Dementia of the Alzheimer type

Neuropathological distinction between Parkinson's dementia and Parkinson's plus Alzheimer's disease

The distinctive clinical features of dementia in Parkinson's disease (PDD) and Parkinson's plus Alzheimer's disease (PD + AD) suggest different patterns of cerebral atrophy in these conditions. To determine the pathoanatomical substrates of dementia in PDD and PD + AD, morphometric analysis of 5 standardized coronal slices was used to identify volumetric changes in cerebral tissue. In PDD (n = 4) there were 9 to 23% reductions in cross-sectional area of cerebral cortex, a 38% loss of tissue in the globus pallidus + putamen, and an 18% reduction in area of the amygdala, whereas in PD + AD (n = 6) there was severe global atrophy of the cerebral cortex (27-29% reductions), moderate atrophy of white matter (10-19% reductions), and 40% reductions in areas of globus pallidus + putamen and the amygdala relative to neuropathologically intact controls (n = 14). Immunostaining with anti-glial fibrillary acidic protein disclosed significant gliosis of all four major subdivisions of neocortex in PD + AD and gray matter of the caudate, putamen, globus pallidus, and thalamus in both PDD and PD + AD relative to controls. The findings suggest that dementia in PDD is mainly subcortical in origin and due to neuronal degeneration in basal ganglia, the amygdala, and thalamus. In PD + AD the same pattern and degree of subcortical degeneration is evident, but there are clearly superimposed lesions involving cortical neurons and long projection fibers coursing through cerebral white matter that most likely account for the distinctive manifestations of dementia in this condition compared with PDD.

Growth hormone responses to growth hormone releasing factor in primary degenerative dementia

The growth hormone (GH), thyroid-stimulating hormone (TSH), and prolactin (PRL) responses to growth hormone releasing factor (GRF) were investigated in 18 patients suffering from primary degenerative dementia (PDD) and in 20 age- and sex-matched normal elderly controls. There was no significant difference in the growth hormone response to GRF stimulation between patients and controls, and in neither subject group was there a demonstrable TSH or prolactin response to GRF. These findings indicate that the pathophysiology underlying the blunted growth hormone response to pharmacological challenge in PDD must lie at a suprapituitary level.

Blockade of ACh receptors by PrBCM causes deficits in shuttle avoidance performance

Studies were made examining the effect of blockade of muscarinic acetylcholine (mACh) receptors in the cerebral cortex of rats on their shuttle avoidance after training. Rats were given a session of shuttle avoidance tests once a day for 12 days. Then the irreversible antagonist of mACh receptors, propylbenzilylcholine mustard (PrBCM), was injected bilaterally into the cerebral cortex of rats showing avoidance rates of more than 75% in the last session, and avoidance rates were examined 24 hr later. The avoidance rates of the rats treated with 100 micrograms PrBCM were lower than those in the last session before treatment. The amount of mACh receptors in the cerebral cortex was decreased by PrBCM treatment, as shown by [3H]quinuclidinyl benzilate (QNB) binding studies performed just after measurement of the avoidance response. The present study indicates that cholinergic neurotransmission in rat cerebral cortex is involved in performing a learned shuttle avoidance.

Nicotinic binding sites in cerebral cortex and hippocampus in Alzheimer's dementia

Postmortem cerebral neocortical and hippocampal samples were taken from patients who died with dementia of the Alzheimer type (DAT) and individuals without diagnoses of neurological or psychiatric disease (control). Nicotinic binding was assayed with 20 nM [3H]acetylcholine [( 3H]ACh) in the presence of atropine, or with 4 nM (-)-[3H]nicotine ((-)-[3H]Nic). Binding of both ligands was lower in the following regions from DAT vs. control brains (P less than or equal to 0.05): superior, middle and inferior temporal gyri, orbital frontal gyrus, middle frontal gyrus, pre- and postcentral gyri, inferior parietal lobule, and hippocampal endplate. Values of the correlation coefficient (r's) for binding of the nicotinic cholinergic ligands in these regions ranged from 0.70 to 0.93 (P's less than 0.05), suggesting that [3H]ACh and (-)-[3H]Nic labeled the same sites in human brain. There was no difference in nicotinic binding in the presubiculum, comparing DAT and control samples (P greater than 0.05). Here too, correlations between binding of the two ligands were statistically significant in control and DAT groups (r's = 0.92, P's less than 0.05). Nicotinic binding measured with [3H]ACh, but not (-)-[3H]Nic, was significantly lower in the H2 (field of Rose) and H1-subiculum areas of DAT samples compared to control. Correlations between binding of the two ligands in these regions ranged from 0.21 to 0.34 for the two groups (P's greater than 0.05). The findings support a loss of neocortical and hippocampal nicotinic cholinergic binding sites in DAT.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of evidence for a role of T-cell-associated retroviruses as an etiology of schizophrenia

The evidence that schizophrenia may involve infection by a virus (or viruses) has been indirect. The recent discovery, however, of the human retroviruses--human T-cell lymphoma-leukemia virus-I, and II (HTLV-I, -II) and human immunodeficiency virus (HIV)--now also known to affect the central nervous system (CNS), together with the development of new techniques in retrovirology, have made it possible to investigate more directly the role of this class of viruses as an etiology of schizophrenia. In our first effort to screen for the presence of a T-cell lymphotropic virus in schizophrenia, short-term tissue cultures of peripheral lymphocytes from 17 chronic schizophrenic patients and 10 normal controls were established. The cells were cultured in the presence of T-cell growth factor (TCGF, IL-2), and the culture supernatants were tested for the presence of the retroviral enzyme reverse transcriptase. No T-cell-associated reverse transcriptase activity was detected in cultures from patients or normal controls. Therefore, the data do not provide evidence for a role for T-cell lymphotropic retroviruses as an etiology of schizophrenia.

Effect of the 'antidementia drug' pantoyl-GABA on high affinity transport of choline and on the contents of choline and acetylcholine in rat brain

1. Effect of pantoyl-gamma-aminobutyric acid (pantoyl-GABA) on high affinity transport of choline into synaptosomes and on the choline (Ch) and acetylcholine (ACh) concentrations of rat brain were studied. 2. Pantoyl-GABA was injected intraperitoneally four times at a dose of 500 mg kg-1 at intervals of 30 min. One hour after the last injection, rats were killed by decapitation for measurement of high affinity transport of Ch into synaptosomes or by microwave irradiation for the measurement of Ch and ACh concentrations. 3. Transport of Ch was increased into synaptosomes prepared from the cerebral cortex and hippocampus, but not into those from the striatum. 4. In the cerebral cortex and hippocampus, Ch concentration was increased and ACh concentration decreased. 5. Since treatments that enhance the activity of cholinergic neurones in vivo are reported to increase high affinity transport of Ch measured in vitro, the present results suggest that pantoyl-GABA may increase cholinergic activity in vivo. This action of the drug may be related to changes in the Ch and ACh concentrations.

Reduced axonal transport of the G4 molecular form of acetylcholinesterase in the rat sciatic nerve during aging

Aging in the sciatic nerve of the rat is characterized by various alterations, mainly cytoskeletal impairment, the presence of residual bodies and glycogen deposits, and axonal dystrophies. These alterations could form a mechanical blockade in the axoplasm and disturb the axoplasmic transports. However, morphometric studies on the fiber distribution indicate that the increase of the axoplasmic compartment during aging could obviate this mechanical blockade. Analysis of the axoplasmic transport, using acetylcholinesterase (AChE) molecular forms as markers, demonstrates a reduction in the total AChE flow rate, which is entirely accounted for by a significant bidirectional 40-60% decrease in the rapid axonal transport of the G4 molecular form. However, the slow axoplasmic flow of G1 + G2 forms, as well as the rapid transport of the A12 form of AChE, remain unchanged. Our results support the hypothesis that the alterations observed in aged nerves might be related either to the impairment in the rapid transport of specific factor(s) or to modified exchanges between rapidly transported and stationary material along the nerves, rather than to a general defect in the axonal transport mechanisms themselves.

Effects of estradiol and dexamethasone on choline acetyltransferase activity in various rat brain regions

Estradiol, administered to ovariectomized rats, increased choline acetyltransferase (ChAT) activity in the caudate nucleus, cortex, hippocampus, and hypothalamus, suggesting possibly widespread central cholinergic involvement in estrus-related behavior. Dexamethasone also, except in hypothalamus, increased ChAT activity, notably (50%) in hippocampus. ChAT activity changes did not correlate with reported regional hormone receptor density. Estradiol's effect in the caudate suggests that hormone receptor and affected enzyme may not necessarily coexist intraneuronally.

Dopaminergic system and monoamine oxidase-B activity in Alzheimer's disease

The possible involvement of dopaminergic neurons in dementia of Alzheimer type (AD/SDAT) was studied in autopsied brains from 20 patients with AD/SDAT. Dopamine (DA) concentrations were decreased significantly in the temporal cortex, hippocampal cortex and hippocampus in AD/SDAT patients. Levels of homovanillic acid (HVA) were not altered compared to controls. The HVA/DA ratio was significantly higher in the hippocampus of AD/SDAT patients, suggesting overactivity of the remaining DA neurons. Histological findings of substantia nigra suggesting coexistent pathology of Parkinson's disease (PD) found in 25% of cases were associated with lowered levels of DA in striatum and with reduced HVA in CSF. The activity of monoamine oxidase-B was significantly increased in the cortical areas and in the hippocampus, obviously reflecting the underlying cell loss and substantial gliosis in these areas of the brain. In general, DA neurons seemed to be only mildly involved in AD/SDAT. Coexistent PD pathology can explain the loss of DA in the striatum and the presence of clinical PD symptoms in some patients with AD/SDAT. Otherwise the clinical relevance of these dopaminergic alterations is unclear.

Intraventricular administration of the cholinotoxin AF64A increases the accumulation of aluminum in the rat parietal cortex and hippocampus, but not in the frontal cortex

Aluminum (Al) concentrations of the rat frontal cortex, parietal cortex, and hippocampus were measured by atomic absorption spectroscopy 16 days after a unilateral intracerebroventricular injection of Na gluconate, Al gluconate, or the cholinotoxin AF64A. A fourth group of rats were injected with AF64A 6 days before injection of Al gluconate and subsequently sacrificed 10 days later. The combined treatment of AF64A and Al gluconate resulted in enhanced intraneuronal accumulation of Al in the parietal cortex and hippocampus but not in the frontal cortex. Consequently, Al may not be considered to be a primary factor in the pathogenesis of Alzheimer's disease.

VIP-sensitive adenylate cyclase, guanylate cyclase, muscarinic receptors, choline acetyltransferase and acetylcholinesterase, in brain tissue afflicted by Alzheimer's disease/senile dementia of the Alzheimer type

Biochemical parameters were determined in autopsy material from several brain regions of thirteen patients with Alzheimer's disease/senile dementia of Alzheimer type (AD/SDAT) (mean age 75 years) and from brains of ten age-matched controls (mean age 76 years). Choline acetyltransferase specific activity was significantly lower in the nucleus caudatus, putamen, left thalamus, hippocampus and the cortex from gyrus hippocampus and the temporal lobe in AD/SDAT, acetylcholinesterase specific activity was significantly lower in the hippocampus, parietal and left frontal lobe in AD/SDAT samples than in corresponding samples from aged-matched controls. A compensatory increase of muscarinic receptors was found in the nucleus caudatus and left frontal lobe samples in AD/SDAT. Guanylate cyclase activity was not significantly altered in AD/SDAT in the brain regions examined. The basal, non-stimulated activity of adenylate cyclase was significantly (p less than 0.05) elevated in hippocampus samples from AD/SDAT patients and the enzyme activity stimulated by the vasoactive intestinal polypeptide VIP (2 microM) or forskolin (10 microM) was also elevated in AD/SDAT although not significantly.

Effects of persistent lymphocytic choriomeningitis virus infection on cholinergic neurons in the mouse

We have examined the effects of persistent infection with the Armstrong E350 strain of lymphocytic choriomeningitis virus (LCMV) on choline acetyltransferase activity in several regions of Balb/c mouse brain. Despite the presence of high titres of virus in brain for as long as 6 months, and a widespread distribution of virus antigen, no decreases in choline acetyltransferase activity could be demonstrated. The enzyme activity was increased in some regions of brain, showing an effect of the persistent virus infection on a differentiated cell function. Although these data do not suggest a role for LCMV in human neurologic disease, similar studies may allow useful animal models to be conveniently and reproducibly generated.

Decreased level of nerve growth factor (NGF) and its messenger RNA in the aged rat brain

Trophic factors such as nerve growth factor (NGF) are thought to support survival, differentiation and maintenance of neurons. Recent results indicate that NGF produced in cortical and hippocampal areas is required for the function of cholinergic neurons in the basal forebrain. With the use of enzyme immunoassay and RNA blot hybridization we studied the NGF protein and NGF mRNA, respectively, in regions of the brain innervated by basal forebrain cholinergic neurons in adult and aged rats. Levels of NGF protein were decreased by 40% in hippocampus of aged (28 months) Fischer 344 rats compared with adults (6 months), whereas no alterations were observed in cerebral cortex. Moreover, a reduction by 50% in the NGF mRNA was found in samples of the aged forebrain (cerebral cortex, hippocampus, basal forebrain and hypothalamus) compared to the adult. NGF deficiencies may thus account for the loss of cholinergic neurons in the basal forebrain generally found to accompany normal aging and resulting in altered cognitive functions.

Plasticity of the synaptic contact zone following loss of synapses in the cerebral cortex of aging humans

Quantitative ultrastructural analyses of ethanolic phosphotungstic acid-stained human layer 1 precentral motor cortex (Brodmann's area 4) and layer 1 postcentral somatosensory cortex (Brodmann's area 3) were undertaken to determine the nature of synaptic changes occurring over a series of ages (45-84 years) of a normal aging human population. In the precentral cortex, a significant decrease in the number of synapses was accompanied by an increase in mean length of the postsynaptic contact zone and a decrease in the mean width of the presynaptic paramembranous density. The frequency of mature type A and immature type E synaptic profiles decreased with age. There were no changes in the width of the postsynaptic paramembranous density, cleft width or the number of presynaptic dense projections per synapse. In the postcentral cortex there were no significant changes in synaptic number or in any of the synaptic parameters measured. The present study demonstrates that age-related synapse loss in the human cerebral cortex may be confined to specific cortical regions. The data suggest that in the precentral cortex the plasticity of the synaptic contact zone may be a compensatory response by the remaining synapses to age-related synapse loss.

Molecular biology and neurobiology of choline acetyltransferase

In the 45 years since the first description of choline acetyltransferase (ChAT; EC 2.3.1.6.), significant progress has been made in characterizing the molecular properties of this important neurotransmitter synthetic enzyme. We are now on the verge of understanding its genetic regulation and biological function(s). The Drosophila cDNA has been cloned, sequenced, and expressed in both a eucaryotic and a procaryotic system. The levels of ChAT specific mRNA have been determined during Drosophila development. Monoclonal and polyclonal antibodies have been produced to the enzyme from a variety of sources and used for biochemical and immunocytochemical studies. Two well characterized genetic systems have identified the ChAT gene and described a series of useful alleles. As a nervous system specific protein expressed only in the subset of neurons using acetylcholine as a neurotransmitter, ChAT is a good model for uncovering the processes and factors responsible for regulating genes involved in neurotransmitter phenotype selection and maintenance. Recent studies have described the purification of a cholinergic factor from muscle conditioned medium and indicated the potential importance of nerve growth factor (NGF) for regulating ChAT expression in the central nervous system. These factors, or ones remaining to be discovered, may be involved in the etiology or disease process of neurodegenerative nervous system disorders such as Alzheimer's disease.

Genetic linkage in the mouse of genes involved in Down syndrome and Alzheimer's disease in man

Recently, the gene encoding the cerebrovascular and neuritic plaque amyloid, a pathologic stigma of Alzheimer's disease (AD), has been molecularly cloned and mapped to human chromosome 21, band q21. Changes in the brains of individuals with trisomy 21 (Down syndrome, DS) over 35 years of age closely resemble AD neuropathology. Genetic homology which exists between human chromosome 21 (HSA 21) and mouse chromosome 16 (MMU 16) has led to the use of mice with trisomy 16 as a model system for studies relevant to DS. Mice with Ts16 exhibit numerous developmental abnormalities that can be correlated with features observed in DS, including neurochemical and neuroanatomic alterations. In this study, we show that the genetic homology between HSA 21 and MMU 16 extends to the gene encoding the amyloid peptide. The homologous mouse gene, designated Cvap, for cerebrovascular amyloid peptide, is localized on MMU 16 band C3----ter, and is in close proximity to both superoxide dismutase-1 (Sod-1), and the protooncogene, Ets-2, two of the genes known to localize to the DS region of HSA 21. Linkage of these genes has been maintained since the divergence of the common ancestor of mouse and man, despite a chromosomal rearrangement which has changed the gene order between the two species. These findings expand the region of HSA 21 with known homology to MMU 16, and provide a genetic basis to suggest that studies of the trisomy 16 mouse, in addition to being relevant to DS, may also clarify the role of abnormal gene expression in AD.

Cortical projection patterns of magnocellular basal nucleus subdivisions as revealed by anterogradely transported Phaseolus vulgaris leucoagglutinin

The present paper deals with a detailed analysis of cortical projections from the magnocellular basal nucleus (MBN) and horizontal limb of the diagonal band of Broca (HDB) in the rat. The MBN and HDB were injected iontophoretically with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). After immunocytochemical visualization of labeled efferents, the distribution of projections over the cortical mantle, olfactory regions and amygdala were studied by light microscopy. Based on differences in cortical projection patterns, the MBN was subdivided in anterior, intermediate and posterior portions (MBNa, MBNi and MBNp). All subdivisions maintain neocortical projections and are subject to an anterior to posterior topographic arrangement. In the overall pattern, however, the frontal cortex is the chief target. Furthermore, all MBN parts project to various regions of meso- and allocortex, which are progressively more dense when the tracer injection is more anteriorly placed. The most conspicuous finding, however, was a ventrolateral to dorsomedial cortical projection pattern as the PHA-L injection site moved from posterior to anterior. Thus, the posterior MBN projects predominantly to lateral neo- and mesocortex while the anterior MBN sends more fibers to the medial cortical regions. Furthermore, the MBNa is a source of considerable afferent input to the olfactory nuclei and as such should be regarded as a transition to the HDB. The HDB, apart from projecting densely to olfactory bulb and related nuclei, maintains a substantial output to the medial prefrontal cortical regions and entorhinal cortex, as well. Comparison of young vs aged cases indicate that aging does not appear to have a profound influence on cortical innervation patterns, at least as studied with the PHA-L method.

Comparison of synaptic changes in the precentral and postcentral cerebral cortex of aging humans: a quantitative ultrastructural study

Ultrastructural quantitative analysis was undertaken to determine whether any age-related synaptic changes occur in cortical layer 1 of the human precentral motor gyrus (Brodmann's area 4) and postcentral somatosensory gyrus (Brodmann's area 3). Immersion fixed, osmicated, uranyl acetate/lead citrate stained (OsUL) preparations of autopsied brains were taken from patients aged 45 to 84 years, with no prior history of neurological or intellectual abnormalities. In the precentral gyrus there was a significant decrease in the number of synapses, which was primarily due to a decrease in asymmetrical axospinous synapses. Symmetrical synapses remained constant in number, while axodendritic synapses showed a small increase with age. Accompanying the decline in synapse number was an increase in mean length of the postsynaptic contact zone. In the postcentral gyrus there were no significant changes in synaptic number or in any of the synaptic parameters measured. The results suggest that the motor cortex of the human brain is capable of synaptic plasticity in response to aging-induced synaptic loss. This plasticity is not apparent in the somatosensory cortex, where there is no age-related synapse loss.

Colchicine lesions in the rat hippocampus mimic the alterations of several markers in Alzheimer's disease

An infusion of colchicine into the hippocampi of rats resulted in destruction of hippocampal cells. Twelve days after infusion, preoperative trained colchicine-treated rats showed a significant decrease in choice accuracy in a T-maze learning task. There was also local reduction in choline acetyltransferase (ChAT) activity and significant losses of 55-kDa protein in the soluble fraction and of 50-kDa protein in myelin and synaptosomal fractions in the hippocampi of colchicine-lesioned rats. There was a marked increase in [3H]glutamate binding in the hippocampus and cortex. In contrast, [3H]quinuclidinyl benzilate binding in the hippocampus was slightly reduced, whereas [3H]dihydroalprenolol binding was not affected by the colchicine treatment. Scatchard analysis revealed that the increase in glutamate binding is due to an increase in the number of glutamate receptors without significant change in their affinity. Some of the changes caused by hippocampal infusion of colchicine resemble those seen in Alzheimer's disease suggesting the use of such rats as one model for the disease.

Detailed projection patterns of septal and diagonal band efferents to the hippocampus in the rat with emphasis on innervation of CA1 and dentate gyrus

The detailed patterns of afferentation to the ammon's horn and dentate gyrus of the hippocampus in the rat were investigated employing the anterograde tracer Phaseolus vulgaris leuco-agglutinin (PHA-L) after punctate iontophoretic injections in the medial septum (MS) and vertical limb of the diagonal band of Broca (VDB). The topographically ordered innervation pattern was different in the regio superior (or CA1) vs. the regio inferior (or CA3) and in the dorsal vs. ventral aspects of ammon's horn and dentate gyrus. The CA1 pyramidal and dentate granule cell layers in the dorsal hippocampus received afferent input almost exclusively from the VDB, whereas those cell layers in ventral hippocampus were supplied from both VDB and MS. The PHA-L labeled projecting fibers could be differentiated into two distinct fiber systems. One class of thick and coarse axons (tentatively called type I fibers) carried fewer but larger terminal boutons and were found to infiltrate the entire stratum oriens, dentate hilus, all layers of the regio inferior and the CA1 str. moleculare. A second, delicate thin (type II) fiber system provided with numerous and passant varicosities showed a much more restricted laminar innervation pattern and appeared to originate from areas in MS-VDB which are rich in AChE-positive neurons. The densest type II fiber networks could be observed in the CA1 subpyramidal and dentate supragranular zones, in the CA1 stratum lacunosum-moleculare and in the dentate middle third molecular layer. This laminar type II innervation pattern showed a remarkable coincidence with the reported distribution of cholinergic marker enzymes. The topographic and spatial organization of the projections described above will be discussed in relation to their possible functional significance.

Blood-brain barrier in Alzheimer dementia and in non-demented elderly. An immunocytochemical study

Peroxidase-antiperoxidase staining of formalin-fixed brain was employed to compare the blood-brain barrier (BBB) function in five patients with Alzheimer's disease/senile dementia of the Alzheimer type (AD/SDAT) and three patients with AD/SDAT combined with multi-infarct dementia (MID/SDAT) with that of six non-demented aged controls. The diffusion of serum proteins through the BBB was visualized with antisera to albumin, prealbumin, immunoglobulin, C1q, C3c and to fibrinogen. A similar patterns of diffusion was seen in AD/SDAT and non-demented aged individuals. Neuron and glial cells were stained with different antisera in the vicinity of the diffusion. Senile (neuritic) plaques were occasionally visualized with antisera to IgG, C1q and C3c but not with antisera to albumin, prealbumin and fibrinogen in both demented and non-demented aged individuals. Neurofibrillary tangles were not labelled with any of the antisera studied. These results indicate that the BBB is compromised equally in AD/SDAT and in the non-demented elderly.

Blockade of cholinergic receptors by an irreversible antagonist, propylbenzilylcholine mustard (PrBCM), in the rat cerebral cortex causes deficits in passive avoidance learning

Studies were made on the effects of blockade of muscarinic acetylcholine (mACh) receptors in the rat cerebral cortex on learning and memory assessed by performance of a step-through passive avoidance task. Bilateral injection of propylbenzilylcholine mustard (PrBCM) into both the frontal and parietal cortex at doses of 2.25 X 4 to 22.5 X 4 micrograms decreased mACh receptors dose-dependently, as assessed by [3H]quinuclidinyl benzilate binding studies. When the training trial of a step-through passive avoidance task was performed 24 h after injection of 7.5 X 4 to 22.5 X 4 micrograms PrBCM into the frontal and parietal cortex, and then a retention test was made 24 h after the training trial, the treated rats showed shorter latencies than controls. In contrast, injection of PrBCM into the occipital cortex had no significant effect on performance in the test. These results confirm the notion that cholinergic neurotransmission in the cerebral cortex, especially the frontoparietal cortex, is important in learning and memory. The effects of injection of PrBCM (22.5 X 4 micrograms) into the frontoparietal cortex on 3 postulated phases of the learning and memory process (i.e. registration, retention and recall) were also examined. When PrBCM was injected 24 h before the training trial, no retention of the task was observed 14 days after the training trial. However, when PrBCM was injected 24 h after the training trial, retention of the task 14 days after the training trial was not affected. When PrBCM was injected 3-24 h after the initial training trial, the latencies in the retention test examined 24 h later were shorter than those of control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The localization and distribution of high affinity beta-nerve growth factor binding sites in the central nervous system of the adult rat. A light microscopic autoradiographic study using [125I]beta-nerve growth factor

Although beta-nerve growth factor is primarily known for its trophic role in the peripheral nervous system, recent reports have also revealed an inductive effect of beta-nerve growth factor on the cholinergic metabolism of the forebrain. To learn more about the significance and location of beta-nerve growth factor action in the central nervous system, the distribution of [125I]beta-nerve growth factor binding sites was studied by using the method of in situ receptor autoradiography and compared with the distribution of acetylcholinesterase, a sensitive enzyme marker of cholinergic neurons. The autoradiographic studies demonstrated strong, specific and saturable [125I]beta-nerve growth factor binding to several neuronal groupings in the forebrain and brainstem. beta-Nerve growth factor binding sites and strong acetylcholinesterase reactivity were jointly distributed in the forebrain on the medial septal nucleus, the diagonal band of Broca, the magnocellular basal nucleus and in the striatum. In the brainstem, beta-nerve growth factor binding sites were located on a number of neuronal groups in the reticular formation, the dorsolateral lemniscus and the cochlear nuclei. In contrast to the forebrain, less correlation was found with the distribution of acetylcholinesterase; no beta-nerve growth factor receptor expression was recorded on the cholinergic motor nuclei of the brainstem, while specific [125I]beta-nerve growth factor labeling could be located on the non-cholinergic cochlear nuclei. The present autoradiographic studies reveal a variety of tentatively beta-nerve growth factor receptor-positive neurons in the central nervous system. While strong correlation between the cholinergic metabolism and the presence of specific beta-nerve growth factor binding is demonstrated in the forebrain, this observation could not be extended to the brainstem, indicating the chemical diversity of central beta-nerve growth factor receptor-positive neurons.

Quantitative light microscopic autoradiographic localization of cholinergic muscarinic receptors in the human brain: forebrain

The distribution of muscarinic cholinergic receptors in the human forebrain and cerebellum was studied in detail by quantitative autoradiography using N-[3H]methylscopolamine as a ligand. Only postmortem tissue from patients free of neurological diseases was used in this study. The highest densities of muscarinic cholinergic receptors were found in the striatum, olfactory tubercle and tuberal nuclei of the hypothalamus. Intermediate to high densities were observed in the amygdala, hippocampal formation and cerebral cortex. In the thalamus muscarinic cholinergic receptors were heterogeneously distributed, with densities ranging from very low to intermediate or high. N-[3H]Methylscopolamine binding was low in the hypothalamus, globus pallidus and basal forebrain nuclei, and very low in the cerebellum and white matter tracts. The localization of the putative muscarinic cholinergic receptors subtypes M1 and M2 was analysed in parallel using carbachol and pirenzepine at a single concentration to partially inhibit N-[3H]methylscopolamine binding. Mixed populations of both subtypes were found in all regions. M1 sites were largely predominant in the basal ganglia, amygdala and hippocampus, and constituted the majority of muscarinic cholinergic receptors in the cerebral cortex. M2 sites were preferentially localized in the diencephalon, basal forebrain and cerebellum. In some areas such as the striatum and substantia innominata there was a tendency to lower densities of muscarinic cholinergic receptors with increasing age. In general, we observed a slight decrease in M2 sites in elderly cases. Muscarinic cholinergic receptor concentrations seemed to be reduced following longer postmortem periods. The distribution of acetylcholinesterase was also studied using histochemical methods, and compared with the localization of muscarinic cholinergic receptors and other cholinergic markers. The correlation between the presence of muscarinic cholinergic receptors and the involvement of cholinergic mechanisms in the function of specific brain areas is discussed. Their implication in neurological diseases is also reviewed.

Continuous infusion of nerve growth factor prevents basal forebrain neuronal death after fimbria fornix transection

Neurons in the rat medial septum (MS) and vertical limb of the diagonal band of Broca (VDB) undergo a rapid and severe cell death after transection of their dorsal projection to the hippocampus by aspiration of the ipsilateral fimbria fornix and supracallosal striae. By 2 weeks posttransection, the extent of neuronal loss was 50% of the total neurons and 70% of the cholinergic neurons in the MS and 30% of the total neurons and 40% of the cholinergic neurons in the VDB. We hypothesized that (i) the death was due to the loss of a hippocampus-derived neuronotrophic factor, and (ii) exogenous nerve growth factor (NGF) might provide trophic support to the MS/VDB cholinergic neurons, in light of recent reports that the septal diagonal band cholinergic neurons are responsive to NGF and that NGF is present and produced in the hippocampus. In the present study, we attempted to prevent the transection-induced neuronal death by continuous infusion of exogenous 7S NGF (1 microgram/wk) through an intraventricular cannula device. We report here that NGF treatment significantly reduces both the total neuronal and cholinergic neuronal death found 2 weeks after fimbria fornix transection; there was a sparing of 50% of the neurons in the MS and essentially 100% of those in the VDB that otherwise would have died. We conclude that NGF also has a protective effect on noncholinergic neurons since calculations indicate that 80% of the NGF-affected neurons are noncholinergic.

Increased corticotropin-releasing factor receptors in rat cerebral cortex following chronic atropine treatment

Rats were treated chronically with atropine (14 days, 20 mg/kg/day, s.c.) and corticotropin-releasing factor (CRF) receptors and CRF-mediated adenylate cyclase activity were measured in discrete brain regions. Chronic atropine treatment produced significant increases in muscarinic cholinergic receptors in the frontoparietal cortex (30% increase) and hippocampus (20% increase). No significant changes in the concentration of [125I]Tyr0-rat CRF binding sites were observed in olfactory bulb, cerebellum, striatum and hippocampus. In contrast, there was a significant and selective increase (35%) in CRF receptors in the frontoparietal cortex of atropine-treated rats. However, no significant corresponding changes in the Vmax or EC50 of CRF-stimulated adenylate cyclase activity accompanied the upregulation of CRF receptors in the cerebral cortex. These results demonstrate that CRF receptors in rat brain are subject to receptor regulation, the upregulation of CRF receptors occurs as a consequence of chronic muscarinic cholinergic receptor blockade, and this interaction between acetylcholine and CRF may be limited to the cerebral cortex.

Alzheimer's disease: maintenance of neuronal and synaptic densities in frontal cortical layers II and III

Neuronal loss and alterations of the cortical neuropil were previously described on necropsic material from patients with senile dementia of the Alzheimer type, and the results compared to age-matched case controls. In frontal cortex biopsic material from our patients with Alzheimer's disease, the numerical densities of neurons and synapses were not significantly different from controls, indicating that changes in the highest cognitive functions might not depend on a generalized loss of neurons and synapses and that quantitative morphological differences may exist between Alzheimer's disease and senile dementia of the Alzheimer type.

Muscarinic binding and choline acetyltransferase in postmortem brains of demented patients

Postmortem human brain samples were taken from non-neurological controls as well as demented subjects who died with Alzheimer's disease (AD), multi-infarct dementia (MID), or a combination of AD and MID dementia (MIXED). Choline acetyltransferase (ChAT) activity was measured radiometrically using [1-14C]acetyl-coenzyme A as the substrate, muscarinic binding was assayed with [3H]quinuclidinyl benzilate, and the proportion of binding associated with high affinity agonist sites was measured by carbamylcholine displacement of the radioligand. Relative to control, ChAT activity was significantly reduced (p less than or equal to 0.01) in samples taken from the temporal, frontal, and hippocampal areas of demented patients. A small elevation in Bmax was noted in the hippocampal endplate (p less than or equal to 0.01) (AD vs. control) and the H1-subiculum region (p less than or equal to 0.05) (AD vs. all other groups). In addition, the percentage of binding associated with high affinity agonist sites was greater in the frontal cortex of AD and MID samples (p less than or equal to 0.05). The results suggest a regionally specific upregulation of cerebral muscarinic receptors in dementia, especially in AD.

Dementia in movement disorders

Of all the movement disorders, Huntington's disease has been most consistently associated with dementia, while it is only over the last decade that intellectual cognitive decline have been recognized as common features of Parkinson's disease. It is now known that the pathology in these two conditions reflects differential involvement of the striatum. The Huntington lesion is primarily in the caudate, while the Parkinson lesion preferentially affects the putamen. Both conditions have more diffuse pathology, and dementia may also occur in a wide range of other extrapyramidal diseases, such as progressive supranuclear palsy, the parkinsonism-dementia complex of Guam, and certain spinocerebellar degenerations. Clinicopathological correlations will be reviewed in these disorders of primarily subcortical pathology, and comparisons will be made with Alzheimer's disease, a disorder of predominantly cortical pathology.

Cholinergic function and memory: extensive inhibition of choline acetyltransferase fails to impair radial maze performance in rats

The present study investigated the effects of a potent inhibitor of choline acetyltransferase (ChAT), BW813U, on the choice accuracy of rats in the radial arm maze. BW813U (100 mg/kg, IP) produced a rapid (within 1 hour) and substantial decrease in ChAT activity throughout the brain, ranging from 66% (hippocampus) to 80% (caudate nucleus) that lasted up to 5 days. A single injection (50 mg/kg, IP) into rats with lesions (using ibotenic acid) in the nucleus basalis magnocellularis and medial septal area, decreased ChAT activity by 75% and 60% in the cortex and hippocampus, respectively. Lesioned and unlesioned rats were trained on the radial arm maze until they reached a criterion level of performance. Each rat then received an injection of BW813U (50 or 100 mg/kg, IP). Choice accuracy was not impaired at any time following the injection. The lack of effect on performance may be due to 2 possible factors: The radial maze retention paradigm chosen may not be sufficiently difficult, or the decrease in acetylcholine production was not sufficient to affect behavior. Compensation by non-cholinergic neural systems might account for the insensitivity of the rats to significant cholinergic depletion.

Antemortem markers of Alzheimer's disease

This review examines various approaches to the development of antemortem markers of Alzheimer's disease. Among the procedures discussed are: neurochemical and histopathologic studies of the cholinergic system, concentrating on CSF and blood plasma; genetic studies; imaging and electrophysiological studies; and neuroendocrine studies.

Patients with Alzheimer's disease show an increased content of 15 Kdalton somatostatin precursor and a lowered level of tetradecapeptide in their cerebrospinal fluid

The relative proportions of both somatostatin-14 and its precursors somatostatin-28 and the 15 Kdalton prosomatostatin were evaluated by radioimmunoassay in the cerebrospinal fluid of patients with Alzheimer's disease. It was observed that the patients have a lowered content in the tetradecapeptide somatostatin while they exhibit a significant increase in unprocessed 15 Kda precursor. These results indicate that these patients possess impaired processing mechanisms which may be responsible for the lowered content in mature somatostatin-14. These observations may provide a valuable test for the ante-mortem diagnosis of the disease. They are discussed in connection with others suggesting that Alzheimer's patients may be selectively altered in their somatostatinergic neurones of their cerebral cortex (Morrison et al. (1985) Nature 314, 90-92. Roberts et al. (1985) Nature 314, 92-94).

Opioid peptides in the cerebrospinal fluid of Alzheimer patients

Endogenous opioid receptoractive peptides in the cerebrospinal fluid (CSF) of human controls and in those patients diagnosed as having senile dementia of the Alzheimer's type (SDAT) are measured with a radioreceptorassay following HPLC separation. [3H]Etorphine is the ligand used to detect in the HPLC fractions the presence of those endogenous peptides that preferentially interact with several opioid receptors. The RRA uses a receptor-rich P2 fraction extracted from a canine limbic system. The total opioid peptide content found in the HPLC fractions 6-20 (to avoid salts in fractions 1-5) of SDAT CSF (383 +/- 187 pmol ME-equivalents per ml CSF) is significantly higher than the corresponding total from patients with no known neurological disorders (89.1 +/- 46.3 pmol ME-equivalents per ml).

The neurobiologic consequences of Down syndrome

Trisomy of the whole or distal part of human chromosome 21 (HSA 21) (Ts21) results in Down Syndrome (DS), which is characterized in part by mental retardation and associated neurological abnormalities. Structural abnormalities observed frequently include reduced brain weight, decreased number and depth of sulci in the cerebral cortices, neuronal heterotopias, and reduced numbers of specific populations of neurons, such as granule cells, in the cerebral cortices. Abnormalities in the structure of cells, primarily of the dendrites, are observed in portions of the neuraxis, such as the hippocampus, cerebellum, and cerebral cortices. Functional abnormalities in membrane properties in peripheral structures and in neurotransmitter enzyme systems in both peripheral and central structures are observed also. Brains of DS individuals over the age of 40 exhibit the characteristic neuropathologic and neurochemical stigmata of Alzheimer's disease (AD). The cholinergic and noradrenergic systems appear to be particularly vulnerable. To elucidate the mechanisms responsible for these abnormalities, identification of the genes located in the distal part of HSA 21 and the systematic study of animal model systems with close genetic homology are essential.

Astrocytes produce interferon that enhances the expression of H-2 antigens on a subpopulation of brain cells

Using primary culture methods, we show that purified astrocytes from embryonic mouse or rat central nervous system (CNS) can be induced to produce interferon (IFN) activity when pretreated with a standard IFN-superinducing regimen of polyribonucleotide, cycloheximide, and actinomycin D, whereas IFN activity was not inducible in neuronal cultures derived from mouse CNS. Astrocyte IFN displays inductive, kinetic, physicochemical, and antigenic properties similar to those of IFN-alpha/beta, but is dissimilar to lymphocyte IFN (IFN-gamma). Treatment of pure astrocytic cultures or astrocytes cultured with neurons with astrocyte IFN or IFN-alpha/beta induced a dramatic increase in the expression of H-2 antigens on a subpopulation of astrocytes. Neither neurons nor oligodendroglia expressed detectable levels of H-2 antigens when exposed to astrocyte IFN, IFN-alpha/beta, or to IFN-beta. Injection of astrocyte IFN or IFN-alpha/beta directly into brains of newborn mice indicated that H-2 antigens were also induced in vivo. None of the IFNs (astrocyte, alpha/beta, or beta) tested induced Ia antigens on CNS cells in vitro or in vivo. Since H-2 antigens have a critical role in immune responses, astrocyte IFN may initiate and participate in immune reactions that contribute to immunoprotective and immunopathological responses in the CNS.

Prenatal development of nucleus basalis complex and related fiber systems in man: a histochemical study

To provide parameters for study of the "cholinergic" innervation of a human fetal cerebrum, we have analyzed the prenatal development of histochemical reactivity in the nucleus basalis complex (a magnocellular complex known to contain a high concentration of cholinergic perikarya). Brains from fetuses and premature infants ranging between 8 and 35 weeks of gestation were frozen cut and processed by the thiocholine method for the demonstration of acetylcholinesterase activity. Since no consistent results were obtained with inhibitors on the material younger than 15 weeks, the histochemical reactivity for early stages was expressed as the total cholinesterase reactivity. The first sign of histochemical differentiation of the basal telencephalon is the appearance of a dark cholinesterase reactive "spot" situated between the developing lenticular nucleus and basal telencephalon surface as early as 9 weeks of gestation. The first cholinesterase reactive bundle connects this reactive area (nucleus basalis complex anlage) with the strongly reactive fiber system situated along the dorsal side of the optic tract. During the next "stage" (10.5 weeks), there is a significant increase in the size of the nucleus basalis complex and strongly cholinesterase reactive neuropil occupies the sublenticular, diagonal and septal areas. At this stage we have seen two new cholinesterase-reactive bundles: one well developed cholinesterase reactive fiber stratum approaching (but not penetrating) the neocortical anlage through the external capsule and another minute bundle running towards the medial limbic cortex through the precommissural septum. The supraoptic fiber system can be traced now to the pregeniculate area and the tegmentum. At 15 weeks, the first acetylcholinesterase reactive perikarya appear and the nucleus basalis complex anlage becomes segregated into several strongly reactive territories, corresponding in position to the medial septal, diagonal and basal nuclei as defined on adjacent Nissl stained sections. At this stage, fibers from the nucleus basalis complex enter the "white" matter of frontal, temporal, parietal and occipital parts of the cerebral hemisphere via the external capsule. Between 15 and 18 weeks, acetylcholinesterase fibers spread throughout the "white" matter of the cerebral hemisphere. In the next "stage" (18-22 weeks), strongly reactive fibers can be followed from the nucleus basalis below the putamen and through the external capsule to the transient, synapse-rich subplate zone of frontal, temporal, parietal and occipital cortices.(ABSTRACT TRUNCATED AT 400 WORDS)

Divergent regulation of muscarinic binding sites and acetylcholinesterase in discrete regions of the developing human fetal brain

The expression of muscarinic acetylcholine binding sites and of cholinesterases was studied in extracts prepared from discrete regions of the human fetal brain, between the gestational ages of 14 and 24 weeks. The specific binding of [3H]N-methyl-4-piperidyl benzilate [( 4H]-4NMPB) to muscarinic binding sites ranged between 0.05 and 1.30 pmol/mg protein in the different brain regions, with Kd values of 1.2 +/- 0.2 nM. Binding of the cholinergic agonist oxotremorine fitted, in most of the brain regions examined, with a two-site model for the muscarinic binding sites. The density of muscarinic binding sites increased with development in most regions, with different rates and onset times. It was higher by about sixfold in some areas destined to become cholinergic, such as the cortex and midbrain, than in noncholinergic areas such as the cerebellum. In other areas destined to become cholinergic, such as the hippocampus and the caudate putamen, the receptor density remained low. Average density values increased from 0.1 +/- 0.1 at 14 weeks up to 0.7 +/- 0.4 pmol/mg protein at 24 weeks. The variability in the specific activities of cholinesterase was relatively low, and extracts from different brain regions hydrolyzed from 5 to 30 nmol of [3H]acetylcholine/min/mg protein. These were mostly "true" acetylcholinesterase (EC 3.1.1.7) activities, inhibited by 10(-5) M BW284C51, with minor pseudocholinesterase (EC 3.1.1.8) activities, inhibited by 10(-5) M iso-OMPA. The enzyme from different brain regions and developmental stages displayed similar Km values toward [3H]acetylcholine (ca. 4 X 10(-4) M-1). The ontogenetic changes in cholinesterase specific activities had no unifying pattern and/or relationship to the cholinergic nature of the various brain areas. In most of the brain regions, the arbitrary ratio between the specific activity of cholinesterase and the density of muscarinic binding sites decreased with development, with average values and variability ranges of 83 +/- 50 and 19 +/- 19 at 14 and 24 weeks, respectively. Our findings suggest divergent regulation for cholinergic binding sites and cholinesterase in the fetal human brain and imply that the expression of muscarinic receptors is related to the development of cholinergic transmission, while acetylcholinesterase is also involved in other functions in the fetal human brain.

Distribution of the molecular forms of acetylcholinesterase in human brain: alterations in dementia of the Alzheimer type

Acetylcholinesterase (AChE), the enzyme that degrades acetylcholine, is a heterogeneous enzyme that can be separated into multiple molecular forms. A tetrameric membrane-bound form (G4) and a monomeric soluble form (G1) are the two predominant enzyme species in mammalian brain. The distribution of AChE molecular forms was defined by sucrose density gradients of 11 anatomical regions of postmortem brains from 10 patients with dementia of the Alzheimer type (DAT) and 14 nondemented controls of similar ages. The results demonstrate an overall loss of protein and enzyme activity in all areas of the DAT brains studied and a selective loss of the G4 form of AChE in Brodmann areas 9, 10, 11, 21, 22, and 40, and the amygdala. There was no change in the G4/G1 ratio in areas 17 and 20, in the hippocampus, or in the cerebellum. There was a high regional correlation of the G4/G1 ratios with published values for choline acetyltransferase activity but lower correlation with total AChE activity. We propose that there is a predominant loss of the G4 form of AChE in DAT and that this loss is correlated with the degeneration of presynaptic elements.