Neurochemical activities in human temporal lobe related to aging and Alzheimer-type changes

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.

Degenerative Changes in Forebrain Cholinergic Nuclei Correlate with Cognitive Impairments in Aged Rats

Degenerative changes in the forebrain cholinergic nuclei have been studied morphometrically in behaviourally characterized aged female Sprague-Dawley rats. In all regions analysed (medial septum, diagonal band of Broca, nucleus basalis, and striatum) the acetylcholinesterase-positive neurons were reduced in both size and number in the aged (24-months-old) rats as compared to the young (3-months-old) controls. The overall reduction in cell size amounted to between 20 and 30% and the overall reduction in cell number to between 27 and 45%. Impairment in learning and/or memory performance in the aged rats, as assessed in the Morris' water-maze task, was significantly correlated with both cholinergic cell size and cell number in the medial septum, and with cholinergic cell number in the diagonal band of Broca and in the striatum. In the nucleus basalis there was a trend in the same direction but it did not reach significance. In contrast to these degenerative changes in the cell body regions, no significant differences in cortical or hippocampal choline acetyltransferase activity were detected biochemically between the young and the aged rats, and the enzyme activity levels did not correlate with the degree of behavioural impairment in the aged rats. The present results provide evidence that all major forebrain cholinergic cell groups undergo degenerative changes with age in the rat, and that the most severe changes are found in those rats which display the most profound spatial learning impairments. Despite the severe changes at the cell body level, however, the choline acetyltransferase activity in the cortical projection areas are affected only to a minor degree, perhaps as a result of functional compensatory changes at the terminal level.

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.

Experimental approaches to age-related cognitive impairments

Rats exhibit morphological, biochemical, and metabolic changes in their brains, as well as cognitive deficits, with aging. Aged rats were found to be significantly impaired compared to young rats in a water maze task and test of motor coordination, and show reduced locomotor activity and exploration. Although aged rats did exhibit deficits as a group, not all aged rats were impaired. Additionally, the subgroup that was impaired on one task was not necessarily the subgroup that was impaired on another task. The cholinergic projection neurons in the basal forebrain region were significantly atrophied in the aged rodent. The degree of atrophy was highly correlated with the cognitive impairment exhibited on the Morris water maze task. Swollen choline acetyltransferase (ChAT)-positive "plaque-like" structures were observed in the neocortex of the aged but not the young rats. Declines in cholinergic activity in the brain has also been observed during aging. Biochemical measurements of ChAT in the basal forebrain region of aged rats revealed small but consistent decreases in ChAT activity compared to young rats. General metabolic activity, measured by the 2-deoxyglucose method, was also decreased in the hippocampal CA1 and CA3 fields, the dentate gyrus, the medial septal-diagonal band area, and the prefrontal cortex of aged rats. There was a significant correlation between the decrease in glucose utilization and deficits on the Morris water maze. Most aged rats exhibit pathological EEG patterns as reflected by frequent long-duration high voltage neocortical spindles (HVS) during immobility. Bilateral lesions of the nucleus basalis and scopolamine treatment increased the incidence of HVS, thereby mimicking changes in the aged brain. We attempted to ameliorate the cognitive deficits observed in subgroups or impaired rats by either: (1) implanting fetal cells of basal forebrain origin into the hippocampus, or (2) infusing nerve growth factor (NGF) chronically into the lateral ventricle. The grafts appeared to facilitate an improvement in the ability of the impaired aged rats to perform in the Morris water maze. This improved performance was reversed by injections of atropine at doses that did not affect the behavior of young animals that performed well in the same task. These results suggest that enhancement of the cholinergic system could have an effect on the performance of the impaired aged animals. The study of the effects of infusions of NGF clearly demonstrate that the ability of impaired aged rats to remember what they had previously learned was increased after NGF treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

The effects of aging on hippocampal and cortical projections of the forebrain cholinergic system

It has been proposed that disruption of cholinergic input to the hippocampus and cortex contributes to the learning and memory deficits associated with aging. The data reviewed here, however, suggest that the oft-stated generalization that normal aging is characterized by disruption of cholinergic input to the hippocampus and cortex is not entirely correct. Instead it appears that age-related changes are not consistently found on measures such as the activity of ChAT or the content of ACh in these regions, basal levels of ACh release in cortex, and the number of cholinergic neurons in the basal forebrain (source of cholinergic input to the hippocampus and cortex). These observations suggest that unlike Alzheimer's disease, normal aging does not reliably produce a degeneration of the cholinergic innervation of the hippocampus and cortex. The responsivity of the cholinergic system, however, is altered during normal aging. ACh synthesis and stimulation-induced release of ACh are diminished in aged animals. Further, the electrophysiological response of postsynaptic neurons to ACh is reduced during aging. Although some regional differences in these age-related changes may be present, the generalization that the functioning of the cholinergic system is impaired during aging is probably accurate. Thus, investigation of these changes in the dynamic properties of cholinergic input to the hippocampus and cortex during aging may provide clarification of the relationship between cholinergic dysfunction and age-related decline in learning and memory and may also provide a more reasonable rationale for treatment approaches.

A visual recognition memory test for the assessment of cognitive function in aging and dementia

Young, non-demented elderly, and elderly demented subjects were administered a computerized visual recognition memory task. In the task, subjects were instructed to point out the new object from a group of objects whose number was progressively incremented. The test was subject-paced and made use of face-valid stimulus materials; it is closely comparable to tests developed for memory assessment in non-human primates that are sensitive to the effects of hippocampal ablation. The present task was found to elicit significant differences in performance between young and non-demented aged subjects, between the non-demented and demented elderly, and between demented subjects in the early and more advanced stages of senile dementia of the Alzheimer type (SDAT). In a discriminant analysis, the visual recognition memory test scores correctly classified 72.6% of the aged subjects and early SDAT patients. No significant difference in task performance was found between SDAT patients and demented patients with a significant cerebrovascular etiological component. Thus, although the task does not appear to be suitable for diagnostic purposes it would be useful for the assessment of treatment effects upon age-related cognitive dysfunction.

A quantitative morphometric analysis of the neuronal and synaptic content of the frontal and temporal cortex in patients with Alzheimer's disease

A quantitative morphometric analysis was used to estimate neurone and synapse densities in cerebral cortical biopsy tissues from patients with dementia under 65 years of age and pathologically verified as suffering from Alzheimer's disease. Estimates of the numerical density of neurones and synapses were made in layers II-III and V of both frontal and temporal cortex. A greater loss of synapses than that of neurones was found in Alzheimer's disease, amounting to a minimum (uncorrected for atrophy) of 25% in layers II-III and 36% in layer V of the temporal cortex, and 27% in layer V of the frontal cortex. Values of synapse to neurone ratio also demonstrated this greater loss of synapses, there being on average 38% fewer synapses associated with each surviving neurone in layers II-III of the temporal cortex, 30% fewer in layer V, and a deficit of 14% in layer V of the frontal cortex. It is concluded that a major loss of synapses occurred in this group of patients with Alzheimer's disease, probably at an early stage of the disease, and that the loss is likely to form a fundamental part of the pathological process that underlies the cortical damage of this condition.

Regional analysis of age-related changes in the cholinergic system of the hippocampal formation and basal forebrain of the rat

In an attempt to clarify conflicting reports of age-related changes in cholinergic systems of the rat hippocampal formation and basal forebrain, we compared aged (40 months) and adult (12 months) male rats using quantitative, regional receptor autoradiography in addition to radiolabelled assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). The activities of ChAT and AChE in Ammon's horn/subiculum are 24% and 38% lower, respectively, in the aged brains. There is also a drop in both ChAT (38%) and AChE (28%) activities in the septum, and a 46% drop in ChAT activity in the nucleus basalis of aged rats. In the septal pole of the hippocampal formation there is no significant change with age in binding of the muscarinic antagonist, tritiated quinuclidinyl benzylate (3H-QNB) in any hippocampal subregion. However, specific binding in the temporal pole is higher in the subiculum (40%), CA (27%), and dentate gyrus (25%) of the aged animals. Because some of the neurons of the diagonal band of Broca project to the temporal areas of the hippocampal formation by way of a ventral pathway, it is possible that with age this septohippocampal pathway is selectively affected. Particularly in Ammon's horn and the subicular regions of the aged rat hippocampus, postsynaptic muscarinic receptors may upregulate to compensate for decreases in presynaptic cholinergic activity.

Monoaminergic innervation of the frontal and temporal lobes in Alzheimer's disease

Seven markers of ascending (corticopetal) dopaminergic, noradrenergic and serotonergic neurones and choline acetyltransferase activity have been studied postmortem in frontal and temporal cortex from subjects with Alzheimer's disease and compared with a matched group of controls. Dopaminergic neurones (concentrations of dopamine, dihydroxyphenylacetic acid and homovanillic acid) were not deficient but some markers of the other neurones were affected. Noradrenaline and serotonin concentrations were reduced whereas the concentrations of their metabolites were either unaltered (5-hydroxyindoleacetic acid) or increased (3-methoxy-4-hydroxyphenylglycol). All deficits were most pronounced in the temporal cortex. Severely demented subjects had evidence of generalized neuronal loss, whereas those with moderate dementia showed significant loss of only choline acetyltransferase activity. In Alzheimer subjects, a significant relationship (inverse) was found between 5-hydroxyindoleacetic acid concentration and the number of neurofibrillary tangles.

Qualitative abnormalities of choline acetyltransferase in Alzheimer type dementia

The maximum activity of choline acetyltransferase (ChAT), the affinity for choline or acetyl-CoA and the isozyme pattern in the cerebral cortex of 5 cases of Alzheimer type dementia (ATD) and 6 age-matched control subjects were examined post-mortem. Maximum activities of ChAT were estimated in 5 cerebral cortical areas of Brodmann: 4, 7, 10, 17 and 22. A significant reduction in maximum activities of ChAT was found in all cortical areas for the cases of ATD. The affinity for choline or acetyl-CoA was measured in the frontal cortex (Brodmann's areas 4 and 6) and in the temporal cortex (Brodmann's areas 21 and 22). The affinity was significantly decreased in both cortices of demented patients. A significant correlation was observed between maximum activity of ChAT and the affinity for choline or acetyl-CoA. The isozyme pattern obtained by column chromatography on Sephadex G-200 was similar to that obtained by centrifugation on a sucrose density gradient. The isozyme pattern of ATD was different from that of the control subjects. These results suggest qualitative as well as quantitative abnormalities in the ChAT in autopsied brains of ATD.

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.

Neuropeptides in neurological disease

Neuropeptides are widely distributed in the central nervous system, where they serve as neuroregulators. Recent interest has focused on their role in degenerative neurological diseases. We describe the normal anatomy of neuropeptides in both the cerebral cortex and basal ganglia as a framework for interpreting neuropeptide alterations in Alzheimer's disease (AD), Huntington's disease, and Parkinson's disease. Concentrations of cortical somatostatin are reduced in AD and in dementia associated with Parkinson's disease. Concentrations of neuropeptide Y and corticotropin-releasing factor are also reduced in AD cerebral cortex. The reduced cortical concentrations of somatostatin and neuropeptide Y in AD cerebral cortex may reflect a loss of neurons or terminals in which these two peptides are co-localized. In Huntington's disease, basal ganglia neurons in which somatostatin and neuropeptide Y are co-localized are selectively preserved. Cerebrospinal fluid concentrations of neuropeptides in AD reflect alterations in cortical concentrations. Improved understanding of neuropeptides in degenerative neurological illnesses will help define which neuronal populations are specifically vulnerable to the pathological processes, and this could lead to improved therapy.

Neurofibrillary degeneration of cholinergic and noncholinergic neurons of the basal forebrain in Alzheimer's disease

Two principal features of Alzheimer's disease (AD) are (1) the occurrence of neurofibrillary tangles (NFTs) and senile plaques, and (2) the loss of cortical cholinergic activity because of dysfunction of neurons in the basal forebrain cholinergic system. The relationship of these two abnormalities is an unresolved issue in the pathology of AD. We used polyclonal antibodies specific for paired helical filaments (PHFs), combined with acetylcholinesterase (AChE) histochemistry, to assess the cytoskeletal changes of cholinergic and noncholinergic neurons in the basal forebrain in AD. In both sporadic and familial AD, the nucleus basalis of Meynert (nbM) showed a marked decrease in AChE-positive (AChE+) perikarya and abundant immunoreactive NFTs. In double-labeling studies of the nbM, PHF reactivity was found both in surviving AChE+ neurons and in many AChE- NFTs that were not associated with microscopically recognizable cell structures. Some surviving AChE+ perikarya did not contain NFTs. Numerous NFTs and senile plaques were identified by PHF immunoreactivity in other basal forebrain areas, including subnuclei of the amygdala that showed low or absent AChE activity. We conclude that the dysfunction and death of cholinergic neurons in the nbM is associated with extensive NFT formation, including apparently residual NFTs in loci where nbM neurons once existed; and many noncholinergic neurons and neurites in the basal forebrain show NFT and senile plaque formation. The cytopathology of AD involves neurons of varying transmitter specificities, including cholinergic neurons in the basal forebrain.

The selectivity of the reduction of serotonin S2 receptors in Alzheimer-type dementia

The high-affinity binding of thirteen ligands to putative neurotransmitter receptors was studied in temporal cortex of control and Alzheimer-type dementia (ATD) patients. A selective reduction of serotonin S2 receptors was observed in the ATD patients, to 57% of controls with no change in S1 receptors. Of the other ligand binding sites studied, only 3H-flunitrazepam binding was significantly reduced, to 84% of controls. Ligand binding sites which were unchanged in ATD temporal cortex included those labelled by adrenergic, adenosine, histamine, opiate, GABA, benzodiazepine and cholinergic ligands.

Somatostatin immunoreactivity in cortical and some subcortical regions in Alzheimer's disease

Reverse phase HPLC analysis of somatostatin immunoreactivity in the cerebral cortex in elderly normal individuals revealed that the majority of the immunoreactivity co-eluted with synthetic somatostatin-14. While an immunoreactive peak corresponding to somatostatin-28 was not detected there was a peak of immunoreactivity which eluted after somatostatin-14. In cases of senile dementia of Alzheimer type (SDAT), where abundant neurofibrillary tangles and senile plaques (density greater than 30 per 1.3-mm2 field) were present in the cerebral cortex, somatostatin immunoreactivity was found to be significantly decreased in either the frontal or temporal cortex. Chromatographic analysis, however, revealed that both the major immunoreactive peaks detected in the normal group were reduced in SDAT in the temporal and frontal cortex. Using a punch microdissection technique somatostatin immunoreactivity has been assessed in the nucleus of Meynert and amygdala of SDAT and elderly normal cases. While there was no change in somatostatin immunoreactivity in the nucleus of Meynert in the SDAT group, tissue punches taken from the amygdala revealed a selective decrease in somatostatin immunoreactivity in the basal nucleus, in the SDAT cases.

Somatostatin-like immunoreactivity within neuritic plaques

Alzheimer's disease or senile dementia of the Alzheimer type (SDAT) is a progressive neurodegenerative disease that is characterized pathologically by two types of microscopic lesions in the neocortex: the neurofibrillary tangle and neuritic plaque. The concentration of neuritic plaques is correlated with significant reductions in the level of specific neurotransmitter and neuropeptide systems in autopsied brains of patients with SDAT, including decreased amounts of the tetradecapeptide, somatostatin. The clinical effects of reduced cortical somatostatin activity in patients with SDAT is unclear, nor is it known whether somatostatinergic neurons participate in either lesion. In the present study we employed light microscopic immunocytochemistry to determine whether somatostatin-containing neurons participate in the formation of neuritic plaques. Examination of selected cortical regions from autopsied brains revealed 20-50% of all neuritic plaques contained somatostatin-positive profiles indicating that processes of somatostatinergic neurons are associated with neuritic plaque formation.

Neural transplantation: a review of recent developments and potential applications to the aged brain

Mammalian neural transplantation has recently been recognized to be a valuable technique for studying normal development and regeneration in the central nervous system. In addition, the ability of grafted neurons to reinnervate damaged regions of the host brain and to ameliorate some neuroendocrine deficits, cognitive disorders and motoric dysfunctions in young adult rodents has suggested that transplantation therapy may be effective in treating human neurodegenerative diseases and neurotransmitter deficiencies related to aging. It is of particular interest that initial studies of neuron transplants in aged rodents indicate that cholinergic, dopaminergic and noradrenergic neurons all integrate to some extent with the aged brain, and that the product of this graft-host interaction is improved behavioral performance of aged subjects. The present paper critically reviews the present domain of neural transplantation, its application to studies on the properties of the aged mammalian brain and discusses the possible therapeutic use of transplants in ameliorating transmitter-specific abnormalities associated with Parkinson's disease and Alzheimer's disease.

Memory function and brain biochemistry in normal aging and in senile dementia

One might argue that the decrease in the number of brain cells as a function of age could be the source of the functional age deficits in memory performance. However, this possibility seems less likely since the actual loss of neurons up to advanced age is relatively small. There are no good estimates of the loss of synapses. Golgi staining of cortical neurons would indicate that there is a loss with higher age. So far, however, the most convincing data of marked loss with age appear at the biochemical level. Most human data fail to demonstrate a decrease in cholinergic and serotonergic activity as a function of normal aging, although there is a loss of corresponding receptors. In AD/SDAT, however, there is a marked damage to these systems. Conceivably, acetylcholine may be providing informational rather than tone setting or balancing influence on memory function. This may explain the failure of cholinomimetic drugs to improve memory in AD/SDAT due to their inability to supply the informational properties of normal neuronal transmission. The catecholamines, noradrenaline and dopamine are both lost in normal aging and to a much higher degree in AD/SDAT. Animal data show that noradrenaline deficiency results in scattered attention. Such a pattern might also exist in the intact aged and through guidance by means of instructions, contextual cues, and a richer TBR information, the elderly are being forced to attend. This may promote and supersede the normal functions of the noradrenaline system by directions from external rather than internal influences, conceivably by potentiating the remaining noradrenaline neurons. The cortical motor areas are relatively spared from neuro-degenerative changes in normal aging and in AD/SDAT and this might provide a neuroanatomical basis for the elderly's and mildly to moderately demented patients' success in memory performance when motor action is involved. The role of dopamine in motor function and its stability with age in hippocampus may also provide a neurochemical basis for the preservation of memory when the subjects are allowed to act physically during encoding.

Cholinergic modulation of memory in rats

Central cholinergic systems have long been implicated in the modulation of learning and memory processes in animals and man. Drugs that affect the central cholinergic system have been found either to enhance or to hinder performance in tests of learning and memory. Few studies have evaluated the effects of different cholinergic drugs within a single experimental paradigm and with a relatively wide dose range. The studies reported here investigated the effects of cholinergic drugs with diverse modes of action on the retention of a passive avoidance response. Physostigmine, arecoline, oxotremorine, nicotine, and 4-aminopyridine were administered IP immediately following the acquisition of a one-trial passive avoidance task. All of the drugs were found to enhance 72-h retention of passive avoidance; however, the effective doses were different for each of the drugs studied.

The aging human brain

Postmortem and computed tomographic studies demonstrate many anatomical, morphological, and neurochemical differences between brains of old and young human beings. The variability of the results is great, however, and brains of some old subjects have characteristics of brains of younger controls. Furthermore, important aspects of brain functional activity are not reduced in the elderly. These include resting cerebral oxidative metabolism and "crystallized" intelligence as represented by verbal subtests on the Wechsler Adult Intelligence Scale. In the absence of superimposed disease (which frequently limits aging studies), overall function can be maintained at high and effective levels because of the plasticity and redundancy capabilities of the human brain.

Chromatographic characterization of neuropeptides in post mortem human brain

Reverse phase high performance liquid chromatography was used to establish the immunoreactive species of five neuropeptides (thyrotropin-releasing hormone, luteinising hormone-releasing hormone, neurotensin, substance-P and somatostatin) in three areas of post mortem human brain--the hypothalamus, amygdala and cortex. In the majority of cases the major immunoreactive peak corresponded to the authentic peptide, although other peaks of immunoreactivity were observed in several instances. It was established that somatostatin-14 was present as the major immunoreactive form and that somatostatin-28 did not occur in any of the three brain areas, although other somatostatin-immunoreactive peaks of unknown structure were detected. In addition to authentic neurotensin in the cortex, a substantial peak of immunoreactivity corresponding to the elution time of neurotensin (1-11) was observed. LH-RH was not detected in the amygdala, but was present in the cortex as a minor component of overall immunoreactivity. The major peak of substance-P immunoreactivity in all three brain areas corresponded to authentic substance-P; in addition immunoreactive material eluting in the region of [Met-O] substance-P, substance-P (5-11) and substance-P (6-11) were detected. TRH occurred as the major peak in all three areas, although minor peaks of immunoreactivity were seen in the amygdala.

Multiple changes in the sensitivity of cingulate cortical neurones to putative neurotransmitters in ageing rats: substance P, acetylcholine and noradrenaline

The responsiveness of neurones in the anterior cingulate cortex to iontophoretically applied substance P(SP), acetylcholine (ACh), noradrenaline (NA) and GABA was compared in young (3-4 months) and old (24-30 months) rats. Neurones in the old rats were less sensitive to the depressant effects of NA but not GABA. These cells were also less sensitive to the excitatory actions of ACh but markedly more sensitive to those of SP. Such changes in responsiveness could be involved in the deficits in cerebral function which often occur in old age.

Somatostatin-like immunoreactivity in lumbar cerebrospinal fluid from neurohistologically examined demented patients

The concentration of somatostatin-like immunoreactivity (SLI) in lumbar cerebrospinal fluid was measured in clinically suspected examples of either Alzheimer's disease (AD) or Pick's disease and controls. No significant correlation was found between the concentration of SLI and the age (22-73 years) of controls. Histological examination of brain material from the demented patients enabled the samples to be divided into AD and examples of clinically suspected AD or Pick's disease without specific histological change. The mean concentration of SLI was only slightly reduced in patients with AD in the presenium compared to control, and was unaltered from control in the examples of AD of senile age. The group of demented patients without specific histological change had a reduced concentration of SLI in lumbar CSF compared to control patients.

Intralaminar neurochemical distributions in human midtemporal cortex: comparison between Alzheimer's disease and the normal

The intralaminar distributions of transmitter and nontransmitter enzyme activities and amino acid levels were determined in the midtemporal cortices from normal individuals and established cases of Alzheimer's disease. In the normal, choline acetyltransferase (CAT) and acetylcholinesterase (AChE) activities were relatively high in the outer cortical layers, particularly, for CAT, in the two granular layers (II and IV). Both activities were reduced in Alzheimer's disease at all, although generally most extensively in the outer and middle layers of the grey matter whereas activities were near normal in the white matter. Further, the enzyme distribution patterns of these cholinergic activities were also disrupted in Alzheimer's disease and the activity of CAT throughout the cortex was generally reduced to that found in the white matter. No such differences in distribution were found for two other enzymes, pseudocholinesterase and lactate dehydrogenase. Assessment of the gamma-aminobutyric acid (GABA) system in the normal revealed a much more extensive intralaminar variation in the enzyme, glutamate decarboxylase, compared with the level of GABA itself. In contrast with the cholinergic enzymes, neither the levels nor intralaminar patterns of GABA were altered in Alzheimer's disease. From an analysis of free amino acids at the different cortical levels, the cortical pattern of glutamic acid in the normal was different from that for GABA, aspartic acid, or nontransmitter amino acids such as alanine. Neither of the putative amino acids, glutamate or aspartate, was altered in Alzheimer's disease. These findings demonstrate the relatively selective nature of microchemical changes occurring in the cortex in Alzheimer's disease and suggest that a functional abnormality in cholinergic input to the outer neocortical layers (I-IV) with predominantly receptive and associative functions may be an important feature of the disease.

Vasoactive intestinal peptide in cerebrospinal fluid

Immunoreactive vasoactive intestinal peptide (VIP) was measured in lumbar and ventricular cerebrospinal fluid (CSF) from patients with various neurological disorders and in 2 hour aliquots of cisternal fluid removed continuously from rhesus monkeys. Although most of the VIP in concentrated pools of human ventricular fluid and of monkey cisternal fluid co-eluted with synthetic porcine VIP28 on a column of Sephadex G-25 superfine, there was evidence that smaller immunoreactive fragments were also present. A circadian pattern of CSF VIP concentration was observed in 2 of the 3 monkeys studied, with highest levels occurring at night and lowest during the day. Ventricular fluid VIP levels were highest in hydrocephalic children and lowest in patients with multiple sclerosis or epilepsy, while VIP was not detectable in ventricular fluid from patients in coma following a severe head injury. There were no significant differences in VIP concentrations in CSF from patients with dystonia. Parkinson's disease, or Alzheimer's disease, suggesting that VIP containing neurons are not affected in these disorders. Lumbar fluid VIP levels were low in patients undergoing aneurysm surgery. Since VIP is a potent vasodilator, these findings may have important implications in relation to the development of vasospasm following subarachnoid hemorrhage.

Dopamine-beta-hydroxylase activities in serum and cerebrospinal fluid of aged and demented patients

Age-related changes in dopamine-beta-hydroxylase (DBH) activities in serum and cerebrospinal fluid (CSF) were determined. In normal subjects, serum DBH activity increased gradually from the 3rd to the 8th decade, but decreased prominently in the 9th decade. DBH activity in CSF did not differ between younger and older subjects. Serum DBH activity decreased significantly in senile dementia of Alzheimer's type (SDAT, 12.2 +/- 8.8 nmoles/min/ml, P less than 0.05), but not in multi-infarct dementia (MID, 13.9 +/- 9.1 nmoles/min/ml) compared to control subjects (17.1 +/- 9.5 nmoles/min/ml). The decrease of serum DBH in SDAT was more prominent in patients with severe dementia and/or severe brain atrophy. DBH activity in CSF was much lower than that in serum and did not correlate with each other. DBH activity in CSF obtained from SDAT patients (1.60 +/- 0.94 nmoles/h/ml) and from MID patients 2.01 +/- 0.99 nmoles/h/ml) were both lower than that from other neurological diseases without dementia (4.04 +/- 3.81 nmoles/h/ml). DBH in CSF from SDAT patients was significantly lower (P less than 0.05) than that from controls, but that from MID did not differ from controls. Noradrenergic nervous dysfunction is partly associated with pathophysiology and life expectancy of senile dementia of Alzheimer's type (SDAT).

Implications of neuropeptides in neurological diseases

Neuropeptides are sufficiently stable to allow valid radioimmunoassay of peptide concentrations in post-mortem human nervous tissue and in human cerebrospinal fluid. Studies have now documented abnormalities of peptide concentrations in degenerative diseases of the brain. Somatostatin concentration is reduced in the hippocampus and neocortex of patients dying with Alzheimer's type dementia. In Huntington's disease, there are reduced concentrations of substance P, met-enkephalin and cholecystokinin in the basal ganglia; in contrast the concentrations of somatostatin and TRH are increased. Immunocytochemical and experimental lesion studies are underway in an attempt to localize the peptide-containing cells affected by these disorders; and the potential role of alterations in neuropeptide function in the pathogenesis, clinical manifestations and therapy of these illnesses is of great interest. Although alterations of CSF peptide concentrations have been reported in a variety of human diseases, interpretation of these results requires knowledge of the origin and disposition of CSF peptides. Future research into the pathology of peptidergic systems will depend on the development of specific peptide antagonists to probe dynamic aspects of peptide function and on the application of the tools of molecular biology, such as specific mRNA assays, to human material.

A post-mortem comparison of the cortical cholinergic system in Alzheimer's disease and Pick's disease

Assessment of neurochemical markers in the frontal cortex indicates that choline acetyltransferase is significantly decreased in Alzheimer's and Gerstmann-Straussler dementias but not in Pick's dementia. It therefore appears that the cholinergic innervation of the cortex from the basal forebrain is intact in Pick's disease. Cortical somatostatin was decreased only in Alzheimer's disease (AD), indicating that loss of somatostatin is not a constant feature in different forms of dementia. Muscarinic binding sites were unaltered in Pick's disease and Gerstmann-Straussler syndrome but were decreased in a subpopulation of AD patients. These data suggest that in some cases of AD a significant loss of cholinoceptive neurones in the cortex is evident.

[3H]R05-4864 and [3H]flunitrazepam binding in kainate-lesioned rat striatum and in temporal cortex of brains from patients with senile dementia of the Alzheimer type

In agreement with other workers we report increased [3H]R05-4864 binding in kainate-lesioned rat striatum. [3H]R05-4864 binding, a possible glial marker, was also increased in temporal cortex obtained post-mortem from patients with Alzheimer's disease. [3H]Flunitrazepam binding was decreased in these brain samples, possibly indicative of neuronal cell loss. It is suggested that the poor binding characteristics of [3H]R05-4864 in human brain samples may limit its usefulness in assessing gliosis.

Neocortical substance P neurons in the baboon: an immunohistochemical finding

Substance P-like immunoreactive (SP-LI) neurons have been demonstrated, by an avidin-biotin immunohistochemical method, in several neocortical areas in the brains of baboons. These neurons are mostly small in size, and are of many different somatic shapes, including bipolar and multipolar types. They occur in laminae III-VI but are most common in laminae V and VI. It is postulated that these neurons could contribute to previously-described cortical SP-LI fiber networks.

Human brain neurochemistry - some postmortem problems

Neurochemical analyses of postmortem human brain tissue is currently a challenging and expanding area of research. Many groups are now concentrating on mapping central neuronal pathways or identifying biochemical abnormalities in neurological and psychiatric diseases. In investigations of this kind a number of more or less obvious problems have to be tackled and this article provides some idea of current, and often controversial, issues associated with sampling postmortem brain material and with some of the variable factors which may influence neurochemical data.

Cholecystokinin in the central nervous system: a minireview

This review focuses on the structure, distribution, neuronal pathways, receptor binding, release, biosynthesis and degradation of CCK in the central nervous system. Other aspects of the isolation and chemistry of CCK (1), its role in satiety (2), as a hormone or neurotransmitter (3,4), and its evolution (5) have been reviewed recently.

Alzheimer's disease: choline acetyltransferase activity in brain tissue from clinical and pathological subgroups

Choline acetyltransferase activity was measured postmortem in five brain regions to determine if such activity provided biochemical support for clinical and pathological subgrouping of Alzheimer's disease. Seven patients with Alzheimer's disease were divided into groups based on age at onset, severity of neuropathological changes, history of myoclonus, family history of dementia, cerebellar amyloid plaques, and congophilic angiopathy. Thirty-two age-matched normal control subjects and 17 neurological control patients with Huntington's disease were also studied. Patients with early-onset and late-onset Alzheimer's disease did not differ in the clinical duration of their disease. Choline acetyltransferase activity was significantly lower in patients with early-onset Alzheimer's disease than in age-matched control subjects in frontal cortex, temporal cortex, hippocampus, and cerebellum. In contrast, choline acetyltransferase activity in patients with late-onset Alzheimer's disease was significantly lower than in age-matched control subjects only in hippocampus. There was a tendency for choline acetyltransferase activity to be lower in cortex from patients with early-onset Alzheimer's disease compared with cortex from the late-onset group, and this difference was significant in temporal cortex. Choline acetyltransferase activity was also measured in the substantia innominata from 9 patients with Alzheimer's disease and 5 age-matched control subjects. Subjects with early-onset Alzheimer's disease had significantly lower choline acetyltransferase activity in substantia innominata than did control subjects. Patients with Alzheimer's disease and a history of myoclonus had significantly lower choline acetyltransferase activity than did affected patients without myoclonus. Multivariate regression analysis showed myoclonus to be the single best predictor of low brain choline acetyltransferase activity. These results provide further evidence for clinical, pathological, and biochemical heterogeneity in Alzheimer's disease.

The neurochemistry of Alzheimer's disease and senile dementia

At this time we seem to be on the verge of opening two new fields of research on Alzheimer's disease. To treat the symptoms of this condition, an understanding of the factors regulating acetylcholine synthesis will be very important. Because of the vast amount of work on this neurotransmitter over the last 30 years, rapid progress in this area should be made. However, to truely conquer Alzheimer's disease, we need to learn what it is that attacks and apparently destroys the cholinergic neurons. While this second point may take a little more time to unravel, the work will be both exciting and very worth while.

The distribution of cholecystokinin and vasoactive intestinal peptide in rhesus monkey brain as determined by radioimmunoassay

The concentration of cholecystokinin (CCK) and vasoactive intestinal peptide (VIP) in dissected cortical and subcortical areas of four rhesus monkeys' brains was determined by radioimmunoassay (RIA). Cerebral cortical samples from one human brain are included for comparison. Preliminary data from two baboon brains are described. The results are similar to previous studies on rat (1-7), human (7-12), porcine (12,13), bovine (3) and guinea pig brains (14) and indicate that: 1) both CCK and VIP are widely distributed in cortical and subcortical areas in these species, 2) CCK is generally more abundant than VIP in primate brain, and 3) the distribution of CCK and VIP in the rat brain parallel those in infrahuman primate and human brain.

Cortical neuronal counts in normal elderly controls and demented patients

The purposes of the investigation were to determine whether there was significant neuronal loss in dementia, and if so, whether it was general or localised, and to examine the relationship between neuronal counts, senile plaques and neurofibrillary change. Neuronal counts were made in nine cortical areas in the brains of 25 patients with senile dementia of the Alzheimer type and twenty-five age-matched controls, with the aid of an image analysing computer. Neuronal counts per square millimetre were significantly lower in the demented group of patients in the inferior frontal and superior temporal gyri. Neuronal counts in four columns of cortex were significantly reduced in superior, middle and inferior frontal gyri, cingulate gyrus and superior and middle temporal gyri. There was no significant difference in the parietal (Brodmann area 7) or occipital (Brodmann area 17) cortex. Corresponding glial counts per square millimetre show a significant increase in the demented group only in the middle and inferior temporal gyri. Neuronal counts correlated weakly but significantly with plaque counts in the same cortical area in the middle frontal gyrus and the superior and middle temporal gyri. High correlations between neuronal counts and estimates of neurofibrillary change were found in superior, middle and inferior frontal gyri, cingulate gyrus and superior and middle temporal gyri.

Muscarinic receptor compensation in hippocampus of Alzheimer patients

The activity of the acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) (presynaptic marker) and number of muscarine-like receptor binding sites have been measured in the hippocampus from eight individuals with senile dementia of Alzheimer type (SDAT) and ten controls. A negative correlation (r = 0.80; p less than 0.05) was found between the ChAT activity and the number of muscarine-like receptors in the SDAT group but not in the controls. The findings might indicate an ongoing compensatory receptor mechanism as a response to changes in presynaptic cholinergic activity.

Some enkephalin- or VIP-immunoreactive hippocampal pyramidal cells contain neurofibrillary tangles in the brains of aged humans and persons with Alzheimer's disease

Neurofibrillary tangles are one of the histopathological neuronal abnormalities present in normal aging and especially in Alzheimer's Disease. We have utilized immunocytochemical staining for neuropeptides followed by Congo red with gallocyanin counterstaining and polarized illumination to determine whether enkephalin (Enk), somatostatin (Som), cholecystokinin (CCK), or vasoactive intestinal polypeptide (VIP) are contained in neurons afflicted with such tangles. A few Enk- or VIP-immunoreactive pyramidal cells in field hl and subiculum were found to contain tangles. Many such Enk- or VIP-immunoreactive neurons and cells containing Som- or CCK-like immunoreactivity did not contain such tangles.