Decreased somatostatin-like immunoreactivity in cerebral cortex and cerebrospinal fluid in Alzheimer's disease

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

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

Distinct modulation of microglial amyloid β phagocytosis and migration by neuropeptides (i)

Microglial activation plays an integral role in the development and course of neurodegeneration. Although neuropeptides such as bradykinin (BK), somatostatin (SST), and endothelin (ET) are known to be important mediators of inflammation in the periphery, evidence of a similar function in brain is scarce. Using immunocytochemistry, we demonstrate the expression of receptors for BK (B1, B2 subtypes), ET (ETA, ETB subtypes) and SST (SST 2, 3, 4 subtypes) in primary microglia and microglial cell lines. Exposure of BV2 and N9, as well as primary microglial cells to BK or SST increased Aβ uptake in a concentration-dependent manner, whereas endothelin decreased Aβ uptake. This was caused by increased phagocytosis of Aβ since the rate of intracellular Aβ degradation remained unaffected. All neuropeptides increased chemotactic activity of microglia. In addition, BK reduced Aβ-induced expression of proinflammatory genes including iNOS and COX-2. ET decreased the Aβ-induced expression of monocyte chemoattractant protein 1 and interleukin-6. These results suggest that neuropeptides play an important role in chemotaxis and Aβ clearance and modulate the brain's response to neuroinflammatory processes.

Effects of insulin and octreotide on memory and growth hormone in Alzheimer's disease

Both insulin alone and the somatostatin analogue octreotide alone facilitate memory in patients with Alzheimer's disease (AD). Since octreotide inhibits endogenous insulin secretion, the cognitive effects of insulin and octreotide may not be independent. This study tested the individual and interactive effects of insulin and octreotide on memory and plasma growth hormone (GH) levels in older adults. Participants were 16 memory-impaired (AD = 7, amnestic mild cognitive impairment = 9; apolipoprotein E [APOE] epsilon4- [no epsilon4 alleles] = 9, epsilon4+ [1-2 epsilon4 alleles] = 7), and 19 cognitively-intact older adults (APOE epsilon4- = 17, epsilon4+ = 1). On separate days, fasting participants received counterbalanced infusions of: 1) insulin (1 mU.kg(-1).min(-1)) and dextrose to maintain euglycemia; 2) octreotide (150 microg/h); 3) insulin, dextrose, and octreotide; or 4) saline. Story recall was the principal endpoint. Insulin alone facilitated delayed recall for epsilon4- patients, relative to epsilon4+ patients (P = 0.0012). Furthermore, epsilon4- patients with higher Mattis Dementia Rating Scale (DRS) scores had greater octreotide-induced memory facilitation (P = 0.0298). For healthy adults, octreotide facilitated memory (P = 0.0122). Unexpectedly, hyperinsulinemia with euglycemia increased GH levels in healthy controls (P = 0.0299). Thus, insulin and octreotide appear to regulate memory in older adults. APOE epsilon4 genotype modulates responses to insulin and octreotide. Finally, insulin may regulate GH levels during euglycemia.

Chronic but not acute intracerebroventricular administration of amyloid beta-peptide(25-35) decreases somatostatin content, adenylate cyclase activity, somatostatin-induced inhibition of adenylate cyclase activity, and adenylate cyclase I levels in the rat hippocampus

Although alterations in adenylate cyclase (AC) activity and somatostatin (SRIF) receptor density have been reported in Alzheimer's disease, the effects of amyloid beta-peptide (Abeta) on these parameters in the hippocampus are unknown. Our aim was to investigate whether the peptide fragment Abeta(25-35) can affect the somatostatinergic system in the rat hippocampus. Hence, Abeta(25-35) was injected intracerebroventricularly (i.c.v.) to Wistar rats in a single dose or infused via an osmotic minipump connected to a cannula implanted in the right lateral ventricle during 14 days. The animals were decapitated 7 or 14 days after the single injection and 14 days after chronic infusion of the peptide. Chronic i.c.v. infusion of Abeta(25-35) decreased SRIF-like immunoreactive content without modifying the SRIF receptor density, SRIF receptor expression, or the Gialpha(1), Gialpha(2), and Gialpha(3) protein levels in the hippocampus. This treatment, however, caused a decrease in basal and forskolin-stimulated AC activity as well as in the capacity of SRIF to inhibit AC activity. Furthermore, the protein levels of the neural-specific AC type I were significantly decreased in the hippocampus of the treated rats, whereas an increase in the levels of AC V/VI was found, with no alterations in type VIII AC. A single i.c.v. dose of Abeta(25-35) exerted no effect on SRIF content or SRIF receptors but induced a slight decrease in forskolin-stimulated AC activity and its inhibition by SRIF. Because chronic Abeta(25-35) infusion impairs learning and memory whereas SRIF facilitates these functions, the alterations described here might be physiologically important given the decreased cognitive behavior previously reported in Abeta-treated rats.

The proprotein convertase PC2 is involved in the maturation of prosomatostatin to somatostatin-14 but not in the somatostatin deficit in Alzheimer's disease

A somatostatin deficit occurs in the cerebral cortex of Alzheimer's disease patients without a major loss in somatostatin-containing neurons. This deficit could be related to a reduction in the rate of proteolytic processing of peptide precursors. Since the two proprotein convertases (PC)1 and PC2 are responsible for the processing of neuropeptide precursors directed to the regulated secretory pathway, we examined whether they are involved first in the proteolytic processing of prosomatostatin in mouse and human brain and secondly in somatostatin defect associated with Alzheimer's disease. By size exclusion chromatography, the cleavage of prosomatostatin to somatostatin-14 is almost totally abolished in the cortex of PC2 null mice, while the proportions of prosomatostatin and somatostatin-28 are increased. By immunohistochemistry, PC1 and PC2 were localized in many neuronal elements in human frontal and temporal cortex. The convertases levels were quantified by Western blot, as well as the protein 7B2 which is required for the production of active PC2. No significant change in PC1 levels was observed in Alzheimer's disease. In contrast, a marked decrease in the ratio of the PC2 precursor to the total enzymatic pool was observed in the frontal cortex of Alzheimer patients. This decrease coincides with an increase in the binding protein 7B2. However, the content and enzymatic activity of the PC2 mature form were similar in Alzheimer patients and controls. Therefore, the cortical somatostatin defect is not due to convertase alteration occuring during Alzheimer's disease. Further studies will be needed to assess the mechanisms involved in somatostatin deficiency in Alzheimer's disease.

Cholinergic deafferentation exacerbates seizure-induced loss of somatostatin-immunoreactive neurons in the rat hippocampus

The loss of somatostatin-immunoreactive neurons and the sprouting of mossy fibers are typical histopathological abnormalities in the hippocampus in experimental and human temporal lobe epilepsy. To investigate whether the development of seizure-induced alterations is regulated by the subcortical afferent pathways to the hippocampus, we lesioned cholinergic, noradrenergic or serotonergic afferent pathways in rats two days after seizures were induced with kainate. Two months later, somatostatin-immunoreactive neurons were counted in the hilus to assess the severity of neuronal damage. Mossy fiber sprouting was analysed from adjacent Timm-stained sections. Kainate-induced seizures caused a loss of hilar somatostatin-immunoreactive neurons in the septal end of the hippocampus, where 63% of the somatostatin-immunoreactive neurons survived. Even more severe damage was found in the temporal end of the hippocampus (only 21% surviving). Cholinergic deafferentation of the hippocampus (using 192-IgG saporin) decreased the overall number of hilar somatostatin-immunoreactive neurons. In control rats that did not receive kainate, 87% (septal end) and 74% (temporal end) of the hilar somatostatin-immunoreactive neurons remained after cholinergic deafferentation. Moreover, seizure-induced damage to hilar somatostatin-immunoreactive neurons was further exacerbated by 192-IgG-saporin, with only 35% of the neurons remaining in the septal end and 14% in the temporal end of the hippocampus. Noradrenergic [using N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine] or serotonergic (using 5,7-dihydroxytryptamine) lesions did not affect the number of hilar somatostatin-immunoreactive neurons either in control or in kainate-treated rats. The severity and distribution of seizure-induced mossy fiber sprouting were also not affected by any of the lesions. These data suggest that various subcortical afferent pathways may differentially modulate seizure-induced damage to the hippocampus. Damage to cholinergic neurons results in the loss of hilar somatostatin-immunoreactive neurons and exacerbates the seizure-induced loss of somatostatin-immunoreactive neurons.

Beta-adrenergic dysfunction exacerbates impairment of working memory induced by hippocampal NMDA receptor blockade in rats

To clarify the interactions between hippocampal glutamatergic and adrenergic systems in the working memory function of rats, the effects of hippocampal NMDA receptor blockade combined with noradrenaline depletion or alpha- and beta-adrenoceptor blockade on this behavior were examined with a three-panel runway task. Intrahippocampal administration of the potent and competitive NMDA receptor antagonist (+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) at a dose of 32 ng/side significantly increased the number of errors (attempts to pass through two incorrect panels of the three panels gates at four choice points) in the working memory task, whereas the 3.2 ng/side dose of CPP did not affect working memory errors. Administration of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2 -bromobenzylamine (DSP-4) at 50 mg/kg i.p. produced marked reductions in hippocampal and cortical noradrenaline contents, but it had no effect on working memory errors. Intrahippocampal administration of 3.2 ng/side CPP, the behaviorally ineffective dose in intact rats, significantly increased the number of working memory errors in the noradrenaline-depleted rats. The alpha-adrenoceptor antagonist phentolamine (3.2 mg/kg i.p.) did not affect working memory errors whether administered alone or in combination with intrahippocampal CPP (3.2 ng/side). The beta-adrenoceptor antagonist propranolol (10 mg/kg i.p.) also had no effect on working memory errors. However, propranolol (10 mg/kg) produced a significant increase in working memory errors when administered together with intrahippocampal CPP (3.2 ng/side). These results suggest that hippocampal NMDA/beta-adrenergic interactions are involved in neural processes mediating working memory function of rats.

The neurochemistry of Alzheimer type, vascular type and mixed type dementias compared

We present the results of a meta-analysis of neurochemical changes in human post mortem brains of Alzheimer type (AD), vascular type (VD) and mixed type (MF) dementias, and matched controls based on 275 articles published between January 1980 and February 1994. Severity of degeneration between the different neurochemical systems is as follows, although ranking is difficult with regard to limited numbers of investigations in some neurochemical systems: Cholinergic system > serotonergic system > excitatory amino acids > GABAergic system > energy metabolism > NA > oxidative stress parameters > neuropeptides > DA. But, within a neurochemical system, degeneration is not evenly distributed. Spared parameters, e.g. muscarinic receptors and MAO-B, allow to make some suggestions for future therapeutic strategies.

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

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

Differential correlation between neurochemical deficits, neuropathology, and cognitive status in Alzheimer's disease

The relationships between neurofibrillary tangles (NFT), senile plaques (SP), and the deficits in somatostatin (SRIH) and choline acetyltransferase (ChAT) levels were determined in Brodmann area 9, 40, 22, and 17/18 in 12 women whose Blessed test score (BTS) ranged from 27 to 1. NFT density correlated with the cognitive decline in areas 9, 40, and 22 and with SP number in area 22 and 17/18. ChAT levels were linked to the BTS in area 9, 40, and 22 and SRIH levels in area 9 only. ChAT, but not SRIH, did correlate with SP (area 22) and NFT (area 40 and 22). Decreases in ChAT and SRIH were correlated in areas 9 and 22. These results indicate that the somatostatinergic deficit in Alzheimer's disease is more regionally restricted than the cholinergic one. The correlation between SRIH and ChAT as observed in area 9 and 22 may indicate that somatostatin- and acetylcholine-containing elements in the frontal and temporal lobes are particularly relevant to the cognitive decline as observed in Alzheimer's disease.

A critique of instruments and methods to detect, diagnose, and rate delirium

This document reviews existing instruments for evaluation of delirium. Instruments have been grouped into four categories: tests that screen for cognitive impairment, delirium diagnostic instruments, delirium-specific numerical rating scales, and laboratory and paraclinical exams. Analysis of instruments was based on comparison of their psychometric properties as well as subjective judgment. Guidelines are suggested for choosing the appropriate instrument according to the type of clinical evaluation or delirium research envisaged. Important factors in choosing an instrument, besides the appropriateness of its psychometric characteristics, include administration time constraints, level of rater expertise, and patient capabilities. By familiarizing investigators with the variety of evaluation instruments available, this work should permit more appropriate instrument selection in future studies on delirium.

Neuropeptide Y immunoreactive neurons in murine trisomy 16 cortical cultures. Plasticity of expression and differentiation

Neuropeptide Y (NPY)-containing neurons are depleted in the cortices of individuals with Alzheimer disease (AD), yet spared in the striatum of patients with Huntington chorea. It is unknown whether this neuronal phenotype is inherently susceptible to the neurodegenerative processes that are a hallmark of AD. To study this question, the murine trisomy 16 model of Down syndrome and Alzheimer disease was investigated. Since trisomic fetuses die in utero, studies were carried out on primary cultures of dissociated cortical neurons. These were prepared from 15-d gestational trisomy 16 fetuses and their littermate euploid controls, and examined by immunocytochemical staining for neuropeptide Y at 7 and 12 d in vitro. Trisomy 16 neurons were also grown on euploid glial carpets, whereas euploid neurons were grown on trisomic glia. The results demonstrate a significant increase in the number of NPY neurons and a stunting in the dendritic arbor of these neurons in trisomic vs euploid cortex. Both of these parameters could be normalized by direct contact with euploid glia. When euploid cortex was plated on trisomic glia, the number of NPY neurons and their morphology were altered so that they began to resemble trisomic NPY cortical neurons. These results indicate a dysregulation of NPY neuronal expression and differentiation in trisomy 16 cortex that are modifiable by interaction with euploid glia and imply an abnormal trophic (glial) environment in trisomic cortex.

Cortical and subcortical neuropeptides in Alzheimer's disease

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

A long-term follow-up study of cerebrospinal fluid somatostatin in delirium

Cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for elderly delirious patients during the acute stage and after 1- and 4-year follow-up periods, and the SLI levels were compared with age-equivalent controls. As a whole group, and also when the group was subdivided according to the severity of cognitive decline at the acute stage, type of delirium or the central nervous system disease, delirious patients showed significant reduction of SLI as compared with the controls. In the follow-up, we observed a further reduction of CSF SLI together with significant correlations in the second, third and fourth samples between SLI levels and Mini-Mental State Examination scores. Our results suggest a role for somatostatinergic dysfunction in the genesis of some symptoms of delirium, and this dysfunction may be linked to the long-term prognosis of delirious patients.

Cultured GABA-immunoreactive neurons are resistant to toxicity induced by beta-amyloid

Neurodegeneration in Alzheimer's disease is characterized by a selective loss of particular cell populations. Several recent lines of evidence suggest that beta-amyloid protein directly contributes to the disease's progression and is likely responsible for the observed pattern of neuronal death. We have previously demonstrated that aggregated beta-amyloid peptides are neurotoxic to cultured neurons. We now report that a neuronal population exhibiting GABA-immunoreactivity is resistant to beta-amyloid-induced toxicity in vitro, a finding consistent with observations in the Alzheimer brain. Determination of the intrinsic neuronal characteristics responsible for resistance to beta-amyloid may prove beneficial in both understanding the mechanism(s) of beta-amyloid neurotoxicity and halting the disease's progressive neuronal degeneration.

Working memory deficits following muscarinic blockade combined with depletion of brain somatostatin in rats

In a working memory task with three-panel runway paradigm, cysteamine, a depletor of somatostatin, at 100 or 200 mg/kg i.p. given 24 h before testing, had no effect on the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points). Cysteamine at 100 mg/kg caused a significant reduction in somatostatin-like immunoreactivity in the rat brain, including the hippocampus and cerebral cortex. Working memory errors were significantly increased by scopolamine, a muscarinic receptor antagonist, at 0.32 mg/kg i.p. given 20 min before testing, whereas errors were not affected by the 0.1 mg/kg dose. Combined administration of 100 mg/kg cysteamine and 0.1 mg/kg scopolamine significantly increased the number of working memory errors. However, cysteamine at 100 mg/kg and scopolamine at 0.1 mg/kg had no effect on reference memory errors, whether they were administered alone or in combination. These results suggest that depletion of brain somatostatin aggravates working memory deficits induced by blockade of muscarinic receptors.

Peptide histidine methionine in cerebrospinal fluid of patients with senile dementia of the Alzheimer type

Immunoreactivities (IRs) of peptide histidine methionine (PHM) as well as somatostatin and vasoactive intestinal peptide (VIP) in the cerebrospinal fluid (CSF) were measured in patients with senile dementia of the Alzheimer type (SDAT) and age-matched control subjects. We found statistically significant reductions in the PHM-IR and somatostatin-IR levels in the CSF from patients with SDAT, as compared with those of the controls. However, the VIP-IR level in the CSF from SDAT was not different from that of the controls. These results suggest that selective degeneration of neurons containing somatostatin and PHM or the alteration in metabolism of PHM in the CSF might occur in SDAT.

Facilitation of 2-deoxyglucose uptake in rat cortex and hippocampus slices by somatostatin is independent of cholinergic activity

2-Deoxyglucose (2-DG) uptake is an index of regional glucose utilization which reflects predominantly activity in the axonal terminal of neuronal pathways. The present experiments showed that somatostatin elevated 2-DG uptake in rat cortex and hippocampus slices. Treatment with somatostatin-14 and somatostatin-28 markedly enhanced 2-DG uptake, whereas the amino-terminal fragment of somatostatin-28 did so only slightly. This effect appeared to be mediated by an interaction with somatostatin receptors because cyclo-somatostatin, a somatostatin antagonist, abolished the effect of somatostatin-14. The increase in 2-DG uptake caused by somatostatin-14 was blocked by the calcium channel antagonist, nifedipine, but not by tetrodotoxin, suggesting that the action of somatostatin does not require the initiation of impulse activity, somatostatin enhanced the KCl-induced release of acetylcholine, suggesting that a cholinergic mechanism is involved in the somatostatin-induced cellular responses. We therefore examined whether acetylcholine receptor antagonists block the somatostatin-induced increase in 2-DG uptake. Neither muscarinic nor nicotinic receptor antagonists affected the somatostatin-14-induced response. The present results suggest that somatostatin has a stimulatory effect on energy metabolism and that this effect is independent of acetylcholine receptor mechanism.

Somatostatin in the cerebrospinal fluid of schizophrenic patients before and after neuroleptic drug treatment

A radioimmunoassay procedure was used to determine levels of somatostatin-like immunoreactivity in cerebrospinal fluid obtained from 9 schizophrenic patients, 7 patients with other psychiatric disorders, and 10 nonpsychiatric surgical controls. There were no significant differences in mean somatostatin baseline levels between the schizophrenic, nonschizophrenic, and surgical patients. The concentration remained almost unaltered after 4 weeks of zuclopenthixol treatment in the schizophrenia group and following various neuroleptic, antidepressant, and anxiolytic medications in the nonschizophrenic patients despite a significant decrease of overt psychopathology assessed by the Brief Psychiatric Rating Scale.

Low levels of somatostatin-like immunoreactivity in neocortex resected from presumed seizure foci in epileptic patients

The concentration of somatostatin-like immunoreactivity (SS-LI) was determined by radioimmunoassay in neocortical tissue resected from 20 patients with pharmacologically intractable complex partial seizures. Most resections included either the anterior temporal pole neocortex (15 cases) or cingulate gyrus neocortex (3 cases). The concentration of SS-LI was lowest in cortical tissue immediately adjacent to cortical tumors. Preoperative electrical recordings suggested that this tissue was the seizure focus. In vitro recordings showed that this tissue also exhibited abnormal hyperexcitable synaptic responses. Higher levels of SS-LI, similar to normal values previously reported in human cortex, were present in non-focal temporal neocortical tissue (resected from patients in whom the seizure focus was in the ipsilateral hippocampus) in which no hyperexcitable synaptic activity was present in vitro. The functional loss of inhibitory transmitters suggested by the low SS-LI levels might provide a theoretical basis for the hyperexcitability observed in vivo and in vitro.

Effect of various neurotransmitters and neuropeptides on the release of corticotropin-releasing hormone from the rat cortex in vitro

Corticotropin-releasing hormone (CRH), in addition to its neuroendocrine role, may act as a central neurotransmitter. Cerebral cortical CRH may have an important role in behavioral and neurodegenerative disorders. To gain an understanding of factors that may influence cortical CRH, we investigated the effect of several neurotransmitters and neuropeptides on the release of immunoreactive CRH (iCRH) from various cerebral cortical regions [frontal (FC), parietal (PC), temporal (TC), and occipital (OC)] in vitro. The hypothalamic release of iCRH was also evaluated under the same experimental conditions. Basal release of iCRH was approximately 2-fold, and KCl-stimulated iCRH release was approximately 4-fold higher in the hypothalamus than in any of the cortical regions. Cortical iCRH release was stimulated by 10 nM somatostatin (SRIF) in PC and 1 nM neuropeptide Y (NPY) in TC. Cortical iCRH release was inhibited by 1 and 10 nM acetylcholine (ACh), 0.1 microM glutamate, and 10 nM NPY. These effects were confined to the FC and/or PC. Hypothalamic iCRH release was stimulated by 1 and 10 nM ACh, 10 microM GABA, and 1 and 10 nM serotonin but was inhibited by 10 nM SRIF and 1 microM GABA. Growth hormone-releasing hormone did not affect cortical or hypothalamic iCRH release. These results demonstrate that CRH release from the cerebral cortex and the hypothalamus are under different regulatory mechanism(s). Furthermore, they indicate that the release of CRH in various cortical regions may be regulated differentially by the same neurotransmitter.

Neurochemical markers in the cerebrospinal fluid of patients with Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis and normal controls

Several neurotransmitter markers were investigated in the cerebrospinal fluid (CSF) from patients with Alzheimer's disease (AD) (n = 27), Parkinson's disease (PD) (n = 35) and ALS (n = 26) and from control subjects (n = 34) to compare the possible alterations in the biochemical profiles of these different neurodegenerative diseases. The main proportion of the patients represented an early phase of the illness at the time of the diagnosis. Correlations of the degree of dementia and the stage of the disease with CSF measures were evaluated. The CSF levels of somatostatin like-immunoreactivity (SLI) were significantly reduced in AD patients when compared with those of normals and ALS patients. The CSF concentrations of homovanillic acid (HVA) were significantly decreased for PD patients and the decrease focused on the non-demented patients. A trend of decreasing HVA values towards the most advanced stage of Parkinson's disease assessed by Webster's scale was also displayed. The content of 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF was higher for ALS patients than for other groups. The lowest 5-hydroxy-indoleacetic acid (5HIAA) levels were observed in the PD group and the lowest acetylcholinesterase (AChE) activities were found in the PD patients with the most severe disease. Changes in CSF measures were too subtle to be beneficial for diagnostic purposes, but adequate for reflecting the different neurochemical profiles of these three degenerative neurological disorders.

Somatostatin in Alzheimer's disease and depression

Somatostatin (somatotropin release-inhibiting factor, SRIF) was originally discovered (1) during the purification of growth hormone-releasing factor from rat hypothalamus and was subsequently isolated and characterized (2) in 1972 from ovine hypothalamus. Since its initial characterization, SRIF has been shown to fulfill criteria for a neurotransmitter and to directly modulate neuronal activity as well as acting as an inhibitory factor regulating endocrine and exocrine secretion. Alterations in cerebrospinal fluid (CSF) concentrations of SRIF have been reported in several diseases exhibiting prominent cognitive dysfunction, including Alzheimer's disease (AD), major depression, Huntington's chorea, multiple sclerosis, schizophrenia and Parkinson's disease, while evidence for regional brain tissue concentration deficits in SRIF are more specific for AD. This mini-review will focus on the studies reporting alterations in CSF and postmortem tissue concentrations of SRIF in AD and depression.

Somatostatin and cognitive functions in Alzheimer's disease--the relationship of cerebrospinal fluid somatostatin increase with clinical response to tetrahydroaminoacridine

We studied the effect of tetrahydroaminoacridine (THA) on cerebrospinal fluid somatostatin-like immunoreactivity (CSF-SLI) in probable Alzheimer disease (AD) patients (n = 20) who took part in an open THA treatment trial. The maintenance dose (100 mg/day) was continued for 4 weeks. Samples of CSF were obtained before treatment and at the end of the treatment period. The CSF-SLI increased significantly (P = 0.01) in the responders for the treatment (increase of the Mini-Mental State Examination score greater than or equal to 3; n = 11), while the non-responders (n = 9) showed a significant decrease of CSF-SLI (P = 0.003). The change of CSF-SLI had also a significant correlation (P = 0.001) with neuropsychological performance. We conclude that the effects of of THA on the CSF-SLI may be due to presynaptic cholinergic or direct somatostatinergic stimulation.

A correlation study of CSF neuropeptides in Alzheimer's and Parkinson's disease

The concentrations of somatostatin (SRIF), vasoactive intestinal polypeptide (VIP), beta-endorphin (beta-EP), adrenocorticotropin (ACTH) and corticotropin-releasing factor (CRF) immunoreactivity were measured in cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD), patients with Parkinson's disease (PD) and controls. In order to study the mechanisms that regulate peptide levels in CSF and peptide interactions, correlations between CSF peptides were determined. Within all patient groups a number of significant correlations were shown to exist between CSF peptides. The correlations were apparently not coincidental, since there was no such relation between the concentrations of CSF peptides and CSF protein content. Neither age, sex, severity of dementia nor the presence of extrapyramidal signs could explain the number of significant correlations. These results indicate, that the correlations found between CSF peptides may be due to common regulatory mechanisms or general physiological behaviour of peptides in the CSF.

Coexistence of muscarinic acetylcholine receptors and somatostatin in nonpyramidal neurons of the rat dorsal hippocampus

This study describes the colocalization of muscarinic acetylcholine receptors (mAChRs) and the neuropeptide somatostatin (SOM) in nonpyramidal neurons of the rat dorsal hippocampus. SOM and mAChRs were identified by immunocytochemistry employing antibody S309 and M35, respectively. Half of the SOMergic cell population is found to be immunoreactive for muscarinic receptor protein as obtained by fluorescent double-labeling techniques. These findings provide additional evidence for a direct cholinergic influence upon SOMergic, nonpyramidal neurons, and defines the anatomical distribution of SOMergic, cholinoceptive neurons in the dorsal hippocampus. Concerning the muscarinic cholinoceptive, nonpyramidal neuron population of the dorsal hippocampus, a considerable number (approximately one-third) was found to be colocalized with somatostatin. These results indicate that a significant part of the cholinergic influence upon hippocampal nonpyramidal neurons is relayed via SOMergic neurons.

Correlations of regional postmortem enzyme activities with premortem local glucose metabolic rates in Alzheimer's disease

Correlations were sought between local cerebral metabolic rates (LCMRs) for glucose in various regions of the cortex, determined in premortem PET scans, with the regional activities of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), beta-glucuronidase (Gluc, a probable index of reactive gliosis), and phosphate-activated glutaminase (PAG, a possible indice of the large pyramidal neurons) measured on postmortem tissue. Significant negative correlations between LCMRs and Gluc activities were found in 6 PET-scanned cases of Alzheimer disease (AD), and positive correlations of LCMRs with PAG were found in 5. By contrast, a positive correlation with ChAT and AChE was found in only 1. The results are consistent with the metabolic deficits in AD being primarily a reflection of local neuronal loss and gliosis. Similar data on two cases of Huntington's disease showed no significant correlations, while 1 patient with Parkinson dementia showed a significant (negative) correlation only with Gluc.

Neurotransmitter changes in Alzheimer's disease: implications to diagnostics and therapy

Changes in the cholinergic, serotonergic, noradrenergic, dopaminergic, GABAergic and somatostatinergic neurons were investigated to determine their roles in Alzheimer's disease (AD). Markers for these systems were analyzed in postmortem brain samples from 20 patients with AD and 14 controls. In the CSF study, markers for the cholinergic neurons (choline esterase, ChE) and for the somatostatinergic neurons (somatostatin-like immunoreactivity, SLI) were assayed for 93 and 75 probable AD patients and 29 and 19 controls, respectively. Activity of choline acetyltransferase (CAT) was decreased by 50-85% in four cortical areas and hippocampus in patients with AD, but not in other areas of the brain, indicating a profound deficit in the function of cholinergic projections ascending from the nucleus basalis to the cerebral cortex and hippocampus in AD. Muscarinic receptor binding was reduced by 18% in the frontal cortex but not in other areas of the brain in AD. Serotonin (5HT) concentrations were reduced (by 21-37%) in hippocampal cortex, hippocampus and striatum; and 5HT metabolite levels were lowered (by 39-54%) in three cortical areas, thalamus and putamen in AD patients. Concentrations of noradrenaline (NA) were reduced (18-36%) in frontal and temporal cortex and putamen. These data imply that serotonergic and noradrenergic projections are also affected in AD but less than the cholinergic neurons. Dopamine (DA) concentrations in AD patients were reduced by 18-27% in temporal and hippocampal cortex and hippocampus, while HVA, the metabolite of DA, was unaltered. Glutamic acid decarboxylase activity was not altered in AD. SLI was decreased (28-42%) in frontal, temporal and parietal cortex, but not in thalamus and putamen in patients with AD. Frontal tangle scores correlated most strongly with cortical CAT activity reduction and less so with decreases of 5HT, NA and DA, indicating a closer correlation with the cholinergic changes and severity of AD than with other neurotransmitter deficiencies. ChE activity and SLI were reduced by 20% and 35%, respectively, in CSF of the whole group of AD patients as compared to the controls. Comparison of CSF findings between four subgroups of dementia severity indicated that the SLI was already reduced in the group of mildest AD (-31%), while ChE activity was not. Although ChE activity in CSF declined in relation to dementia severity, however, the maximal reduction was only modest (-30%). On the other hand, SLI in CSF showed only a slight further reduction (up to -41%) as the dementia become more severe.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatostatin-like immunoreactivity in the CSF of patients with dementia associated with alcoholism

Cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 9 patients with chronic alcohol ingestion and dementia associated with alcoholism and for 8 age-equivalent controls. The CSF SLI was significantly reduced (32%) in the alcoholics with dementia as compared to the controls. This finding is in accordance with previous observations on the relationship between reduced CSF SLI and cognitive impairment in various neuropsychiatric disorders, and extends this finding to patients with dementia associated with alcoholism.

Decreased somatostatin-like immunoreactivity in the cerebrospinal fluid of chronic schizophrenic patients with cognitive impairment

The level of cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 11 chronic schizophrenic patients with moderate cognitive impairment and for 8 controls. The CSF SLI was significantly reduced (37%) in schizophrenic patients, but this decrease did not correlate with the degree of cognitive decline measured by the Mini-Mental State Examination, with psychotic symptoms estimated by the Brief Psychiatric Rating Scale, or with the neuroleptic dose. Although a reducing effect of long-term neuroleptic treatment cannot be totally excluded, the present study suggests that the CSF SLI level is decreased in cognitively impaired schizophrenic patients, as in many other disorders with cognitive impairment.

Neuropeptides and Alzheimer's disease

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

Cerebrospinal fluid somatostatin in delirium. II. Changes at the acute stage and at one year follow-up

Cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for elderly delirious patients during the acute stage and after one-year follow-up. The SLI levels were compared with age-equivalent controls. For the group as a whole, and also when the group was subdivided according to the severity of cognitive decline at the acute stage, type of delirium, or the central nervous system disease, delirious patients showed significant reduction of SLI as compared with the controls. In the follow-up, we observed a further reduction of CSF SLI together with significant correlations in the second and third samples between SLI levels and Mini-Mental State Examination score. Our results suggest a role for somatostatinergic dysfunction in the genesis of some symptoms of delirium. This dysfunction may be a common phenomenon in various forms of delirium and dementia.

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

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

Cerebrospinal fluid monoamine metabolites and neuropeptides in patients with panic disorder

Concentrations of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 3-methoxy-4-hydroxyphenylglycol (MHPG) as well as somatostatin (SRIF) and beta-endorphin (beta-END) were assayed in the cerebrospinal fluid (CSF) of 34 patients with panic disorder and of ten neurological controls. No aberrations of the monoaminergic or peptidergic variables measured were found in the nonpanic state of patients with panic disorder. A modest correlation (P = 0.04) between total anxiety scores and CSF MHPG was observed.

Peptides in the neocortex in Alzheimer's disease and ageing

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

Morris water task impairment and hypoactivity following cysteamine-induced reductions of somatostatin-like immunoreactivity

The effects of cysteamine-induced reductions of somatostatin-like immunoreactivity (SLI) on spatial learning, passive avoidance, and locomotor activity were examined in adult Sprague-Dawley rats. Cysteamine hydrochloride (100 mg/kg, s.c.) produced 54% and 50% reductions in SLI in cortex and hippocampus, respectively, and impaired escape latencies and spatial probe behavior in the Morris water task. Although cysteamine-treated rats displayed hypoactivity in the activity boxes, their swim speed in the Morris water task was unaffected. Cysteamine did not impair passive avoidance retention when administered immediately following training or prior to daily retention testing. These results suggest a role for somatostatin in spatially-mediated behaviors in rats.

Ultrastructural localization of somatostatin-like immunoreactivity in the rat dentate gyrus

Neurons containing somatostatin (SOM) are enriched in the dentate gyrus. We sought to establish the ultrastructural localization of this peptide in the dentate gyrus of the rat brain with a double-bridged peroxidase-antiperoxidase (PAP) method localizing antisera directed against somatostatin (SOM)-28 and SOM-28. Initial light microscopic observations confirmed that the majority of perikarya and thick varicose processes with intense SOM-like immunoreactivity (SOM-LI) were observed in the hilus. Fine varicose processes with SOM-LI were found throughout all layers of the dentate gyrus but were most intense in the outer third of the molecular layer (ML), where an occasional perikaryon with SOM-LI was seen. By electron microscopy, SOM-LI was found in neuronal perikarya, dendrites, axons, and axon terminals. Two types of SOM-containing perikarya were observed. The first type was small (6-10 microns), round or avoid, and had a labeled cytoplasma with abundant Golgi complexes and a dense accumulation of PAP-reaction product. The second type of perikarya was larger (11-16 microns) and had a more abundant cytoplasm than the first type, but the Golgi complexes did not appear labeled. Most (96% of 374) of the synapses on the SOM-labeled perikarya and dendrites were from terminals without SOM-LI which formed nearly equal proportions of asymmetric and symmetric junctions. The remainder of the presynaptic terminals contained SOM-LI and made primarily symmetric synapses. Synaptic junctions from both unlabeled and labeled terminals were primarily on the shafts of the small (0.5-1.5 microns) SOM-immunoreactive dendrites. The terminals with SOM-LI (0.25-1.3 microns) contained many small, clear vesicles and from zero to four large dense-core vesicles. Terminals with SOM-LI were associated 1) with one unlabeled perikaryon or dendrite (49% of 215 in the hilus; 76% of 326 in the ML); 2) with two unlabeled perikarya or dendrites simultaneously (5% hilus; 4% ML); and 3) with one SOM-containing perikaryon or dendrite (6% hilus; 3% ML). In all three types of associations, synaptic contacts on perikarya were few while the majority were with small (distal) dendrites. Moreover, most of the terminals with SOM-LI formed symmetric junctions or lacked membrane specializations but were without any apparent glial intervention in the plane of section analyzed. The remaining SOM-labeled terminals (40% hilus; 17% ML) were without any apparent synaptic relations. However, a few of these terminals were in direct apposition to other terminals, some of which were also SOM-immunoreactive.(ABSTRACT TRUNCATED AT 400 WORDS)

Cerebrospinal fluid somatostatin in delirium

Cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 67 elderly patients who met the DSM-III criteria for delirium and for 19 age-matched controls. As a group, and also when subdivided according to the type of delirium, severity of cognitive decline or the type of central nervous system disease, the delirious patients showed significant reductions of SLI compared with the controls, together with a declining trend associated with increasing cognitive dysfunction. These findings are in accordance with previous observations that reduced CSF SLI is associated with diseases in which cognitive function is disturbed and they extend this finding to delirium.

Somatostatin and beta-endorphin levels in cerebrospinal fluid of nonmedicated and medicated patients with epileptic seizures

Neuropeptides have been proposed to play a role in regulation of the seizure threshold and interictal behavior in experimental models of epilepsy, but there are few studies concerning neuropeptides in human epilepsy. We compared the levels of two peptides, somatostatin (SLI) and beta-endorphin (BEP) in lumbar cerebrospinal fluid (CSF) of unmedicated (N = 18) and medicated (n = 24) epileptic patients with the levels of these peptides in control (n = 20). Peptide levels in the CSF of patients with panic disorder (8) were also evaluated. Patients with chronic medicated epilepsy had a SLl level 80% (p = 0.003, Mann-Whitney U-test) that of the controls, 76% (p = 0.011) that of unmedicated patients, and 84% (p = 0.028) that of the panic group. BEP in the CSF did not differ in unmedicated, medicated and control patients. On the other hand, patients with panic disorder had higher levels of BEP in CSF than did the controls (117%, p = 0.041). In panic patients SLl was at control level. The present study indicates that the peptidergic systems are affected differentially in epilepsy and in panic disorder. Furthermore, there seems to be selectivity in the affect on peptidergic systems during the period when the epilepsy becomes chronic.

The time of origin of somatostatin-immunoreactive neurons in the rat hippocampal formation

Experiments utilizing a combination of [3H]thymidine autoradiography and immunohistochemistry were conducted to determine the time of origin of somatostatin-immunoreactive (SSIR) neurons in the hippocampal formation of the rat. A quantitative and topographic description of neurogenesis in this peptide-containing neuronal system was generated using a computer-aided system to plot the position of labeled cells. Dissected and 'flattened' hippocampal preparations were used to facilitate the analysis of spatial gradients of SSIR cell development. The results indicate that most SSIR hippocampal cells are generated during a short embryonic period which extends from the 12th through the 15th day of gestation (E12-E15). Within this period of development, the distribution of SSIR cells follows a spatial gradient along the transverse or subiculo-dentate axis of the hippocampus. The earliest formed SSIR neurons, generated on E12 and E13, are preferentially distributed to the subiculum, those generated on E14 are most commonly observed throughout the CA1-CA3 fields of the hippocampus and SSIR neurons which become postmitotic on E15 are more heavily represented in the hilar region of the dentate gyrus than cells born at other stages of development. There was no clear-cut neurogenic gradient along the septotemporal axis of the hippocampus. These results indicate that somatostatin cells in the rat hippocampal formation are generated during the same prenatal period when glutamic acid decarboxylase (GAD)-positive neurons become postmitotic. These studies also suggest that quantitative developmental analyses of chemically specific cell types can reveal prominent features of cortical ontogeny that are not readily apparent in standard [3H]thymidine preparations.

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.

Cerebrospinal fluid somatostatin correlates with spectral EEG variables and with parietotemporal cognitive dysfunction in Alzheimer patients

Somatostatin levels of the cerebrospinal fluid (CSF) were correlated with variables of quantitative EEG and with neuropsychological performance in patients with probable Alzheimer's disease. Low somatostatin levels of CSF correlated with decreased beta activity and with decreased mean frequency in the combined alpha and theta EEG range. In the subgroup of mild Alzheimer cases CSF somatostatin correlated positively also with alpha power, and the peak and the mean frequency, and negatively with theta power but not with delta activity. Furthermore, low somatostatin of the CSF correlated with neuropsychological tests assessing temporoparietal dysfunction. To our knowledge, this is the first study to indicate the correlation between spectral analysis results of the EEG and CSF somatostatin suggesting that the relationship between somatostatin and EEG variables is worthy of further studies.

Decreased muscarinic receptor binding in cerebral cortex and hippocampus in Alzheimer's disease

Muscarinic (cholinergic) receptor binding sites (MRB) were studied by determining the 3H-QNB binding in four cortical areas and hippocampus of 20 histologically confirmed Alzheimer patients and comparing these with corresponding controls. Alzheimer patients dying at younger age (less than or equal to 80) with profound decrease in choline-acetyltransferase activity (by 61-85%) and without any, possibly MRB modifying, drug treatment showed 30% decrease in MRB in the frontal cortex (p less than 0.05), 28% in the temporal cortex (p less than 0.05) and 37% in the hippocampus (p less than 0.01). These findings further suggest that muscarinic receptors are affected in Alzheimer's disease, at least in advanced state of the disease.