Distribution of neurotensin immunoreactivity within the human amygdaloid complex: a comparison with acetylcholinesterase- and Nissl-stained tissue sections

The amygdaloid body of two carnivore species: The feliform banded mongoose and the caniform domestic ferret

The current study provides an analysis of the cytoarchitecture, myeloarchitecture, and chemoarchitecture of the amygdaloid body of the banded mongoose (Mungos mungo) and domestic ferret (Mustela putorius furo). Using architectural and immunohistochemical stains, we observe that the organization of the nuclear and cortical portions of the amygdaloid complex is very similar in both species. The one major difference is the presence of a cortex-amygdala transition zone observed in the domestic ferret that is absent in the banded mongoose. In addition, the chemoarchitecture is, for the most part, quite similar in the two species, but several variances, such as differing densities of neurons expressing the calcium-binding proteins in specific nuclei are noted. Despite this, certain aspects of the chemoarchitecture, such as the cholinergic innervation of the magnocellular division of the basal nuclear cluster and the presence of doublecortin expressing neurons in the shell division of the accessory basal nuclear cluster, appear to be consistent features of the Eutherian mammal amygdala. The domestic ferret presented with an overall lower myelin density throughout the amygdaloid body than the banded mongoose, a feature that may reflect artificial selection in the process of domestication for increased juvenile-like behavior in the adult domestic ferret, such as a muted fear response. The shared, but temporally distant, ancestry of the banded mongoose and domestic ferret allows us to generate observations relevant to understanding the relative influence that phylogenetic constraints, adaptive evolutionary plasticity, and the domestication process may play in the organization and chemoarchitecture of the amygdaloid body.

Neuropeptides Exert Neuroprotective Effects in Alzheimer's Disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by cognitive deficits and neuronal loss. Deposition of beta-amyloid peptide (Aβ) causes neurotoxicity through the formation of plaques in brains of Alzheimer's disease. Numerous studies have indicated that the neuropeptides including ghrelin, neurotensin, pituitary adenylate cyclase-activating polypeptide (PACAP), neuropeptide Y, substance P and orexin are closely related to the pathophysiology of Alzheimer's disease. The levels of neuropeptides and their receptors change in Alzheimer's disease. These neuropeptides exert neuroprotective roles mainly through preventing Aβ accumulation, increasing neuronal glucose transport, increasing the production of neurotrophins, inhibiting endoplasmic reticulum stress and autophagy, modulating potassium channel activity and hippocampal long-term potentiation. Therefore, the neuropeptides may function as potential drug targets in the prevention and cure of Alzheimer's disease.

Receptor-driven, multimodal mapping of the human amygdala

The human amygdala consists of subdivisions contributing to various functions. However, principles of structural organization at the cellular and molecular level are not well understood. Thus, we re-analyzed the cytoarchitecture of the amygdala and generated cytoarchitectonic probabilistic maps of ten subdivisions in stereotaxic space based on novel workflows and mapping tools. This parcellation was then used as a basis for analyzing the receptor expression for 15 receptor types. Receptor fingerprints, i.e., the characteristic balance between densities of all receptor types, were generated in each subdivision to comprehensively visualize differences and similarities in receptor architecture between the subdivisions. Fingerprints of the central and medial nuclei and the anterior amygdaloid area were highly similar. Fingerprints of the lateral, basolateral and basomedial nuclei were also similar to each other, while those of the remaining nuclei were distinct in shape. Similarities were further investigated by a hierarchical cluster analysis: a two-cluster solution subdivided the phylogenetically older part (central, medial nuclei, anterior amygdaloid area) from the remaining parts of the amygdala. A more fine-grained three-cluster solution replicated our previous parcellation including a laterobasal, superficial and centromedial group. Furthermore, it helped to better characterize the paralaminar nucleus with a molecular organization in-between the laterobasal and the superficial group. The multimodal cyto- and receptor-architectonic analysis of the human amygdala provides new insights into its microstructural organization, intersubject variability, localization in stereotaxic space and principles of receptor-based neurochemical differences.

Failing as doorman and disc jockey at the same time: Amygdalar dysfunction in Parkinson's disease

In Braak's model of ascending degeneration in Parkinson's disease (PD), involvement of the amygdala occurs simultaneously with substantia nigra degeneration. However, the clinical manifestations of amygdalar involvement in PD have not been fully delineated. Considered a multitask manager, the amygdala is a densely connected "hub," coordinating and integrating tasks ranging from prompt, multisensorial emotion recognition to adequate emotional responses and emotional tuning of memories. Although phylogenetically predisposed to handle fear, the amygdala handles both aversive and positive emotional inputs. In PD, neuropathological and in vivo studies suggest primarily amygdalar hypofunction. However, as dopamine acts as an inverted U-shaped amygdalar modulator, medication-induced hyperactivity of the amygdala can occur. We propose that amygdalar (network) dysfunction contributes to reduced recognition of negative emotional face expressions, impaired theory of mind, reactive hypomimia, and impaired decision making. Similarly, impulse control disorders in predisposed individuals, hallucinations, anxiety, and panic attacks may be related to amygdalar dysfunction. When available, we discuss amygdala-independent trigger mechanisms of these symptoms. Although dopaminergic agents have mostly an activation effect on amygdalar function, adaptive and compensatory network changes may occur as well, but these have not been sufficiently explored. In conclusion, our model of amygdalar involvement brings together several elements of Parkinson's disease phenomenology heretofore left unexplained and provides a framework for testable hypotheses in patients during life and in autopsy analyses.

The human medial amygdala: structure, diversity, and complexity of dendritic spines

The medial nucleus of the amygdala (Me) is a component of the neural circuit for the interpretation of multimodal sensory stimuli and the elaboration of emotions and social behaviors in primates. We studied the presence, distribution, diverse shape, and connectivity of dendritic spines in the human Me of adult postmortem men. Data were obtained from the five types of multipolar neurons found in the Me using an adapted Golgi method and light microscopy, the carbocyanine DiI fluorescent dye and confocal microscopy, and transmission electron microscopy. Three-dimensional reconstruction of spines showed a continuum of shapes and sizes, with the spines either lying isolated or forming clusters. These dendritic spines were classified as stubby/wide, thin, mushroom-like, ramified or with an atypical morphology including intermediate shapes, double spines, and thorny excrescences. Pleomorphic spines were found from proximal to distal dendritic branches suggesting potential differences for synaptic processing, strength, and plasticity in the Me neurons. Furthermore, the human Me has large and thin spines with a gemmule appearance, spinules, and filopodium. The ultrastructural data showed dendritic spines forming monosynaptic or multisynaptic contacts at the spine head and neck, and with asymmetric or symmetric characteristics. Additional findings included en passant, reciprocal, and serial synapses in the Me. Complex long-necked thin spines were observed in this subcortical area. These new data reveal the diversity of the dendritic spines in the human Me likely involved with the integration and processing of local synaptic inputs and with functional implications in physiological and various neuropathological conditions.

Developmental dynamics of neurotensin binding sites in the human hypothalamus during the first postnatal year

The aim of the present study was to determine a detailed mapping of neurotensin (NT) in the human hypothalamus, during the first postnatal year using an in vitro quantitative autoradiography technique and the selective radioligand monoiodo-Tyr3-NT. Ten human postmortem hypothalami obtained from control neonates and infants (aged from 2 h to 1 year of postnatal age) were used. The biochemical kinetics of the binding in all obtained in this study revealed that the binding affinity constants were of high affinity (in the nanomolar range) and did not differ significantly between all cases investigated. Furthermore, competition experiments show insensitivity to levocabastine and were in favor of the presence of the high affinity site of NT receptor. Autoradiographic distribution showed that NT binding sites were widely distributed throughout the rostrocaudal extent of the hypothalamus. However, the distribution of NT binding sites was not homogenous and regional variations exist. In general, the highest densities were mainly present in the anterior hypothalamic level, particularly in the preoptic area. High NT binding site densities are also present at the mediobasal hypothalamic level, particularly in the paraventricular, parafornical, and dorsomedial nuclei. At the posterior level, low to very low densities could be observed in all the mammillary complex subdivisions, as well as the posterior hypothalamic area. Although this topographical distribution is almost identical during the postnatal period analyzed, age-related variations exist in discrete structures of the hypothalamus. The densities were higher in neonates/less aged infants than older infants in preoptic area (medial and lateral parts). The developmental profile is characterized by a progressive decrease from the neonate period to 1 year of postnatal age with a tendency to reach adult levels. On the other hand, the low levels of NT binding sites observed in posterior hypothalamus did not vary during the first postnatal year. They contrast in that with the very high levels we reported previously in adult. In conclusion, the present study demonstrates the occurrence of high NT binding sites density in various structures in many regions in the human neonate/infant hypothalamus, involved in the control of neuroendocrine and/or neurovegetative functions.

Cellular components of the human medial amygdaloid nucleus

The medial nucleus (Me) is a superficial component of the amygdaloid complex. Here we assessed the density and morphology of the neurons and glial cells, the glial fibrillary acidic protein (GFAP) immunoreactivity, and the ultrastructure of the synaptic sites in the human Me. The optical fractionator method was applied. The Me presented an estimated mean neuronal density of 1.53 × 10⁵ neurons/mm³ (greater in the left hemisphere), more glia (72% of all cells) than neurons, and a nonneuronal:neuronal ratio of 2.7. Golgi-impregnated neurons had round or ovoid, fusiform, angular, and polygonal cell bodies (10-30 μm in diameter). The length of the dendrites varied, and pleomorphic spines were found in sparsely spiny or densely spiny cells (1.5-5.2 spines/dendritic μm). The axons in the Me neuropil were fine or coarsely beaded, and fibers showed simple or notably complex collateral terminations. The protoplasmic astrocytes were either isolated or formed small clusters and showed GFAP-immunoreactive cell bodies and multiple branches. Furthermore, we identified both asymmetrical (with various small, clear, round, electron-lucent vesicles and, occasionally, large, dense-core vesicles) and symmetrical (with small, flattened vesicles) axodendritic contacts, also including multisynaptic spines. The astrocytes surround and may compose tripartite or tetrapartite synapses, the latter including the extracellular matrix between the pre- and the postsynaptic elements. Interestingly, the terminal axons exhibited a glomerular-like structure with various asymmetrical contacts. These new morphological data on the cellular population and synaptic complexity of the human Me can contribute to our knowledge of its role in health and pathological conditions.

Where and what is the paralaminar nucleus? A review on a unique and frequently overlooked area of the primate amygdala

The primate amygdala is composed of multiple subnuclei that play distinct roles in amygdala function. While some nuclei have been areas of focused investigation, others remain virtually unknown. One of the more obscure regions of the amygdala is the paralaminar nucleus (PL). The PL in humans and non-human primates is relatively expanded compared to lower species. Long considered to be part of the basal nucleus, the PL has several interesting features that make it unique. These features include a dense concentration of small cells, high concentrations of receptors for corticotropin releasing hormone and benzodiazepines, and dense innervation of serotonergic fibers. More recently, high concentrations of immature-appearing cells have been noted in the primate PL, suggesting special mechanisms of neural plasticity. Following a brief overview of amygdala structure and function, this review will provide an introduction to the history, embryology, anatomical connectivity, immunohistochemical and cytoarchitectural properties of the PL. Our conclusion is that the PL is a unique subregion of the amygdala that may yield important clues about the normal growth and function of the amygdala, particularly in higher species.

The distribution pattern of pathology and cholinergic deficits in amygdaloid complex in Alzheimer's disease and dementia with Lewy bodies

We studied the distribution pattern of pathology and cholinergic deficits in the subnuclei of the amygdaloid complex (AC) in five patients with Alzheimer's disease (AD), eight with dementia with Lewy bodies (DLB) and five normal controls. In controls, the basal nucleus contained the highest choline acetyltransferase activity; the activity in the lateral and central nuclei and those in the cortical, medial and accessory basal nuclei were comparable. In AD, there was a significant decrease in choline acetyltransferase activity in the accessory basal and lateral nuclei, in DLB a significant decrease was observed in the accessory basal, lateral and cortical nuclei. Compared to controls the hyperphosphorylated tau-pathology burden was significantly higher in the basal, central and medial nuclei in AD and in the central, cortical, lateral and medial nuclei in DLB. The amyloid plaque burden was significantly higher in the accessory basal, basal, lateral and cortical nuclei in AD and in all nuclei in DLB. The alpha-synuclein burden was significantly higher in all nuclei in both AD and DLB. Compared to AD alpha-synuclein burden was higher in all nuclei in DLB. There were no correlations between the distribution pattern of hyperphosphorylated tau-pathology, amyloid plaques and alpha-synuclein-positive structures, and choline acetyltransferase activity, except the lateral nucleus in DLB. In conclusion we found no relationship between the pattern of cholinergic deficits and the distribution pattern of lesions in the AC of patients with AD or DLB. Cholinergic deficits were more prominent in the nuclei of basolateral (BL) group in AD, whereas the nuclei of both BL and corticomedial groups were involved in DLB, which may be due to the involvement of both basal forebrain and brainstem cholinergic nuclei in the latter.

Effect of the μ Opioid on Excitatory and Inhibitory Synaptic Inputs to Periaqueductal Gray-Projecting Neurons in the Amygdala

Opioids are potent analgesics, but the sites of their action and cellular mechanisms are not fully understood. The central nucleus of the amygdala (CeA) is important for opioid analgesia through the projection to the periaquaductal gray (PAG). In this study, we examined the effects of mu opioid receptor stimulation on inhibitory and excitatory synaptic inputs to PAG-projecting CeA neurons retrogradely labeled with a fluorescent tracer injected into the ventrolateral PAG of rats. Whole-cell voltage-clamp recordings were performed on labeled CeA neurons in brain slices. The specific mu opioid receptor agonist, [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO, 1 microM), significantly reduced the frequency of miniature inhibitory postsynaptic currents (mIPSCs) without altering the amplitude and decay constant of mIPSCs in 47.6% (10 of 21) of cells tested. DAMGO also significantly decreased the peak amplitude of evoked IPSCs in 69% (9 of 13) of cells examined. However, DAMGO did not significantly alter the frequency of miniature excitatory postsynaptic currents (EPSCs) and the amplitude of evoked EPSCs in 69% (9 of 13) and 83% (10 of 12) of labeled cells, respectively. The IPSCs were blocked by the GABA(A) receptor antagonist bicuculline, whereas the EPSCs were largely abolished by the non-N-methyl-d-aspartate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. The immunoreactivity of mu opioid receptors was colocalized with synaptophysin, a presynaptic marker, in close appositions to labeled CeA neurons. These results suggest that activation of mu opioid receptors on presynaptic terminals primarily attenuates GABAergic synaptic inputs to PAG-projecting neurons in the CeA.

Neuropeptides in the cat amygdala

The distribution of seven neuropeptides was studied in the cat amygdala using an indirect immunoperoxidase technique. No labeling was found for luteinizing hormone-releasing hormone or beta-endorphin (1-27). Sparse alpha-melanocyte-stimulating hormone-immunoreactive fibers were found in the basomedial nucleus of the amygdala, whereas a low density of fibers containing alpha-neo-endorphin was observed in the anterior amygdaloid area. Neurotensin was observed in fibers of the anterior amygdaloid area (low density) and both the lateral (low density) and the medial part (moderate density) of the central nucleus. A low density of fibers containing neurokinin A was found in the anterior amygdaloid area, the basolateral nucleus, and the medial part of the central nucleus. A moderate density was observed in the basomedial nucleus and in the medial and cortical nuclei. Fibers containing somatostatin-28 (fragment 1-12) were observed in all the amygdaloid nuclei, whereas immunoreactive cell bodies were found in all the nuclei except in the medial part of the central nucleus and the medial nucleus. Perikarya containing neurokinin A were observed in the latter nucleus. The results point to a discrete distribution of peptidergic fibers in the cat amygdala, as well as the occurrence of neurons containing neurokinin A and somatostatin-28 (fragment 1-12). The distribution of the peptides studied in the cat is compared with the location of the same peptides in the amygdala of other species. The possible diencephalic origin of the peptidergic fibers is also discussed.

Neurotensin receptors in the human amygdaloid complex. Topographical and quantitative autoradiographic study

The distribution of high affinity 125I-neurotensin (NT) binding sites were investigated in the amygdaloid complex of adult humans by means of dry film and emulsion autoradiography. Autoradiograms were analysed quantitatively using [125I] standards and an image analyser system, and data obtained were converted to nCi of ligand bound per mg tissue. High densities of 125I-NT binding sites were found in the following amygdaloid structures the dorsal part of the accessory basal nucleus, the medial part of the cortical nucleus, the lateral subdivision of the central nucleus, the paralaminar nucleus, the amygdalohippocampal transition area and the rostral portions of the anterior amygdaloid area. The ventral part of the accessory basal nucleus, the intercalated cell groups and the remaining parts of the anterior amygdaloid area showed moderate density of NT binding sites, while the medial, basal and lateral amygdaloid nuclei, the lateral part of the cortical nucleus, the medial subdivision of the central nucleus, as well as the corticoamygdaloid transition area exhibited low densities of 125I-NT binding sites. At microscopic level, silver grains appeared more or less evenly distributed over both neuronal perikarya and the surrounding neuropil. In comparison to NT-immunoreactivity, NT receptors showed mismatching distribution throughout most parts of the amygdala, with the exception of the lateral subdivision of the central nucleus, where NT-immunoreactive perikarya and nerve fibers as well as 125I-NT binding sites were found in high density.

Effects of neurotensin on neurons in the rat central amygdaloid nucleus in vitro

The effects of neurotensin (NT) on neurons in the central amygdaloid nucleus (ACe) were investigated in rat brain slice preparations by adding the peptide to the perfusing medium. Of 115 ACe neurons, 69 cells (60%) showed excitatory responses and 10 cells (9%) showed inhibitory responses to application of NT. The excitatory response to NT was observed in a dose-dependent manner and the threshold concentration was approximately 3 x 10(-9) M. The excitatory effects of NT persisted under blockade of synaptic transmission. The NT fragment neurotensin 8-13 and the NT analogue neuromedin N showed effects similar to those of NT, whereas the NT fragment neurotensin 1-8 had no effect on ACe neurons. Of 43 neurons in the septal nucleus, 8 cells (19%) and 3 cells (7%) showed excitatory and inhibitory responses, respectively, to NT. The results suggest that NT exerts a potent excitatory effect on ACe neurons through a direct action on specific receptors, in which NT may play a role in amygdala-relevant functions.

Distribution of parvalbumin-immunoreactive cells and fibers in the human amygdaloid complex

The calcium-binding protein, parvalbumin, was localized immunohistochemically in the human amygdaloid complex. Neuronal cell bodies and fibers that are immunoreactive to parvalbumin were observed in most of the amygdaloid nuclei and cortical areas. Three types of immunoreactive aspiny neurons, ranging from small spherical cells (type 1) to large multipolar cells (type 2) and fusiform cells (type 3), were observed. The densities of the types of neurons that were parvalbumin-immunoreactive varied in the different regions of the amygdala. The highest densities of parvalbumin-immunoreactive neurons were observed in the lateral nucleus, in the magnocellular and intermediate divisions of the basal nucleus, in the magnocellular division of the accessory basal nucleus and in the amygdalohippocampal area. The regions containing the lowest density of parvalbumin-immunoreactive cells were the paralaminar nucleus, the parvicellular division of the basal nucleus, the central nucleus, the medial nucleus and the anterior cortical nucleus. In general, the distribution of immunoreactive fibers and terminals paralleled that of immunoreactive cells. Parvalbumin-immunoreactive varicose fibers formed basket-like plexi and cartridges around the unstained neurons, which suggests that parvalbumin is located in GABAergic basket cells and chandelier cells, respectively. The distribution of parvalbumin-immunoreactive profiles in the human amygdaloid complex was similar to, rather than different from that previously reported in the monkey amygdala (Pitkänen and Amaral [1993] J. Comp. Neurol. 331:14-36). This study provides baseline information about the organization of GABAergic inhibitory circuitries in the human amygdaloid complex.

Autoradiographic characterization of neurotensin receptors in the entorhinal cortex of schizophrenic patients and control subjects

Neurotensin, an endogenous peptide and putative neurotransmitter, exhibits a wide range of interactions with dopaminergic neurons and displays some actions akin to neuroleptics. Moreover, neurotensin receptors are abundant in specific layers of the entorhinal cortex where cytoarchitectural abnormalities have been reported in schizophrenia. We therefore examined the entorhinal cortex from postmortem specimens of five control patients and six schizophrenic patients for alterations in neurotensin receptor quantitation and distribution using receptor autoradiography. Specific 125I- neurotensin binding was concentrated in layer II cell clusters, with a 40% reduction in binding in the schizophrenic group (p < 0.05). Moderate binding was observed in both cohorts in deep layers V/VI, with negligible binding in the hippocampus. There was no statistical difference in quantitative neurotensin binding in other lamina of the entorhinal cortex of schizophrenics compared with controls. The characteristic laminar pattern of binding did not differ between cohorts. The reduction in neurotensin binding in schizophrenics is consistent with an increasing number of reports of structural abnormalities in the medial temporal lobe of schizophrenics in general and the entorhinal cortex in particular. Further studies are required to examine the evidence for neuroanatomic and neurochemical pathology in the entorhinal cortex.

Neurochemical development of the hippocampal region in the fetal rhesus monkey. II. Immunocytochemistry of peptides, calcium-binding proteins, DARPP-32, and monoamine innervation in the entorhinal cortex by the end of gestation

Material for the study came from one 126 day-old rhesus monkey fetus and two 3 day-old neonates. The immunocytochemical detection of somatostatin, neurotensin (NT), parvalbumin, calbindin D-28K, DARPP-32 as well as tyrosine hydroxylase (TH), dopamine-beta-hydroxylase and serotonin (5-HT), was carried out on serial cryostat sections of the entorhinal cortex. The authors reported in a previous paper the precocious differentiation of the entorhinal cortex in rhesus monkey fetuses and featured the conspicuous expression of calbindin D-28K, somatostatin, neurotensin, and the monoaminergic innervation during the first half of gestation. The present study shows distinct temporal profiles of neurochemical development during the second half of gestation: the dense neuropeptidergic innervation remained a constant feature; the three aminergic systems gradually increased in density; parvalbumin, unlike calbindin D-28K, was primarily expressed during the last quarter of gestation. Three other prominent features of the last quarter of gestation are illustrated: the refinement of the modular neurochemical organization of the lamina principalis externa, the delayed chemoanatomical development of the rhinal sulcus area, and the establishment of a distinct rostrocaudal pattern of neurochemical distribution. In correspondence with the cluster-like organization of the lamina principalis externa, the authors observed in the olfactory, rostral, and intermediate fields of the neonate monkey entorhinal cortex, a particular subset of pyramidal-shaped neurons: located in layer III, they were characterized by fasciculated apical dendrites ascending between the cellular islands of the discontinuous layer II and the coexpression of calbindin D-28K and DARPP-32. Besides, most of the other chemical systems displayed a distinct, area-specific, patchy distribution, except for the homogeneously distributed noradrenergic innervation. In the olfactory and rostral fields, TH positive dopaminergic fibers accumulated on the neuronal islands of layers II-III, and parvalbumin labeled fibers on those of layer III, whereas patches of 5-HT and NT-like reactive terminals were segregated between the cellular islands, overlapping the DARPP-32/calbindin D-28 K labeled dendritic bundles. At the opposite, in the intermediate field, 5-HT positive terminals overlapped the cellular islands of layer II and thin fascicles of dopaminergic fibers ran in the inter island spaces. The somatostatin-LIR innervation was apparently too dense to reveal a patchy distribution that existed at earlier developmental stages. In the caudal field, the patchy pattern was replaced by a predominant bilaminar type of distribution of NT, 5-HT, and TH-like positive afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Autoradiographic characterization of 125I-neurotensin binding sites in human entorhinal cortex

The laminar and rostro-caudal distribution of 125I-neurotensin binding sites is described in human entorhinal cortex using quantitative autoradiography. Specific binding was most prominent over the cell clusters of layer II of the entorhinal cortex throughout its rostro-caudal extent. Dense binding was also observed in the adjacent presubiculum and cortical amygdaloid transition area, whereas minimal binding was detected in the hippocampus and dentate gyrus. 125I-Neurotensin may serve as a selective probe for neurotensin receptor alterations and layer II-specific cytoarchitectural disturbances in the entorhinal cortex in neuropsychiatric diseases associated with abnormalities of the mesial temporal lobe.

Immunocytochemical distribution of peptidergic and cholinergic fibers in the human amygdala: their depletion in Alzheimer's disease and morphologic alteration in non-demented elderly with numerous senile plaques

As part of an ongoing investigation devoted to understanding the pathogenesis of senile plaques, we employed histochemical and immunocytochemical techniques to examine the distribution and cytologic features of acetylcholinesterase (AChE), choline acetyltransferase (ChAT), somatostatin (SOM), neurotensin (NT) and substance P (SP) containing fibers and neurons within the amygdala of: (1) patients with Alzheimer's disease (AD); (2) age-matched non-demented controls (NC); and (3) a group of non-demented cases, who upon postmortem neuropathologic examination exhibited sufficient numbers of senile plaques to be classified as AD. This latter group was referred to as high plaque non-demented (HPND). For every case, the distribution of immunolabeled fibers and neurons were determined for each transmitter throughout the various subnuclei of the amygdala. In addition, in the AD and HPND cases the topographic distribution of senile plaques was determined throughout the amygdala using thioflavine-S and Bielschowsky silver methods. In the amygdala, the distribution and density of senile plaques were not bound by conventional cytoarchitectural groupings but rather were most dense in the ventromedial regions of the amygdala with decreasing density in dorsal and lateral directions. Importantly, the density and distribution of senile plaques failed to correlate with the normal topography and/or density of the various peptidergic or cholinergic fibers within the amygdala. The finding that plaques do not correlate with the topographic distribution of any specific transmitter system suggests that plaques likely do not arise from the degeneration of a single neurotransmitter system (i.e., the cholinergic system). However, the finding that in AD a transmitter is most markedly depleted in regions of greatest plaque density, suggests certain constituents of the plaque (e.g. beta-amyloid) may be contributing to the degeneration of local fibers. The extent to which a transmitter was depleted in AD patients varied considerably among those four investigated with the cholinergic and NT systems displaying the most dramatic reductions, followed by SP and SOM. Despite these differential reductions in fiber density, all four neurotransmitters were found localized within dystrophic neurites and in most instances these dystrophic neurites were associated with thioflavine-positive senile plaques. In contrast to the AD cases, the HPND cases were characterized by no significant reductions in immunolabeled fibers, although immunostained dystrophic neurites were very prevalent in the HPND cases. These data suggest that dystrophic neurites occur very early in the disease process and likely precede the actual loss of fibers when or if it occurs.(ABSTRACT TRUNCATED AT 400 WORDS)

Galanin immunoreactivity within the primate basal forebrain: evolutionary change between monkeys and apes

Galanin immunoreactivity (GAL-ir) is differentially expressed within the basal forebrain of monkeys and humans. Most monkey magnocellular basal forebrain neurons colocalize GAL-ir. In contrast, virtually no human magnocellular basal forebrain neurons express GAL-ir. Rather, an extrinsic galaninergic fiber plexus innervates these neurons in humans. The present study examined the expression of GAL-ir within the basal forebrain of apes to establish the phylogenetic level at which this transformation occurs. The staining patterns of GAL-ir within the basal forebrain of both lesser (gibbons) and great (chimpanzee and gorilla) apes were compared to that previously observed within monkeys and humans. All apes displayed a pattern of basal forebrain GAL-ir indistinguishable from humans. GAL-ir was not expressed within ape basal forebrain magnocellular neurons as seen in monkeys. Rather like humans, a dense collection of GAL-ir fibers was seen in close apposition to magnocellular perikarya. In addition, a few GAL-ir parvicellular neurons were scattered within the ape basal forebrain. These data indicate that the evolutionary change in the expression of GAL-ir within the primate basal forebrain occurs at the branch point of monkeys and apes.

Evidence that transmitter-containing dystrophic neurites precede those containing paired helical filaments within senile plaques in the entorhinal cortex of nondemented elderly and Alzheimer's disease patients

Within the amygdala of elderly subjects and patients with Alzheimer's disease (AD), we recently found evidence suggesting amyloid beta-protein (A beta P) deposition occurs before the appearance of dystrophic neurites. Moreover, these data suggested dystrophic neurites initially lack evidence of cytoskeletal pathology although with time and further maturation, the dystrophic neurites display an altered cytoskeleton as evidenced by their immunoreactivity to Alz-50 and paired-helical filaments (PHF). These findings are of particular relevance to our understanding of the sequence of pathologic events in AD and thus it has become important to determine whether these events are unique to the amygdala or are representative of a more general pattern which can be found throughout the brain. Using a battery of antibodies to markers that are characteristic of AD pathology (i.e., A beta P, PHF, and Alz-50), three peptidergic neurotransmitters (neurotensin, somatostatin, and substance P), and one neurotransmitter biosynthetic enzyme (choline acetyltransferase), we examined the entorhinal cortex (EC) of three groups of subjects (AD, normal elderly, and a group of nondemented elderly with numerous senile plaques). The EC was studied, in part, because it is well recognized as a brain region displaying severe and, most importantly, early pathologic changes. Like the amygdala, we found evidence that amyloid beta-protein immunoreactive (A beta P-IR) and thioflavine-S-positive senile plaques occur within the EC prior to the appearance of transmitter-, Alz-50-, or PHF-immunoreactive dystrophic neurites. We also observed transmitter-immunoreactive dystrophic neurites in the absence of Alz-50 or PHF-immunolabeled dystrophic neurites and transmitter- and Alz-50-IR dystrophic neurites in the absence of those containing PHF. Collectively, these findings were similar to those seen within the amygdala and thus reinforced the concept that A beta P deposition is the primary event in plaque pathology, and this deposition is subsequently followed by the appearance of dystrophic neurites which retain their transmitter phenotype yet lack an altered cytoskeleton. With time, these dystrophic neurites develop cytoskeletal alterations and become immunoreactive to Alz-50 and PHF.

Evidence that transmitter-containing dystrophic neurites precede paired helical filament and Alz-50 formation within senile plaques in the amygdala of nondemented elderly and patients with Alzheimer's disease

Immunocytochemical techniques were employed to examine the temporal ordering whereby amyloid beta-protein (A beta P) and neuronal elements collectively come together to form senile plaques in Alzheimer's disease (AD). Specifically, we addressed three questions: (1) whether A beta P deposition precedes or follows neuritic changes; (2) whether paired helical filament (PHF) formation is an early or late event in the genesis of the dystrophic neurites which participate in plaque formation; and (3) whether the density of senile plaques displays any relationship with the prevalence of PHF or Alz-50 containing neurons. To address these questions we studied the amygdala from a group of patients with AD, a group of nondemented age-matched individuals exhibiting a sufficient number of senile plaques to be classified by neuropathological criteria as AD, and a group of age-matched controls without AD pathology. Amyloid-bearing plaques were demonstrated by A beta P immunolabeling and thioflavine-S staining. Neuritic changes in the form of dystrophic neurites were observed with the aid of antibodies against PHF, Alz-50, as well as antibodies against several neuropeptides (i.e., substance P, somatostatin, and neurotensin) and the acetylcholine biosynthetic enzyme, choline acetyltransferase. By using a graded range of pathologic changes both within and across the patient population to provide us with a means of evaluating plaque deposition from its earliest to most advanced stages of development, we observed in patients and/or regions of the amygdala displaying a mild degree of pathologic change A beta P deposition in the absence of any neuritic changes. With increasing density of A beta P, however, we began to observe dystrophic neurites within plaques. In regions of relatively few plaques, the dystrophic neurites were immunolabeled only with antibodies against the various neurotransmitters and they lacked evidence of cytoskeletal pathology (i.e., Alz-50 or PHF). Only as the density of A beta P increased further within a region, were dystrophic neurites observed that exhibited Alz-50 or PHF. In no instance did we observe a relationship between the density of A beta P deposition and the density of Alz-50 or PHF-immunoreactive neurons. Collectively, our data suggest that the deposition of A beta P is an early pathologic event in senile plaque formation. Thereafter, swollen neurites can be seen in the vicinity of A beta P. This early neuritic response, which can first be visualized by immunolabeling for one or another transmitter substance, is followed by alterations in the cytoskeleton as recognized initially by antibodies to Alz-50 and subsequently by the presence of PHF.

Alzheimer's disease-like dystrophic neurites characteristically associated with senile plaques are not found within other neurodegenerative diseases unless amyloid beta-protein deposition is present

Swollen, bulbous-shaped (dystrophic) neurites are a common pathologic feature of Alzheimer's disease (AD) and represent one of the most abundant neuritic abnormalities within the brains of patients with this disease. In the present study, we sought to determine whether the dystrophic neurites which are observed in association with senile plaques are unique to AD or whether they are characteristic of a more generalized process of neuritic and/or neuronal degeneration which can be observed in other neurodegenerative diseases. To accomplish this, we examined post-mortem brain material from patients with AD, Parkinson's disease (PD), Parkinson's disease with associated AD, Parkinson's disease with dementia yet without AD pathology, Huntington's disease (HD), Pick's disease and normal age-matched controls (NC). Using a battery of antibodies to amyloid beta-protein (A beta P), paired-helical filaments (PHF), tyrosine hydroxylase, substance P, neurotensin, and somatostatin we found that immunolabeled dystrophic neurites of the type characteristically observed in AD, were seen only in cases and in brain regions where A beta P deposition was present. More specifically, brain areas known to display severe afferent and/or local degenerative changes such as the caudate and putamen in all three PD groups, the caudate in the HD cases, and the temporal cortex in the HD and Pick's cases were conspicuously free of these swollen neurites unless A beta P deposition was also present.(ABSTRACT TRUNCATED AT 250 WORDS)