Elevation of neuropeptide Y (NPY) in substantia innominata in Alzheimer's type dementia

The Role of Neuropeptide Y in the Nucleus Accumbens

Neuropeptide Y (NPY), an abundant peptide in the central nervous system, is expressed in neurons of various regions throughout the brain. The physiological and behavioral effects of NPY are mainly mediated through Y1, Y2, and Y5 receptor subtypes, which are expressed in regions regulating food intake, fear and anxiety, learning and memory, depression, and posttraumatic stress. In particular, the nucleus accumbens (NAc) has one of the highest NPY concentrations in the brain. In this review, we summarize the role of NPY in the NAc. NPY is expressed principally in medium-sized aspiny neurons, and numerous NPY immunoreactive fibers are observed in the NAc. Alterations in NPY expression under certain conditions through intra-NAc injections of NPY or receptor agonists/antagonists revealed NPY to be involved in the characteristic functions of the NAc, such as alcohol intake and drug addiction. In addition, control of mesolimbic dopaminergic release via NPY receptors may take part in these functions. NPY in the NAc also participates in fat intake and emotional behavior. Accumbal NPY neurons and fibers may exert physiological and pathophysiological actions partly through neuroendocrine mechanisms and the autonomic nervous system.

The Role of Chronic Inflammatory Bone and Joint Disorders in the Pathogenesis and Progression of Alzheimer's Disease

Late-onset Alzheimer's Disease (LOAD) is a devastating neurodegenerative disorder that causes significant cognitive debilitation in tens of millions of patients worldwide. Throughout disease progression, abnormal secretase activity results in the aberrant cleavage and subsequent aggregation of neurotoxic Aβ plaques in the cerebral extracellular space and hyperphosphorylation and destabilization of structural tau proteins surrounding neuronal microtubules. Both pathologies ultimately incite the propagation of a disease-associated subset of microglia-the principle immune cells of the brain-characterized by preferentially pro-inflammatory cytokine secretion and inhibited AD substrate uptake capacity, which further contribute to neuronal degeneration. For decades, chronic neuroinflammation has been identified as one of the cardinal pathophysiological driving features of AD; however, despite a number of works postulating the underlying mechanisms of inflammation-mediated neurodegeneration, its pathogenesis and relation to the inception of cognitive impairment remain obscure. Moreover, the limited clinical success of treatments targeting specific pathological features in the central nervous system (CNS) illustrates the need to investigate alternative, more holistic approaches for ameliorating AD outcomes. Accumulating evidence suggests significant interplay between peripheral immune activity and blood-brain barrier permeability, microglial activation and proliferation, and AD-related cognitive decline. In this work, we review a narrow but significant subset of chronic peripheral inflammatory conditions, describe how these pathologies are associated with the preponderance of neuroinflammation, and posit that we may exploit peripheral immune processes to design interventional, preventative therapies for LOAD. We then provide a comprehensive overview of notable treatment paradigms that have demonstrated considerable merit toward treating these disorders.

Synaptic plasticity modulation by circulating peptides and metaplasticity: Involvement in Alzheimer's disease

Synaptic plasticity is a cellular process involved in learning and memory whose alteration in its two main forms (Long Term Depression (LTD) and Long Term Potentiation (LTP)), is observed in most brain pathologies, including neurodegenerative disorders such as Alzheimer's disease (AD). In humans, AD is associated at the cellular level with neuropathological lesions composed of extracellular deposits of β-amyloid (Aβ) protein aggregates and intracellular neurofibrillary tangles, cellular loss, neuroinflammation and a general brain homeostasis dysregulation. Thus, a dramatic synaptic environment perturbation is observed in AD patients, involving changes in brain neuropeptides, cytokines, growth factors or chemokines concentration and diffusion. Studies performed in animal models demonstrate that these circulating peptides strongly affect synaptic functions and in particular synaptic plasticity. Besides this neuromodulatory action of circulating peptides, other synaptic plasticity regulation mechanisms such as metaplasticity are altered in AD animal models. Here, we will review new insights into the study of synaptic plasticity regulatory/modulatory mechanisms which could influence the process of synaptic plasticity in the context of AD with a particular attention to the role of metaplasticity and peptide dependent neuromodulation.

A pool of Y2 neuropeptide Y receptors activated by modifiers of membrane sulfhydryl or cholesterol balance

The cloned guinea-pig Y2 neuropeptide Y (NPY) receptors expressed in Chinese hamster ovary (CHO) cells, as well as the Y2 receptors natively expressed in rat forebrain, are distributed in two populations. A smaller population that is readily accessed by agonist peptides on the surface of intact cells constitutes less than 30% of Y2 receptors detected in particulates after cell homogenization. A much larger fraction of cell surface Y2 sites can be activated by sulfhydryl modifiers. A fast and large activation of these masked or cryptic sites could be obtained with membrane-permeating, vicinal cysteine-bridging arsenical phenylarsine oxide. A lower activation is effected by N-ethylmaleimide, an alkylator that slowly penetrates lipid bilayers. The restricted-access alkylator, 2-[(trimethylammonium)ethyl]methanethiosulfonate, was not effective in unmasking these sites. Some of the hidden cell surface Y2 sites could be activated by polyene filipin III through complexing of membrane cholesterol. The results are consistent with the presence of a large Y2 reserve in a compartment that can be accessed by alteration of sulfhydryl balance or fluidity of the cell membrane, and by treatments that affect the anchoring and aggregation of membrane proteins.

Postnatal development of somatostatin- and neuropeptide Y-immunoreactive neurons in rat cerebral cortex: a double-labeling immunohistochemical study

The postnatal development of somatostatin (SOM)- and neuropeptide Y (NPY)-immunoreactive (ir) neurons was examined in rat cerebral cortex, while considering their coexistence in cortical neurons. Using double immunohistochemical staining for SOM and NPY with diaminobenzidine and benzidine dihydrochloride as chromogens, we subdivided immunoreactive cells into double-labeled SOM/NPY-, SOM only-, and NPY only-ir neurons. SOM/NPY- and SOM only-ir neurons were detectable even at the day of birth, in contrast on NPY only-ir cells which first appeared in most cortices from week two. The morphological features of double-labeled SOM/NPY neurons differed with those of SOM only- and NPY only-ir neurons. No apparent changes in the shape and size of single-labeled neurons occurred with age; throughout their postnatal life they were round and ovoid, had a thin rim of perinuclear cytoplasm, and short processes. However, the features of SOM/NPY-ir neurons were not consistent according to postnatal age; by day P7, these neurons showed immature features and they began to show more advanced neuronal characteristics by week P2, when they had a larger and more intensely-stain cytoplasm. In addition, their processes were longer, thicker and more complex than at earlier ages. At this age, SOM/NPY-ir somata were close to their near maximum size. From week P4, they became smaller and were lightly labeled. SOM/NPY-ir somata were larger than SOM only- and NYP only-ir somata at and after two weeks of age. The present results, showing different postnatal maturation patterns such as time of appearance and morphological features, raise the possibilities that double-labeled SOM/NPY and single-labeled immunoreactive neurons may be different populations regulated by different mechanisms in their development, and with different functional properties during development.

Role of glutamate receptor subtypes in the differential release of somatostatin, neuropeptide Y, and substance P in primary serum-free cultures of striatal neurons

The spiny and aspiny neuronal populations of the striatum display differential vulnerability to the toxic effects of glutamatergic agonists. Substance P-containing spiny neurons appear to be more vulnerable to NMDA-receptor-mediated toxicity and less susceptible to kainate toxicity than the somatostatin- and neuropeptide Y (NPY)-containing aspiny population. We studied whether selective glutamatergic agonists might have similar differential effects on neuropeptide release from the substance P- and somatostatin/NPY-containing neuronal populations. After collection of a baseline sample, striatal neurons in primary culture were treated with one of the following: phosphate-buffered saline, 56 mM potassium chloride (KCl), 100 microM N-methyl-D-aspartate (NMDA), 100 microM quisqualate, 100 microM kainate, or 100 microM glutamate. Baseline and treatment samples were measured by radioimmunoassay for somatostatin, NPY, and substance P. KCl and kainate provoked a selective release of somatostatin and NPY, whereas substance P measured in the same samples showed no response. By contrast, NMDA elicited a selective release of substance P without a similar increase of either somatostatin or NPY. Quisqualate evoked comparable responses in the three peptides. These results indicate that the glutamatergic regulation of somatostatin and NPY release from aspiny striatal neurons in primary culture is preferentially mediated by the kainate receptor, whereas substance P release is selectively mediated by the NMDA receptor. These findings suggest a preferential expression of functional kainate receptors on the aspiny somatostatin/NPY neurons and of NMDA receptors on the substance-P-containing spiny neurons.

Substantia innominata: a notion which impedes clinical-anatomical correlations in neuropsychiatric disorders

Comparative neuroanatomical investigations in primates and non-primates have helped disentangle the anatomy of the basal forebrain region known as the substantia innominata. The most striking aspect of this region is its subdivision into two major parts. This reflects the fundamental organizational scheme for this portion of the forebrain. According to this scheme, two major subcortical telencephalic structures, i.e. the striatopallidal complex and extended amygdala, form large diagonally oriented bands. The rostroventral extension of the pallidum accounts for a large part of the rostral subcommissural substantia innominata, while the sublenticular substantia innominata is primarily occupied by elements of the extended amygdala. Also dispersed across this region is the basal nucleus of Meynert, which is part of a more or less continuous collection of cholinergic and non-cholinergic corticopetal and thalamopetal cells, which stretches from the septum diagonal band rostrally to the caudal globus pallidus. The basal nucleus of Meynert is especially prominent in the primate, where it is sometimes inappropriately applied as a synonym for the substantia innominata, thereby tacitly ignoring the remaining components. In most mammals, the extended amygdala presents itself as a ring of neurons encircling the internal capsule and basal ganglia. The extended amygdala may be further subdivided, i.e. into the central extended amygdala (related to the central amygdaloid nucleus) and the medial extended amygdala (related to the medial amygdaloid nucleus), which generally form separate corridors both in the sublenticular region and along the supracapsular course of the stria terminalis. The extended amygdala is directly continuous with the caudomedial shell of the accumbens, and to some extent appears to merge with it. Together the accumbens shell and extended amygdala form an extensive forebrain continuum, which establishes specific neuronal circuits with the medial prefrontal-orbitofrontal cortex and medial temporal lobe. This continuum is particularly characterized by a prominent system of long intrinsic association fibers, and a variety of highly differentiated downstream projections to the hypothalamus and brainstem. The various components of the extended amygdala, together with the shell of the accumbens, are ideally structured to generate endocrine, autonomic and somatomotor aspects of emotional and motivational states. Behavioral observations support this proposition and demonstrate the relevance of these structures to a variety of functions, ranging from the various elements of the reproductive cycle to drug-seeking behavior. The neurochemical and connectional features common to the accumbens shell and the extended amygdala are especially relevant to understanding the etiology and treatment of neuropsychiatric disorders. This is discussed in general terms, and also in specific relation to the neurodevelopmental theory of schizophrenia and to the neurosurgical treatment of neuropsychiatric disorders.

Age-related change of neuropeptide Y-immunoreactive neurons in the cerebral cortex of aged rats

Recent studies have explored certain changes with aging of neurons containing neuropeptides. The extent of loss in aged central nervous system (CNS) of neuronal cells containing neuropeptide Y (NPY) has not yet been established with certainty, and available data is often contradictory. Changes of NPY-containing neurons with aging in the cerebral cortex of aged rat were demonstrated by immunocytochemistry. A major loss of NPY-immunoreactive (ir) neurons in the aged rat brain was observed in the retrosplenial cortex, frontal cortex area 1 and 2, parietal cortex area 1 and 2, occipital cortex area 1 and 2, temporal cortex area 3, cingulate cortex and the hippocampus proper. A loss of NPY-ir neurons was observed mostly in layers V and VI; in addition, the number and length of dendritic branches appeared to be decreased and shortened in the age group. These results indicate the involvement of NPY-ir neurons in the aging process of cerebral cortex, and provide the first morphological evidence for the loss of NPY neurons in the cerebral cortex of aged rats.

Neuropeptide deficits in schizophrenia vs. Alzheimer's disease cerebral cortex

Neuropeptide concentrations were determined in the postmortem cerebral cortex from 19 cognitive-impaired schizophrenics, 4 normal elderly subjects, 4 multi-infarct dementia (MID) cases, and 13 Alzheimer's disease (AD) patients. Only AD patients met criteria for AD. The normal elderly and MID cases were combined into one control group. Somatostatin concentrations were reduced in both schizophrenia and AD. Neuropeptide Y concentrations were reduced only in schizophrenia, and corticotropin-releasing hormone concentrations were primarily reduced in AD. Concentrations of vasoactive intestinal polypeptide and cholecystokinin also were reduced in schizophrenia, although not as profoundly as somatostatin or neuropeptide Y. In AD, cholecystokinin and vasoactive intestinal peptide were unchanged. Neuropeptide deficits in schizophrenics were more pronounced in the temporal and frontal lobes than in the occipital lobe. The mechanisms underlying these deficits in schizophrenia and AD are likely distinct. In schizophrenia, a common neural element, perhaps the cerebral cortical gaba-aminobutyric acid (GABA)-containing neuron, may underlie these deficits.

Neuropeptide changes in cortical and deep gray structures in Alzheimer's disease

The alteration of certain neuropeptide levels is a dramatic and consistent finding in the brains of AD patients. Levels of SS, which is normally present in high concentrations in cerebral cortex /75/, are consistently decreased in the neocortex, hippocampus and CSF of AD patients. In addition, decreased levels of SS correlate regionally with the distribution of neurofibrillary tangles in AD /47/. Most available evidence suggests that the subset of SS-containing neurons which lack NADPH diaphorase may be relatively vulnerable to degeneration in AD. CRF is another neuropeptide with frequently observed changes in AD. Levels of CRF, which is normally present in low concentrations in cortical structures /75/, are decreased in the neocortex and hippocampus of AD patients. However, levels of CRF in the CSF of AD patients are not consistently reduced, but this is likely a reflection of the relatively low levels of CRF normally present in cerebral cortex. Studies of deep gray structures in AD brains reveal elevated levels of GAL in the nucleus basalis. The ability of GAL to inhibit cholinergic neurotransmission has generated considerable interest, since degeneration of cholinergic neurons in the basal forebrain consistently occurs in AD. In addition, the presence of NADPH diaphorase in GAL-containing neurons may underlie the relative resistance of these neurons to degeneration. From the aforementioned studies, it appears that the neurons which are relatively resistant to neurodegeneration in AD contain NADPH diaphorase. It is hypothesized that the presence of NADPH diaphorase protects these neurons from neurotoxicity mediated by glutamate or nitric oxide. Although one recent study /147/ has reported an elevation of the microtubule-associated protein tau in the CSF of AD patients (and this could become a useful antemortem diagnostic tool for AD), no similar CSF abnormality has been found for any of the neuropeptides. Thus, the measurement of CSF neuropeptide levels presently remains unhelpful in the diagnosis and treatment of AD. Future research on neuropeptides and their potential roles in the pathogenesis, diagnosis, and treatment of AD will likely involve further development of pharmacological modulators of neuropeptide systems, together with the further study of brain neuropeptidases.

Central nervous system pharmacology of neuropeptide Y

Neuropeptide Y (NPY) is a 36-amino acid peptide belonging to the pancreatic polypeptide family that has marked and diverse biological activity across species. NPY originally was isolated from mammalian brain tissue somewhat more than 10 years ago and, since that time, has been the subject of numerous scientific publications. NPY and its proposed three receptors (Y1, Y2 and Y3) are relatively abundant in and uniquely distributed throughout the brain and spinal cord. This review will highlight the results from a number of research-oriented studies that have examined how NPY is involved in CNS function and behavior, and how these studies may relate to the possible development of medicines, either NPY-like agonists or antagonists, directed towards the treatment of disorders such as anxiety, pain, hypertension, schizophrenia, memory dysfunction, abnormal eating behavior and depression.

Cortical and subcortical neuropeptides in Alzheimer's disease

Given the clinical features of AD, the severe atrophy of cerebral cortex that accompanies the disease, and the predominant cortical location of plaques and tangles, it is not surprising to find the most consistent changes in neuropeptides in this disease occurring in the cerebral cortex. The neuropeptide changes that have been reproducibly demonstrated in AD are reduced hippocampal and neocortical SS and CRF concentrations and a reduced CSF level of SS. In cerebral cortex, SS and CRF are found in GABAergic local circuit neurons in layers II, III, and VI. The function of these neurons is not well established, although these cells may act to integrate the flow of incoming and outgoing information in cerebral cortex. If this is true, then dysfunction of this integration could produce widespread failure of cerebrocortical function, resulting in the various neurobehavioral deficits seen in AD. The interpretation of neuropeptide changes in subcortical brain regions, either those that project to cortex, or those that are the efferent targets of cortical projections, is also uncertain. The observed neuropeptide abnormalities in these brain regions in AD are less consistent than are those seen in cerebral cortex. Perhaps the most intriguing result in these regions is the increases in galanin-immunoreactive terminals seen in the nucleus basalis of AD brains. Galanin has been shown to inhibit acetylcholine release and to impair memory function in rats (46,113).(ABSTRACT TRUNCATED AT 250 WORDS)

Widespread deficits in somatostatin but not neuropeptide Y concentrations in Alzheimer's disease cerebral cortex

Somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) were measured in the cerebral cortex of 49 patients with Alzheimer's disease (AD), and 9 elderly controls. Concentrations of SLI were lower in AD patients relative to controls in 9 of 10 cortical regions. In contrast, no significant differences in NPYLI concentrations between the two groups were observed in any of 10 regions. These studies suggest a dissociation between SLI deficits and NPYLI concentrations in the postmortem cerebral cortex of AD patients. The apparent sparing of NPYLI-containing neurons suggests that neuropeptide Y may be located within a separate group of neurons compared to somatostatin.

Short- and long-term effects of nucleus basalis magnocellularis lesions on cortical levels of somatostatin and its receptors in the rat

Cognitive and histological alterations in human Alzheimer's disease (AD) are correlated with selective neuronal loss in nucleus basalis of Meynert. In search of an animal model of AD-linked neurochemical deficits, we examined the effects of short- (2 weeks) and long- (3 and 6 months) term lesions of the nucleus basalis magnocellularis (NBM) on somatostatinergic parameters in rat forebrain. NBM lesions were performed by unilateral injection of ibotenic acid into the NBM. Cortical choline-acetyl transferase (ChAT) activity and acetylcholinesterase staining in the NBM remained significantly decreased ipsi- as compared to contralaterally up to 6 months after the placement of the lesion. Somatostatin (SRIF) content was increased by 120% in the ipsilateral frontal cortex 6 months post-lesion but not at shorter time intervals. Levels of neuropeptide Y (which is extensively co-localized with SRIF in the forebrain) were not significantly altered after unilateral NBM lesions at any time point. A 30% decrease in SRIF binding capacity as well as a marked reduction of SRIF inhibition of adenylate cyclase, indicative of a loss of functional SRIF receptors, was observed in ipsilateral versus contralateral frontal cortex on brain tissue homogenates after short-term unilateral NBM lesion. By film radioautography, the loss in SRIF binding sites was localized to both superficial and deep layers of the frontal cortex. This loss persisted up to 3 months but was no longer apparent after 6 months due to a decrease in SRIF binding capacity on the contralateral side.

Immunohistochemical and chromatographic identification of peptides derived from proneuropeptide Y in the human frontal cortex

Proneuropeptide Y (proNPY) is posttranslationally processed to NPY(1-36)amide and the C-terminal flanking peptide of NPY (CPON). Antisera directed against the N-terminal part of NPY, CPON, or CysNPY(32-36)amide were used to identify peptide fragments processed from proNPY in biopsies of human frontal cortical specimens obtained from patients who underwent surgical treatment of profound cerebral tumors. Gel filtration and radioimmunoassays of human cortical extracts revealed that the NPY immunoreactivity was found only as NPY(1-36)amide, indicating that all NPY is present in an amidated form. In contrast, no intact proNPY was identified. NPY/CPON-immunoreactive neurons were observed to be nonspiny with long axonal processes mostly orientated longitudinally in the direction of the superficial layers. Bundles of immunoreactive fibers in the underlying white matter were orientated toward superficial layers of the neocortex, indicating a subcortical origin of some NPY/CPON nerve fibers. Axonal terminals were distributed throughout the neocortex, with highest numbers observed in layer I. Some fibers penetrated from the superficial layer I into the overlying pial surface. Many fibers were also observed in proximity to intracortical blood vessels, and some of these fibers originated from the cortical neurons, indicating that NPY could play a role as an intracortical autoregulator of the tonus of cerebral arterioles. Together these results indicate that NPY(1-36)amide and CPON are present in intracortical neurons as two independent molecules and that NPY may be involved in synaptic processes and regulation of blood flow in the human brain.

The role of cortical connectivity in Alzheimer's disease pathogenesis: a review and model system

Here we review current evidence in support of the cortical disconnection/cortical connectivity model of Alzheimer disease (AD) pathogenesis, a model which predicts that one of the first events in AD is damage to the entorhinal cortex and/or subiculum resulting in the disconnection of the hippocampal formation and neocortex, and the subsequent progression of the disease in a stepwise fashion along cortico-cortical connections. Much of the evidence for this model has been obtained from studies involving the limbic system where investigators have demonstrated a precise correspondence between established patterns of connectivity and the degenerative changes associated with AD. In addition, some studies of the distribution of neuritic plaques (NP) and neuro-fibrillary tangles (NFT) in the neocortex and subcortical structures have yielded corroborative data. The validity of the cortical disconnection/connectivity model in the neocortex remains to be established or refuted. We propose that testing of this model can be accomplished with systematic studies of the laminar and regional distribution of NP and NFT in a series of sequentially interconnected cytoarchitectural regions that also form part of two functional hierarchies--the paralimbic and occipitotemporal visual systems. To adequately control for variation between brains affected by AD, it is imperative that such studies be conducted in a large but varied population of AD cases exhibiting differences in several variables, including clinical and/or neuropathological severity of the disease, temporal duration of the disease, and clinical/neuropsychological profile. We believe that further understanding of the relationship between characteristic AD pathology and intrinsic anatomico-functional circuits will contribute not only to our comprehension of AD pathogenesis but also to our general knowledge of the human brain.

Cerebrospinal fluid norepinephrine, 3-methoxy-4-hydroxyphenylglycol and neuropeptide Y levels in Parkinson's disease, multiple system atrophy and dementia of the Alzheimer type

Neuropeptide Y, one of the most abundant polypeptides within the nervous system, is co-stored with catecholamines, especially norepinephrine (NE), thus suggesting its possible involvement in pathologies characterized by a noradrenergic impairment. In Parkinson's disease (PD), as well as in multiple system atrophy (MSA), a central noradrenergic deficit has been demonstrated, and in the dementia of Alzheimer type (DAT) an impaired noradrenergic transmission has been postulated. In this study we determined CSF NE and MHPG levels in 29 PD, 15 MSA, 22 DAT patients and in 36 controls, while CSF NPY-immunoreactivity (NPY-ir) levels were measured in 10 PD, 7 MSA, 10 DAT patients and 20 controls. PD, MSA, and DAT patients showed a significant reduction in CSF NPY-ir and NE levels compared with controls, while CSF MHPG levels resulted in a reduction in only the MSA group. Furthermore, an inverse correlation between either NE or MHPG levels and the duration of the orthostatic hypotension was found in MSA patients while for DAT patients the MHPG levels were directly correlated to the severity of cognitive impairment, and inversely to the duration of illness.

NADPH-diaphorase-positive cell populations in the human amygdala and temporal cortex: neuroanatomy, peptidergic characteristics and aspects of aging and Alzheimer's disease

Previous studies have shown that nerve cells containing NADPH-diaphorase (NADPH-d) are relatively resistant to various damaging processes. NADPH-d has been found to be colocalized with somatostatin (SOM) and neuropeptide Y (NPY) in neuronal populations of several forebrain regions. We have investigated the anatomical distribution, morphology and cell sizes of NADPH-d neurons in amygdala and temporal cortex in Alzheimer's disease (AD) compared to controls of different age. NADPH-d cells and fibers were present in layers II-VI of the cortex and in the white matter below the cortical mantle. In the amygdaloid complex, NADPH-d cells and processes were observed in almost all subnuclei. In the amygdala of aged controls, only insignificant atrophic alterations of NADPH-d neurons and fibers were seen. In AD, a moderate, but significant shift towards an increased number of medium-to small-sized neurons was measured in amygdala and cortex, indicating cell shrinkage during the course of the disease. However, there were no differences when comparing NADPH-d staining in amygdaloid subregions in AD cases that contained numerous neuritic plaques (i.e., accessory basal nucleus) with areas that were relatively free of lesions (i.e., lateral nucleus). Analysis of cell size of SOM- and NPY-immunoreactive cells revealed only slight atrophic changes during aging. In AD, however, a significant atrophy of somatostatin neurons in temporal cortex was found, whereas no further cell shrinkage was noted for NPY as compared to aged controls. Colocalization tests demonstrated a large overlap between NPY, SOM and NADPH-d in the amygdala, whereas a subpopulation of cortical SOM neurons, predominantly localized in upper layers, showed a lack of NADPH-d. Our findings of a relative stability of a selective subclass of neurons during aging and AD support the hypothesis that cellular pathology may affect only specific neuronal populations while others might be spared.

The bed nucleus-amygdala continuum in human and monkey

The cytoarchitecture and distributions of seven neuropeptides were examined in the the bed nucleus of the stria terminalis (BST), substantia innominata (SI), and central and medial nuclei of the amygdala of human and monkey to determine whether neurons of these regions form an anatomical continuum in primate brain. The BST and centromedial amygdala have common cyto- and chemo-architectonic characteristics, and these regions are components of a distinct neuronal complex. This neuronal continuum extends dorsally, with the stria terminalis, from the BST and merges with the amygdala; it extends ventrally from the BST through the SI to the centromedial amygdala. The cytoarchitectonics of the BST-amygdala complex are heterogeneous and compartmental. The BST is parcellated broadly into anterior, lateral, medial, ventral, supracapsular, and sublenticular divisions. The central and medial nuclei of the amygdala are also parcellated into several subdivisions. Neurons of central and medial nuclei of the amygdala are similar to neurons in the lateral and medial divisions of the BST, respectively. Neurons in the SI form cellular bridges between the BST and amygdala. The BST, SI, and amygdala share several neuropeptide transmitters, and patterns of peptide immunoreactivity parallel cytological findings. Specific chemoarchitectonic zones were delineated by perikaryal, peridendritic/perisomatic, axonal, and terminal immunoreactivities. The results of this investigation demonstrate that there is a neuronal continuity between the BST and amygdala and that the BST-amygdala complex is prominent and discretely compartmental in forebrains of human and monkey.

Neuropeptide Y: an overview of central distribution, functional aspects, and possible involvement in neuropsychiatric illnesses

Neuropeptide Y (NPY) was first discovered and characterized as a 36-amino-acid peptide neurotransmitter in 1982. It is widely distributed in the central nervous system, with particularly high concentrations within several limbic and cortical regions. A number of co-localizations with other neuromessengers such as noradrenaline, somatostatin, and gamma-aminobutyric acid have been demonstrated. A large number of physiological and pharmacological actions of NPY have been suggested. Recent clinical data also suggest the involvement of NPY in several neuropsychiatric illnesses, particularly in depressive and anxiety states. This article gives a comprehensive review of central distribution of NPY and its receptors, co-localizations and interactions with other neuromessengers, genetic aspects, pharmacological and physiological actions, influence on neuroendocrine functions, and possible involvement in various neuropsychiatric illnesses.

Neuropeptides and Alzheimer's disease

Because of their putative roles as neurotransmitters, neuromodulators, and neuroregulators in the central nervous system, neuropeptides have been the focus of considerable research over the past two decades. There is evidence that alterations in the synaptic availability of particular neuropeptides occur in certain neuropsychiatric disorders, such as schizophrenia and affective disorders. Alzheimer's disease is the most common neurodegenerative disorder, affecting a sizable proportion of our aging population. Alzheimer's disease is characterized by the presence of neurofibrillary tangles and senile plaques in the central nervous system. Postmortem studies have provided evidence that several neuropeptide-containing neurons are pathologically altered in this disorder. The purpose of this article is to describe recent advances in neuropeptide biology with a focus on the role of neuropeptides in the pathogenesis of Alzheimer's disease.

Neuropeptide Y receptor binding sites in human brain. Possible alteration in Alzheimer's disease

Neuropeptide Y (NPY) and peptide YY (PYY) receptor sites were studied in human brain using saturation binding experiments and receptor autoradiography. Additionally, the affinities and densities of [3H]NPY binding sites were compared in the temporal cortex, hippocampus and putamen of patients dying from Alzheimer's disease (AD) and aged matched controls. High densities of [3H]NPY binding sites were found in the putamen (192 +/- 32 fmol/mg protein), followed by the hippocampus (165 +/- 42 fmol/mg protein) and temporal cortex (118 +/- 19 fmol/mg protein). Receptor autoradiography revealed that these sites were especially concentrated in certain layers of the hippocampus, laminae I and IV-V of the temporal cortex and the amygdalo-hippocampal area. No significant changes in [3H]NPY binding affinities were seen between the AD and aged-matched groups (Kd ranges: 2.5-6.8 nM). However, significant decreases in [3H]NPY receptor densities (Bmax) were found in temporal cortex (-43%) and hippocampus (-49%) in AD brains. No significant change in [3H]NPY Bmax values was found in the putamen. It is therefore possible that decreases in [3H]NPY receptor densities may be associated to the degenerative process taking place in certain brain regions in AD, although further work will be necessary to confirm this hypothesis. Part of this work was presented at the 17th Annual Meeting of the Society for Neuroscience.

Neuropeptide Y: localization in the central nervous system and neuroendocrine functions

Neuropeptide Y (NPY) is a 36-amino acid peptide first isolated and characterized from porcine brain extracts. A number of immunocytochemical investigations have been conducted to determine the localization of NPY-containing neurons in various animal species including both vertebrates and invertebrates. These studies have established the widespread distribution of NPY in the brain and in sympathetic neurons. In the rat brain, a high density of immunoreactive cell bodies and fibers is observed in the cortex, caudate putamen and hippocampus. In the diencephalon, NPY-containing perikarya are mainly located in the arcuate nucleus of the hypothalamus; numerous fibers innervate the paraventricular and suprachiasmatic nuclei of the hypothalamus, as well as the paraventricular nucleus of the thalamus and the periaqueductal gray. At the electron microscope level, using the pre- and post-embedding immunoperoxidase techniques, NPY-like immunoreactivity has been observed in neuronal cell body dendrites and axonal processes. In nerve terminals of the hypothalamus, the product of the immunoreaction is associated with large dense core vesicles. In lower vertebrates, including amphibians and fish, neurons originating from the diencephalic (or telencephalic) region innervate the intermediate lobe of the pituitary where a dense network of immunoreactive fibers has been detected. At the ultrastructural level, positive endings have been observed in direct contact with pituitary melanotrophs of frog and dogfish. These anatomical data suggest that NPY can act both as a neurotransmitter (or neuromodulator) and as a hypophysiotropic neurohormone. In the rat a few NPY-containing fibers are found in the internal zone of the median eminence and high concentrations of NPY-like immunoreactivity are detected in the hypothalamo-hypophyseal portal blood, suggesting that NPY may affect anterior pituitary hormone secretion. Intrajugular injection of NPY causes a marked inhibition of LH release but does not significantly affect other pituitary hormones. Passive immunoneutralization of endogenous NPY by specific NPY antibodies induces stimulation of LH release in female rats, suggesting that NPY could affect LH secretion at the pituitary level. However, NPY has no effect on LH release from cultured pituitary cells or hemipituitaries. In addition, autoradiographic studies show that sites for 125I-labeled Bolton-Hunter NPY or 125I-labeled PYY (2 specific ligands of NPY receptors) are not present in the adenohypophysis, while moderate concentrations of these binding sites are found in the neural lobe of the pituitary. It thus appears that the inhibitory effect of NPY on LH secretion must be mediated at the hypothalamic level.(ABSTRACT TRUNCATED AT 400 WORDS)

A quantitative assessment of somatostatin-like and neuropeptide Y-like immunostained cells in the frontal and temporal cortex of patients with Alzheimer's disease

Immunocytochemical studies utilizing radioimmunoassay and morphological techniques have provided conflicting evidence for the involvement of somatostatin and neuropeptide Y in Alzheimer's disease (AD). However, previous investigators have not considered the effects of cortical atrophy in AD tissue on their findings. This study reports the numbers of somatostatin-like (SLI) and neuropeptide Y-like immunoreactive (NPYLI) neuronal perikarya and the length of SLI and NPYLI immunoreactive fibres, with appropriate corrections for atrophy in 6 control and 6 AD cases. There were significantly fewer SLI neurones in AD in layers II + III combined from the temporal cortex, and fewer NPYLI neurones in layers V + VI in both frontal and temporal cortices. Using a randomized method to quantify immunostained fibre length in the neuropil, an analysis of variance revealed no significant differences in the mean SLI or NPYLI fibre length per cortical strip between control and AD groups in frontal or temporal cortex. However, using a second measure of fibre length by tracing the fibres attached to consecutive immunostained perikarya, there were significant reductions in the AD brains in the mean fibre length per cell in layers V + VI for SLI in the temporal cortex, and for NPYLI in the frontal cortex. This reduction in fibre length per individual cell was presumably masked by the large variation in the fibre length found between cases using the randomized approach. It was concluded that in order to evaluate the involvement of these neuropeptides in AD from any measurements of concentration, it is essential to include some compensation for the extent of cortical atrophy that occurs with the disease.

Peptides in the neocortex in Alzheimer's disease and ageing

Studies which have examined neuropeptides in Alzheimer's disease (AD) and normal ageing are reviewed. A marked specificity and selectivity is noted: most neuropeptides are normal, and the only two peptides consistently altered are somatostatin (SRIF) and corticotropin releasing hormone (CRH). Binding sites for CRH are increased in number in a reciprocal fashion to the reduction in CRH. These findings (1) provide evidence for selective vulnerability within the cortex in AD, (2) suggest that the primary site of pathology in AD may be cortical, and (3) indicate that the pathological process of AD is distinct from that of normal ageing.

Modulation of memory processing by neuropeptide Y varies with brain injection site

Neuropeptide Y (NPY) is a 36 amino acid peptide which was shown to enhance memory retention, recall and prevent amnesia induced by either scopolamine or anisomycin. In this study, we examined the effects of NPY administration into 6 areas of the mouse brain on memory retention for footshock avoidance training in a T-maze. NPY was injected into the rostral and caudal hippocampus, amygdala, caudate, septum and thalamus shortly after training. NPY improved retention when injected into the rostral portion of the hippocampus and septum, impaired retention in the caudal portion of the hippocampus and amygdala and had no effect in the thalamus and caudate. NPY was ineffective at either improving or impairing retention when injected 24 h after training, thus demonstrating that the effects of NPY on retention were time-dependent and not due to proactive effects on retention test performance per se. In addition, NPY had no effect on retention when injected into overlying cortical areas. NPY antibody impaired retention when administered into the rostral hippocampus and septum; it improved retention in the caudal hippocampus and amygdala. Thus NPY antibody had the opposite effect to that of NPY on memory retention suggesting that NPY has a physiological role as a modulator of memory processing within specific anatomical areas of the central nervous system.

Subpopulations of somatostatin 28-immunoreactive neurons display different vulnerability in senile dementia of the Alzheimer type

We tested whether the vulnerability of somatostatin (SST) neurons in senile dementia of the Alzheimer type (SDAT) depended upon their co-localization with neuropeptide Y (NPY). Density estimates of SST28- and NPY-immunoreactive neurons and percentage of double-labeled SST-NPY neurons were obtained in the cortex (areas 9 and 25) and the bed nucleus of stria terminalis (BST), in 6 SDAT and 5 control cases. Counts of senile plaques (SP) and neurofibrillary tangles (NFT) were done on thioflavin S stains. In both cortical areas, a decrease in the density of SST28-IR neurons was found in SDAT cases (-60% in area 25 and -80% in area 9), whereas density of NPY-IR neurons was unchanged. Accordingly, the proportion of single-labeled SST neurons decreased; this decrease was significantly correlated with SP (r = -0.89, P less than 0.001). We conclude that single SST-IR neurons, in cortical layers II-III, and V, are preferentially lost relative to co-localized SST-NPY neurons. In the BST, no significant reduction of SST-IR, NPY-IR neurons nor of the percentage of single labeled SST neurons was found, despite the presence of SP. Thus one subpopulation of SST neurons, defined by associated neurochemical characters (not co-localized with NPY nor with NADPH diaphorase) and by topography (cortical layers III and V) appears to be particularly vulnerable in SDAT. The potential importance of their position in neural circuitry is emphasized.

Regional distribution of neuropeptide Y and its receptor in the porcine central nervous system

The regional distribution of neuropeptide Y (NPY) immunoreactivity and receptor binding was studied in the porcine CNS. The highest amounts of immunoreactive NPY were found in the hypothalamus, septum pellucidum, gyrus cinguli, cortex frontalis, parietalis, and piriformis, corpus amygdaloideum, and bulbus olfactorius (200-1,000 pmol/g wet weight). In the cortex temporalis and occipitalis, striatum, hippocampus, tractus olfactorius, corpus mamillare, thalamus, and globus pallidus, the NPY content was 50-200 pmol/g wet weight, whereas the striatum, colliculi, substantia nigra, cerebellum, pons, medulla oblongata, and medulla spinalis contained less than 50 pmol/g wet weight. The receptor binding of NPY was highest in the hippocampus, corpus fornicis, corpus amygdaloideum, nucleus accumbens, and neurohypophysis, with a range of 1.0-5.87 pmol/mg of protein. Intermediate binding (0.5-1.0 pmol/mg of protein) was found in the septum pellucidum, columna fornicis, corpus mamillare, cortex piriformis, gyrus cinguli, striatum, substantia grisea centralis, substantia nigra, and cerebellum. In the corpus callosum, basal ganglia, corpus pineale, colliculi, corpus geniculatum mediale, nucleus ruber, pons, medulla oblongata, and medulla spinalis, receptor binding of NPY was detectable but less than 0.5 pmol/mg of protein. No binding was observed in the bulbus and tractus olfactorius and adenohypophysis. In conclusion, immunoreactive NPY and its receptors are widespread in the porcine CNS, with predominant location in the limbic system, olfactory system, hypothalamoneurohypophysial tract, corpus striatum, and cerebral cortex.

Distribution of neuropeptide Y-containing perikarya and axons in various neocortical areas in the macaque monkey

The laminar and areal distribution of neuropeptide Y (NPY)-containing perikarya and their processes was analyzed immunocytochemically in Brodmann's neocortical areas 17, 18, 7, 22, 3, 4, 24, and 9 (Walker's area 46) in seven macaque monkeys. Most NPY-containing cells are distributed in two broad bands in layers II-III and V-VI in all areas; relatively few cells can be found in layer I and virtually none in layer IV. Numerous NPY-containing cells are situated in the white matter immediately subjacent to the cortical gray. Severalfold regional and individual differences in the density of NPY-positive somata were found in supra- and infragranular layers. However, the interareal variations in the density of NPY-containing somata do not conform to a universal pattern, because of either individual variability or inherent difficulties in standardizing immunocytochemical labeling. In contrast, the laminar differences in the distribution of NPY-containing axons among cortical areas are consistent in all animals. In general, primary sensory and motor areas have a lesser density of NPY-containing axons than association and limbic areas. Within the general pattern, area-specific laminar segregation of NPY-containing axons occurs. The regional differences in the distribution of NPY-like immunoreactivity in the neocortex may reflect innate characteristics of local neuronal circuits serving specialized functions.

Multiple types of neuropeptide Y-containing neurons in primate neocortex

The avidin-biotin-peroxidase method was used at the light and electron microscopic levels to analyze neuropeptide Y (NPY)-containing neurons in the neocortex of six adult macaque monkeys. Regions studied included various sensory, motor, limbic, and association areas, designated as 17, 18, 7, 22, 3, 4, 6, 24, and 9 by Brodmann (Beiträge zur Histologischen Lokalisation der Grosshirnrinde. Leipzig: Barth, '06). Several types of NPY-containing neurons can be distinguished by their laminar location, by the size of their perikarya, and by the size, shape, and pattern of ramification of their processes: 1) layer I small local circuit neurons; 2) layer II granule cells; 3) aspiny stellate cells located in layers II-III and V-VI, with long, slender dendrites; 4) sparsely spiny stellate cells; 5) aspiny stellate cells with long, horizontally oriented dendrites, whose cell body is situated in layer VI; 6) Martinotti cells in areas 9, 7, and 24; and 7) multipolar neurons situated in the white matter subjacent to the cortical gray. The possibility of additional neuronal types containing NPY is suggested by labeled densely spinous dendrites in area 6 and recurving axons and axonal loops in the supragranular layers in areas 7 and 9. No NPY-containing neurons were found in layer IV of any area, except layers IVA and B of the visual cortex. Likewise, nonneuronal elements were not labeled. The regional differences in the distribution of some NPY-containing neuron types may reflect adaptations of local neuronal circuits for specialized functions.

Neuropeptide Y (NPY) and the central nervous system: distribution effects and possible relationship to neurological and psychiatric disorders

1. NPY is a 36 amino acid tyrosine-rich peptide. It is one of the most abundant and widely distributed neuropeptides known today within the central nervous system with particularly high concentrations in the hypothalamus and in several limbic regions. 2. NPY seems to coexist with other on neurotransmitters like somatostatin, galanin, GABA and the catecholamines noradrenaline and adrenaline in discrete brain regions. 3. NPY binding sites are widely distributed in the brain. However they do not always overlap with the distribution of NPY-like immunoreactivity. 4. NPY is suggested to be involved in a large number of neuroendocrine functions, stress responses, circadian rhythms, central autonomic functions, eating and drinking behaviour, and sexual and motor behaviour. 5. Psychotropic drugs and neurotoxins can alter the NPY concentrations in discrete brain regions. 6. It is possible that NPY is related to various neurological and psychiatric illnesses, like Huntington's chorea, Alzheimer's disease, Parkinson's disease, eating disorders, and major depressive illness.

Neurochemical characteristics of aluminum-induced neurofibrillary degeneration in rabbits

Aluminum-induced neurofibrillary degeneration in rabbits is known to affect particular populations of neurons. The neurotransmitter alterations which accompany aluminum neurofibrillary degeneration were examined in order to assess how closely they mimic those of Alzheimer's disease. There was a significant reduction in choline acetyltransferase activity in entorhinal cortex and hippocampus as well as significant reductions in cortical concentrations of serotonin and norepinephrine in the aluminum-treated rabbits. Significant reductions in glutamate, aspartate and taurine were found in frontoparietal and posterior parietal cortex. Concentrations of GABA were unchanged in cerebral cortex. Both substance P and cholecystokinin immunoreactivity were significantly reduced in entorhinal cortex but there were no significant changes in somatostatin, neuropeptide Y and vasoactive intestinal polypeptide. The five neuropeptides were unaffected in striatum, thalamus, cerebellum and brainstem. Neurochemical changes were found in the regions with the most neurofibrillary degeneration while regions with little or no neurofibrillary degeneration were unaffected. The reductions in choline acetyltransferase activity, serotinin and noradrenaline suggest that some neuronal populations preferentially affected in Alzheimer's disease are also affected by aluminum-induced neurofibrillary degeneration; however, the cortical somatostatin deficit which is a feature of Alzheimer's disease is not replicated in the aluminum model.

N-terminal ACTH fragments increase the CSF beta-EP content in Alzheimer type dementia

Eleven patients with presenile Alzheimer type dementia (ATD) were treated with N-terminal ACTH fragments for 14 days. No change in cognitive functions was observed during the treatment. A significant increase in CSF beta-endorphin (beta-EP) levels was found, while ACTH and beta-lipoprotein remain unaffected. The possibility that ACTH and its moieties could interfere with beta-EP activities in CNS is discussed.

Neuropeptides and neuropathology in the amygdala in Alzheimer's disease: relationship between somatostatin, neuropeptide Y and subregional distribution of neuritic plaques

This study examined the amygdaloid complex in Alzheimer's disease (AD). We compared the distribution and morphology of somatostatin (SOM-) and neuropeptide Y-immunoreactive (NPY-IR) neurons in the amygdala with the distribution of neuritic plaques (NP) and acetylcholinesterase (AChE) staining patterns in various subnuclei. We found that in AD, there was an increase in the number of small, atrophic neurons for both SOM and NPY, and subregional analysis revealed similar size reductions in all subnuclei. In contrast, the highest density of NP was found in the corticomedial nuclei and densest staining for AChE in the basal nucleus. Although NPY- and SOM-IR fibers were occasionally associated with NP, a dense, morphologically preserved peptidergic fiber-network was found in all areas including subnuclei with high numbers of NP. Our study indicates that atrophic SOM- and NPY-IR neurons are not correlated with the subregional distribution of NP or cholinesterase staining pattern of the amygdala, and suggests that alterations in SOM and NPY neurons are not characteristics of the primary pathogenic process that underlie the formation of NP or cholinergic cell loss in AD.

Neuropeptide Y-like immunoreactive neurons in the human olfactory bulb

Neuropeptide Y-like (NPY) immunoreactivity was localized in the adult human olfactory bulb by the unlabeled antibody enzyme (peroxidase anti-peroxidase; PAP) technique in vibratome sections. The majority of NPY-immunoreactive somata was localized in the white matter surrounding the anterior olfactory nucleus. Immunoreactive neurons were less numerous within the anterior olfactory nucleus and within the olfactory bulb layers. NPY-immunoreactive fibres were present in the white matter, the anterior olfactory nucleus, and in the olfactory bulb layers. Fibres within the white matter were generally aligned in a straight path parallel to the long axis of the olfactory bulb and tract. Fibres within the anterior olfactory nucleus showed no clear orientation and displayed numerous branching points. Coiled plexus of NPY-immunoreactive fibres were present in the glomerular layer of the olfactory bulb. Additional characteristics of the NPY-immunoreactive neurons were studied after decolouring the chromogen and restaining the sections with aldehydefuchsin to demonstrate the presence of lipofuscin granules and also with gallocyanin chrome alum to stain the Nissl substance. This analysis showed that the neurons belong to the class of non-pigmented nerve cells.

Neuropeptide Y stimulates inositol phospholipid hydrolysis in rat brain miniprisms

Neuropeptide Y (NPY) stimulates the hydrolysis of inositol phospholipid in rat brain miniprisms. The stimulation was two-fold in the frontal cortex and in the hippocampus, and 1.5-fold in the striatum. NPY produced no significant effects on basal inositol monophosphate levels in hypothalamic miniprisms. However, those basal levels were much higher than in the other brain regions.

Cortical somatostatin, neuropeptide Y, and NADPH diaphorase neurons: normal anatomy and alterations in Alzheimer's disease

Somatostatin and neuropeptide Y are two neuropeptides that are of particular interest in Alzheimer's disease because they are reported to be depleted in cerebral cortex. In the present study we examined somatostatin, neuropeptide Y, and nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase neurons in nine cortical regions in both normal and Alzheimer's disease brains. These three neurochemical markers show a high degree of co-localization (greater than 90%) in nonpyramidal neurons that are primarily distributed in cortical layers II-III, V-VI, and, most prominently, in infracortical white matter. The highest cell density was in temporal and parietal association cortex. The major morphological abnormality in Alzheimer's disease brains was a marked pruning and distortion of fiber plexuses with an apparent reduction in fiber density. In contrast, perikaryal density was preserved except for a reduction in parietal association cortex. Approximately 10 to 15% of senile plaques in the inferior temporal gyrus contained abnormal neurites. Additional abnormal collections of neurites without plaque cores were frequently found in layers II-III and V-VI. Neuropeptide Y and somatostatin were co-localized in abnormal neurites, suggesting an origin from local intrinsic neurons in which the two peptides are co-localized. Double immunofluorescence staining for both tau protein, a major antigenic component of paired helical filaments, and either somatostatin or neuropeptide Y showed that these neurons do not contain tau-immunoreactive neurofibrillary tangles. The morphological correlate of reduced somatostatin and neuropeptide Y content in Alzheimer's disease brain therefore appears to be a distortion and reduction in fiber plexuses. In addition, it is apparent that these neurons can develop widespread morphological abnormalities in the absence of neurofibrillary tangle formation.

Somatostatin and neuropeptide Y immunoreactivity in Parkinson's disease dementia with Alzheimer's changes

Somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) were measured in postmortem brain tissue from 12 control patients and 13 demented Parkinsonian patients who had Alzheimer-type cortical pathology. Twenty-two cortical regions were examined. Significant reductions in cortical SLI were found in 17 regions, while significant reductions in cortical NPYLI were found in nine regions. The reductions in SLI were typically 50-60%, while NPYLI reductions were 20-30%. These findings are similar to those in Alzheimer's disease (AD) and are consistent with a previous report of a dissociation between reductions in SLI and NPYLI in Parkinson's disease (PD) with dementia.

Loss of parvalbumin-immunoreactive neurones from cortex in Alzheimer-type dementia

The type and cell size of parvalbumin-immunoreactive (PV-Ir) neurones were examined in 14 postmortem brains from elderly control and Alzheimer-type dementia (ATD) patients with the aid of an image analyser. Morphological features of PV-Ir neurones suggested the existence of PV in the non-pyramidal interneurones in the cerebral cortex. A significant loss of PV-Ir cells was found in the frontal and temporal cortex in ATD. A significant reduction in the size of PV-Ir cells was also noted in the temporal cortex in ATD. These findings suggested that PV-Ir neurones in the cortex are affected in ATD.

The regional distribution of somatostatin and neuropeptide Y in control and Alzheimer's disease striatum

Somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) were measured in subdissections of both normal and Alzheimer's disease (AD) striatum at 5 coronal levels. Concentrations of both neuropeptides were relatively homogeneously distributed in the coronal and anterior-posterior planes except for a trend towards increased concentrations in the tail of the caudate and the posterior putamen. The nucleus accumbens showed 2-3-fold higher concentrations of both SLI and NPYLI than the rest of the striatum. There were no significant differences between control and AD brains. The high concentrations of SLI and NPYLI in the nucleus accumbens suggest that this region may receive somatostatin-neuropeptide Y afferents and that somatostatin and neuropeptide Y may play a role in the modulation of motor activity.

Somatostatin 28 and neuropeptide Y innervation in the septal area and related cortical and subcortical structures of the human brain. Distribution, relationships and evidence for differential coexistence

Somatostatin 28- and neuropeptide Y-containing innervations were mapped in the human medial forebrain (eight control brains) with immunohistochemistry, using the sensitive avidin-biotin-peroxidase method. Peptidergic perikarya and fibers had an extensive distribution: they were densest in the ventral striatum (nucleus accumbens, olfactory tubercle and bed nucleus of the stria terminalis) and infralimbic cortex, of intermediate density in the medial septal area and of lowest density in the dorsal and caudal lateral septal nucleus. Somatostatin-like immunoreactive perikarya and fibers were generally more numerous than the neuropeptide Y-like immunoreactive ones, but more faintly labeled. Their pattern of distribution was strikingly similar in some of the limbic structures studied but clearly distinct in others. Excellent overlap of neuropeptide Y and somatostatin-like immunoreactivity was detected in: (1) the medial septal area, where innervation occasionally formed perivascular clusters; (2) the nucleus accumbens and olfactory tubercle, characterized by dense patchy innervation; and (3) the laterodorsal septal nucleus, scarcely innervated. In the latter structures, most peptidergic neurons were double-labeled. On the other hand, both peptidergic innervations clearly differed in the lateroventral septal nucleus and the bed nucleus of the stria terminalis which contained distinct clusters of somatostatin-like immunoreactive neurons devoid of neuropeptide Y-like immunoreactivity. Also, the perineuronal and peridendritic axonal plexuses ('woolly fibers') present in these structures were only labeled with somatostatin. In the infralimbic cortex, the relation between the peptides varied according to the cortical laminae. Coexistence of somatostatin and neuropeptide Y frequently occurred in layer VI and in the subcortical white matter, whereas layer V and particularly layers II and III contained a contingent of neurons labeled only with somatostatin. Dense horizontal terminal networks in layers I and VI however were similar for both peptides. These findings support the existence of two different types of somatostatin-like immunoreactive perikarya as regards colocalization with neuropeptide Y. Their particular topographical segregation within the cortical and subcortical structures analysed suggest that they could have different connections and functional properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatostatin immunoreactive neurons in the human hippocampus and cortex shown by immunogold/silver intensification on vibratome sections: coexistence with neuropeptide Y neurons, and effects in Alzheimer-type dementia

The distribution of somatostatinlike immunoreactivity was studied in the hippocampal formation, retrohippocampal region, and temporal cortex in the human brain. Tissues from surgical biopsy and postmortem cases were used, and the immunogold/silver method on vibratome sections was introduced for routine applications in conjunction with primary antisera that recognise somatostatin-14 or somatostatin-28. Somatostatin-28 antisera readily stained numerous neurons, dendrites, and extensive axonal networks throughout the hippocampus and neighbouring cortex. Liquid phase absorption provided controls for specificity. The most prominent accumulations of somatostatin immunoreactive neurons and axons occurred in the hilus of the area dentata, in CA1, and in the entorhinal and perirhinal cortices. Axonal plexuses occurred throughout the hippocampal subfields but were particularly dense in those regions rich in somatostatin neurons. The distribution of somatostatin immunoreactive neurons and fibers parallels the distribution of neuropeptide Y (NPY) neurons and fibers in the hippocampus and cerebral cortex to a remarkable extent. Double labelling experiments with antisera against neuropeptide Y and somatostatin indicate a considerable frequency of coexistence of the two peptides in single neurons, particularly in large multipolar cortical neurons and also in the small bipolar white matter neurons. Regional variations exist in the amounts of coexistence found in the hippocampal subfields; somatostatin-NPY coexistence is particularly high in the hilus of the area dentata, the subicular complex, and the deep layers of the entorhinal and perirhinal cortices. In the hippocampi and temporal cortices in cases of Alzheimer-type dementia compared to those of age-matched control brains, there is a significant to severe loss of somatostatin immunoreactive neurons and axons. This loss is most severe in those regions with the highest indices of neurofibrillary tangles and neuritic plaques-the hilus of the area dentata, CA1, and the entorhinal and perirhinal cortices. Surviving somatostatin neurons are distorted with short dendrites and truncated axons. Neuritic plaques identified on double label experiments with thioflavin include somatostatin axons but not neurons.

Molecular structure of mammalian neuropeptide Y: analysis by molecular cloning and computer-aided comparison with crystal structure of avian homologue

Identification and characterization of the cDNA encoding rat neuropeptide Y revealed the nucleotide sequence coding for a 98-amino acid precursor. The deduced amino acid sequence for rat neuropeptide Y is identical to the human peptide and is highly homologous to avian pancreatic polypeptide. The tertiary structure of avian pancreatic polypeptide has been previously derived from crystallographic data by Blundell and coworkers. The homology between neuropeptide Y and avian pancreatic polypeptide preserves all of the residues essential for the maintenance of the tertiary structure. Thus, it has been possible to compute a three-dimensional model of the mammalian neuropeptide, neuropeptide Y, based on the known structure of the avian homologue. This model suggest that neuropeptide preserves a compact tertiary structure characterized by extensive hydrophobic interactions between an N-terminal polyproline-II-like helix and a C-terminal alpha-helix. The model has been used to identify amino acids residing in key positions within this structure and, thereby, to direct future analysis of neuropeptide Y structure-function relationships.

Neuropeptide Y, somatostatin, and reduced nicotinamide adenine dinucleotide phosphate diaphorase in the human striatum: a combined immunocytochemical and enzyme histochemical study

Neuropeptide Y and somatostatin immunoreactive neurons and processes were examined in human striatum using both immunofluorescence and avidin biotin immunoperoxidase methods. Reduced nicotinamide adenine dinucleotide phosphate diaphorase activity was histochemically determined by the reduction of nitro blue tetrazolium. Immunofluorescence using a monoclonal anti-somatostatin antibody and a polyclonal anti-neuropeptide Y antibody, followed by diaphorase histochemistry, showed that these three neurochemical markers are co-localized in a single population of medium-sized aspiny intrinsic neurons. Cells were evenly distributed in clusters throughout the striatum, but fiber density was higher in the nucleus accumbens and ventromedial regions of the caudate and putamen. Double-stained reduced nicotinamide adenine dinucleotide phosphate diaphorase-acetylcholinesterase sections demonstrated that these neurons are located in zones of high acetylcholinesterase activity, often at the interface of these zones with regions of low enzyme activity. These biochemically distinctive neurons are uniquely situated to modulate activity between striatal compartments. Our findings provide new information about the modular organization of the striatum and extend these observations in human brain.

Choline acetyltransferase immunoreactivity in neuritic plaques of Alzheimer brain

We have observed dystrophic choline acetyltransferase (ChAT)-positive processes surrounding the amyloid core of neuritic plaques in human neocortex, amygdala and hippocampus, using a polyclonal anti-human ChAT antiserum. These data, and those from studies of the aged monkey by other investigators, provide a morphologic counterpart for the biochemical abnormality of the cholinergic system in Alzheimer's disease and senile dementia of the Alzheimer type.

Neurotransmitter and receptor deficits in senile dementia of the Alzheimer type

Multiple neurotransmitter systems are affected in senile dementia of the Alzheimer's type (SDAT). Among them, acetylcholine has been most studied. It is now well accepted that the activity of the enzyme, choline acetyltransferase (ChAT) is much decreased in various brain regions including the frontal and temporal cortices, hippocampus and nucleus basalis of Meynert (nbm) in SDAT. Cortical M2-muscarinic and nicotinic cholinergic receptors are also decreased but only in a certain proportion (30-40%) of SDAT patients. For other systems, it appears that cortical serotonin (5-HT)-type 2 receptor binding sites are decreased in SDAT. This diminution in 5-HT2 receptors correlates well with the decreased levels of somatostatin-like immunoreactive materials found in the cortex of SDAT patients. Cortical somatostatin receptor binding sites are decreased in about one third of SDAT patients. Finally, neuropeptide Y and neuropeptide Y receptor binding sites are distributed in areas enriched in cholinergic cell bodies and nerve fiber terminals and it would be of interest to determine possible involvement of this peptide in SDAT. Thus, it appears that multi-drug clinical trials should be considered for the treatment of SDAT.