metabolismo , Neurônios/metabolismo , Prosencéfalo/metabolismo , RNA Mensageiro/biossíntese , Receptores de GABA-A/biossíntese , Animais , Sistema Nervoso Autônomo/citologia , Sistema Nervoso Autônomo/enzimologia , Sequência de Bases , Colina O-Acetiltransferase/biossíntese , Feminino , Imuno-Histoquímica , Hibridização In Situ , Masculino , Dados de Sequência Molecular , Neurônios/enzimologia , Prosencéfalo/citologia , Prosencéfalo/enzimologia , Ratos , Ratos WistarRESUMO
Previous studies have shown that the striatum provides synaptic inputs to the globus pallidus and entopeduncular nucleus in which GABA is co-localized with the peptides enkephalin and substance P. The aim of this study in the rat was to determine whether the striatal projections also make synaptic contact with the cholinergic neurons of the nucleus basalis, which lie near to the pallidal areas in the rat brain. The anterograde tracer biocytin was injected into different parts of the striatum, and brain sections were stained for biocytin and choline acetyltransferase immunoreactivity by using a dual colour method. Terminals labelled with biocytin by anterograde transport and which made synaptic contact with choline acetyltransferase-positive soma and dendrites were identified by light-electron microscopic correlation methods. In the cases where the biocytin injections had been made in the dorsal or lateral striatum, biocytin-labelled terminals made synaptic contact with cholinergic cells in the region between the main termination zones in the globus pallidus and the entopeduncular nucleus. In the cases where the injections had been made in the ventromedial and posterior striatum, there was greater overlap between choline acetyltransferase-positive structures and biocytin-labelled terminals in the main termination zones in the globus pallidus or entopeduncular nucleus, but relatively few of these terminals made synaptic contacts on to the cholinergic neurons. The results therefore indicate that the cholinergic nucleus basalis cells receive a relatively sparse synaptic input from all parts of the striatum. It has recently been shown that the cholinergic cells of the nucleus basalis selectively express high levels of substance P and opioid receptor messenger RNAs, while the non-cholinergic pallidal cells have much higher levels of GABA(A) receptor subunit messenger RNAs. It is concluded that the cholinergic neurons of the nucleus basalis in the rat may be selectively responsive to the peptidergic components of the striatal outputs, and that they are most likely to be influenced by both the limbic and sensorimotor parts of the striatum.
Assuntos
Corpo Estriado/fisiologia , Prosencéfalo/fisiologia , Transmissão Sináptica , Acetilcolinesterase/metabolismo , Animais , Corpo Estriado/metabolismo , Globo Pálido/metabolismo , Globo Pálido/fisiologia , Globo Pálido/ultraestrutura , Lisina/análogos & derivados , Masculino , Microscopia Eletrônica , Terminações Nervosas/ultraestrutura , Prosencéfalo/metabolismo , Prosencéfalo/ultraestrutura , Ratos , Ratos Wistar , Sinapses/fisiologia , Sinapses/ultraestruturaRESUMO
A combination of choline acetyltransferase immunohistochemistry and acetylcholinesterase histochemistry was used to characterize the ultrastructural distribution of acetylcholinesterase in identified cholinergic and non-cholinergic neurons in the ferret brain. Previous studies have shown that most of the cholinergic input to the brain arises from choline acetyltransferase-positive neurons found in the neostriatum, basal forebrain and dorsolateral pontine tegmentum. In all these cells intense staining for acetylcholinesterase was localized within the cisternae of the rough endoplasmic reticulum, in the nuclear envelope and Golgi apparatus, and along the plasma membranes of the soma and dendrites. In contrast, the distribution of acetylcholinesterase in non-cholinergic neurons was restricted mainly to the cisternae of the endoplasmic reticulum and the nuclear envelope. Since previous studies have associated high levels of acetylcholinesterase staining with non-cholinergic neurons in the locus coeruleus and substantia nigra zona compacta, these areas were examined as well. The ultrastructural localization of acetylcholinesterase in the principal locus coeruleus neurons was as observed in typical non-cholinergic neurons. On the other hand, the distribution of acetylcholinesterase in the principal cells of the zona compacta of the substantia nigra was more like that found in cholinergic neurons. In conclusion, the subcellular distribution of acetylcholinesterase in the principal cholinergic neurons of the brain follows a characteristic pattern which, with one exception, is different from that of acetylcholinesterase-positive non-cholinergic neurons.
Assuntos
Acetilcolinesterase/metabolismo , Encéfalo/enzimologia , Dendritos/enzimologia , Neurônios/enzimologia , Sistema Nervoso Parassimpático/enzimologia , Animais , Encéfalo/ultraestrutura , Colina O-Acetiltransferase/metabolismo , Feminino , Furões , Histocitoquímica , Imuno-Histoquímica , Locus Cerúleo/enzimologia , Masculino , Microscopia Eletrônica , Neurônios/ultraestrutura , Sistema Nervoso Parassimpático/ultraestrutura , Coloração e Rotulagem , Substância Negra/enzimologia , Distribuição TecidualRESUMO
The distribution of acetylcholinesterase and choline acetyltransferase in primary visual areas of adult pigmented ferret was determined with cholinesterase histochemistry and choline acetyltransferase immunohistochemistry. In all visual areas the distribution of acetylcholinesterase in the neuropil closely matches that of choline acetyltransferase. In the cerebral cortex acetylcholinesterase and choline acetyltransferase are associated with axons found in every cortical layer and in the white matter. Area 17, identified by Nissl architectonics and cytochrome oxidase histochemistry, is distinguished by having a relatively low density of choline acetyltransferase- and acetylcholinesterase-stained axons in layer IV. Certain cortical non-pyramidal cell types show moderate staining for acetylcholinesterase after relatively long incubations, but no choline acetyltransferase-positive cells are observed in the cortex. In the lateral geniculate nucleus and superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are considerably higher than in cerebral cortex, and choline acetyltransferase-stained axons there display prominent varicosities. The distribution of choline acetyltransferase and acetylcholinesterase in the neuropil of lateral geniculate nucleus and superior colliculus of ferret shows marked laminar variation. For instance, in the lateral geniculate nucleus, the levels of acetylcholinesterase and choline acetyltransferase in the "On" sublaminae of laminae A and A1 are higher than the "Off" sublaminae. In the superficial layers of the superior colliculus the levels of choline acetyltransferase and acetylcholinesterase are highest in the stratum zonale and lowest in the stratum opticum; in the intermediate gray layer of the superior colliculus acetylcholinesterase- and choline acetyltransferase-stained fibres are distributed into dense patches. As in cortex, choline acetyltransferase-positive cell bodies are not found in the lateral geniculate nucleus or superior colliculus, and acetylcholinesterase-stained cell bodies are visible only after long incubations. Cell bodies staining positively for choline acetyltransferase are found in a satellite of the superior colliculus, the parabigeminal nucleus.
Assuntos
Carnívoros/anatomia & histologia , Furões/anatomia & histologia , Vias Visuais/anatomia & histologia , Acetilcolinesterase/metabolismo , Animais , Colina O-Acetiltransferase/metabolismo , Fibras Colinérgicas , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Corpos Geniculados/enzimologia , Histocitoquímica , Técnicas Imunoenzimáticas , Colículos Superiores/enzimologia , Córtex Visual/enzimologia , Vias Visuais/enzimologiaRESUMO
A combination of retrograde axonal tract tracing and choline acetyltransferase immunocytochemistry was used to determine the cells of origin of the cholinergic innervation of the rat cochlear nucleus. The results showed that the cochlear nucleus receives a major cholinergic input from a group of small cells found in the ventral trapezoid nucleus. Experiments using an anterograde tracer confirmed the presence of a neuronal pathway from the ventral trapezoid nucleus to the cochlear nucleus and showed that this pathway travels via the trapezoid body.
Assuntos
Núcleo Coclear/fisiologia , Neurônios/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Ponte/fisiologia , Animais , Vias Autônomas/citologia , Vias Autônomas/fisiologia , Axônios/fisiologia , Benzofuranos , Colina O-Acetiltransferase/imunologia , Colina O-Acetiltransferase/metabolismo , Núcleo Coclear/citologia , Peroxidase do Rábano Silvestre , Imuno-Histoquímica , Lisina/análogos & derivados , Masculino , Sistema Nervoso Parassimpático/citologia , Ponte/citologia , Ratos , Ratos Wistar , Conjugado Aglutinina do Germe de Trigo-Peroxidase do Rábano Silvestre , Aglutininas do Germe de TrigoRESUMO
The ventrobasal thalamus and adjacent regions were stained for the presence of N-acetylaspartylglutamate-like immunoreactivity. Immunoreactive axonal terminals were observed in this area and also in certain non-specific thalamic nuclei, the reticular thalamic nucleus and the lateral geniculate nucleus. Stained somata were found in the habenula, centrolateral thalamic nucleus and reticular thalamic nucleus. Iontophoretically applied N-acetylaspartylglutamate had variable, although predominantly inhibitory, actions on ventrobasal thalamus neurons. These results indicate that N-acetylaspartylglutamate is unlikely to be the neurotransmitter of ascending somatosensory afferents, but do not rule out the possibility that it has some other neurotransmitter or neuromodulator role in the ventrobasal thalamus.
Assuntos
Dipeptídeos/análise , Tálamo/análise , Potenciais de Ação/efeitos dos fármacos , Animais , Dipeptídeos/farmacologia , Imuno-Histoquímica , Ratos , Tálamo/efeitos dos fármacos , Tálamo/fisiologiaRESUMO
The decussation patterns of retinal ganglion cells in adult pigmented and albino ferrets were determined from the distribution of cells labelled after large unilateral injections of horseradish peroxidase into the visual pathway, involving the lateral geniculate nucleus and fibres of passage to the superior colliculus. About 6000 retinal ganglion cells project ipsilaterally in pigmented ferrets compared with only about 1500 in albino ferrets. In both strains, the vast majority of these cells (99 and 87% in pigmented and albino animals, respectively) are located in the temporal crescent, although we describe one albino ferret in which an aberrant uncrossed projection arises from nasal retina. In pigmented ferrets, there is a sharp nasotemporal division that runs through the area centralis; a small proportion of the ganglion cells in temporal crescent (less than 10%) does project contralaterally. In albinos, however, the majority of cells in temporal retina project contralaterally. There is no clear nasotemporal division in the albino retina; the density of uncrossed ganglion cells is reduced throughout temporal crescent and at no location exceeds the comparable density of the crossed projection. The peak density within the reduced uncrossed projection is also displaced away from the area centralis into temporal retina. Analysis of cell type on the basis of soma size indicates that whereas large horseradish peroxidase injections into the visual pathway of pigmented ferrets label all types of ganglion cell in the crossed projection, injections restricted to the superior colliculus label only those ganglion cells with large or small somata. The distribution of cell sizes in the crossed projection from temporal retina is biased towards small cells in the pigmented ferret but in albinos resembles that seen in the crossed projection from nasal retina. Thus the adult pigmented ferret has both a well developed nasotemporal division in which decussation lines are obvious in the crossed and uncrossed pathways and also, unlike rodents but like cats, a class of ganglion cell that does not project to the superior colliculus. The albino mutation both reduces the uncrossed projection throughout temporal retina, although the reduction is greatest close to the area centralis, and also commensurately increases the crossed projection from temporal retina.
Assuntos
Albinismo/patologia , Carnívoros/anatomia & histologia , Furões/anatomia & histologia , Corpos Geniculados/citologia , Retina/citologia , Células Ganglionares da Retina/citologia , Colículos Superiores/citologia , Animais , Gatos , Contagem de Células , Feminino , Variação Genética , Masculino , Ratos , Especificidade da Espécie , Vias Visuais/anormalidades , Vias Visuais/citologiaRESUMO
During fetal development of the cat's visual system there is a marked overproliferation of optic nerve axons. In utero binocular interaction contributes to the severity of fiber loss since removal of an eye during gestation attenuates axon loss in the remaining optic nerve. The purpose of the present study was to determine whether this reduced loss of optic nerve fibers is due to a failure of retraction by supernumerary axon branches or to a reduction in ganglion cell death. To resolve this issue, we compared the number of ganglion cells and optic nerve fibers in adult cats which had one eye removed at known gestational ages. Retinal ganglion cells were backfilled with horseradish peroxidase and counts were made from retinal wholemounts. The axon complement was assessed with an electron microscopic assay. In the retinas of a normal cat we estimated 151,000 and 152,000 ganglion cells. The optic nerves of two other normal cats contained approximately 158,000 and 159,000 axons. In comparison, an animal enucleated on embryonic day 42 had 180,000 ganglion cells and 178,000 optic nerve fibers, while in an animal enucleated on embryonic day 51 the corresponding estimates were 182,000 and 190,000. The close agreement between cell and fiber counts indicates that axonal bifurcation does not contribute appreciably to the axon surplus in the optic nerve of prenatally enucleated cats. These results demonstrate that prenatal binocular interaction regulates the size of the mature retinal ganglion cell population.