Per-Göran Gillberg

Receptor alterations in manganese intoxicated monkeys

The density of four different receptors and one marker of dopamine uptake sites were analyzed in monkey brains after manganese exposure (0.1 g manganese per month during 26 months, a dose comparable to that workers might inhale in dusty environments) by means of quantitative receptor autoradiography. The binding of3H-mazindol to the dopamine uptake sites was reduced by 75% in both the head of the caudate nucleus and putamen, while it remained unchanged in the other regions analyzed. The binding of the D1 receptor ligand3H-SCH 23 390 was reduced about 45% in the same areas as mazindol binding, while the density of D2 receptors was unaffected. The muscarinic acetylcholine receptors as well as GABAA receptors remained also unchanged in all brain areas analyzed after manganese exposure. Thus the dopaminergic neurons must be considered to be vulnerable to manganese concentrations attainable in the work environment. Our results also indicate that postsynaptic structures containing D1 receptors are sensitive while cells containing D2 receptors are either spared or compensated for by up-regulation of the number of receptors on remaining sites.

Amyloid tracers detect multiple binding sites in Alzheimer’s disease brain tissue

Imaging fibrillar amyloid-β deposition in the human brain in vivo by positron emission tomography has improved our understanding of the time course of amyloid-β pathology in Alzheimers disease. The most widely used amyloid-β imaging tracer so far is (11)C-Pittsburgh compound B, a thioflavin derivative but other (11)C- and (18)F-labelled amyloid-β tracers have been studied in patients with Alzheimers disease and cognitively normal control subjects. However, it has not yet been established whether different amyloid tracers bind to identical sites on amyloid-β fibrils, offering the same ability to detect the regional amyloid-β burden in the brains. In this study, we characterized (3)H-Pittsburgh compound B binding in autopsied brain regions from 23 patients with Alzheimers disease and 20 control subjects (aged 50 to 88 years). The binding properties of the amyloid tracers FDDNP, AV-45, AV-1 and BF-227 were also compared with those of (3)H-Pittsburgh compound B in the frontal cortices of patients with Alzheimers disease. Saturation binding studies revealed the presence of high- and low-affinity (3)H-Pittsburgh compound B binding sites in the frontal cortex (K(d1): 3.5 ± 1.6 nM; K(d2): 133 ± 30 nM) and hippocampus (K(d1):5.6 ± 2.2 nM; K(d2): 181 ± 132 nM) of Alzheimers disease brains. The relative proportion of high-affinity to low-affinity sites was 6:1 in the frontal cortex and 3:1 in the hippocampus. One control showed both high- and low-affinity (3)H-Pittsburgh compound B binding sites (K(d1): 1.6 nM; K(d2): 330 nM) in the cortex while the others only had a low-affinity site (K(d2): 191 ± 70 nM). (3)H-Pittsburgh compound B binding in Alzheimers disease brains was higher in the frontal and parietal cortices than in the caudate nucleus and hippocampus, and negligible in the cerebellum. Competitive binding studies with (3)H-Pittsburgh compound B in the frontal cortices of Alzheimers disease brains revealed high- and low-affinity binding sites for BTA-1 (Ki: 0.2 nM, 70 nM), florbetapir (1.8 nM, 53 nM) and florbetaben (1.0 nM, 65 nM). BF-227 displaced 83% of (3)H-Pittsburgh compound B binding, mainly at a low-affinity site (311 nM), whereas FDDNP only partly displaced (40%). We propose a multiple binding site model for the amyloid tracers (binding sites 1, 2 and 3), where AV-45 (florbetapir), AV-1 (florbetaben), and Pittsburgh compound B, all show nanomolar affinity for the high-affinity site (binding site 1), as visualized by positron emission tomography. BF-227 shows mainly binding to site 3 and FDDNP shows only some binding to site 2. Different amyloid tracers may provide new insight into the pathophysiological mechanisms in the progression of Alzheimers disease.

Muscarinic binding sites in small homogenates and in autoradiographic sections from rat and human spinal cord

Binding of labelled L- quinuclidinylbenzylate was studied in cryosections and homogenates of human and rat spinal cord. For the cryosections an autoradiographic method was used. With both techniques a higher density of muscarinic binding sites was found in rat than in human spinal cord. In the autoradiographs very high densities of muscarinic binding sites were observed in the motor neurone area and in the apical part of the dorsal horn. The latter high density region was not always found in homogenates from dissected tissue samples. The autoradiographic technique has a better resolution for detecting discrete regional variations in the receptor content of the spinal cord.

3H-Deprenyl and 3H-PIB autoradiography show different laminar distributions of astroglia and fibrillar β-amyloid in Alzheimer brain

BackgroundThe pathological features in Alzheimer’s disease (AD) brain include the accumulation and deposition of β-amyloid (Aβ), activation of astrocytes and microglia and disruption of cholinergic neurotransmission. Since the topographical characteristics of these different pathological processes in AD brain and how these relate to each other is not clear, this motivated further exploration using binding studies in postmortem brain with molecular imaging tracers. This information could aid the development of specific biomarkers to accurately chart disease progression.ResultsIn vitro binding assays demonstrated increased [3H]-PIB (fibrillar Aβ) and [3H]-PK11195 (activated microglia) binding in the frontal cortex (FC) and hippocampus (HIP), as well as increased binding of [3H]-l-deprenyl (activated astrocytes) in the HIP, but a decreased [3H]-nicotine (α4β2 nicotinic acetylcholine receptor (nAChR)) binding in the FC of AD cases compared to age-matched controls. Quantitative autoradiography binding studies were also performed to investigate the regional laminar distributions of [3H]-l-deprenyl, [3H]-PIB as well as [125I]-α-bungarotoxin (α7 nAChRs) and [3H]-nicotine in hemisphere brain of a typical AD case. A clear lamination pattern was observed with high [3H]-PIB binding in all layers and [3H]-deprenyl in superficial layers of the FC. In contrast, [3H]-PIB showed low binding to fibrillar Aβ, but [3H]-deprenyl high binding to activated astrocytes throughout the HIP. The [3H]-PIB binding was also low and the [3H]-deprenyl binding high in all layers of the medial temporal gyrus and insular cortex in comparison to the frontal cortex. Low [3H]-nicotine binding was observed in all layers of the frontal cortex in comparison to layers in the medial temporal gyrus, insular cortex and hippocampus. Immunohistochemical detection in the AD case revealed abundant glial fibrillary acidic protein positive (GFAP+) reactive astrocytes and α7 nAChR expressing GFAP+ astrocytes both in the vicinity and surrounding Aβ neuritic plaques in the FC and HIP. Although fewer Aβ plaques were observed in the HIP, some hippocampal GFAP+ astrocytes contained Aβ-positive (6 F/3D) granules within their somata.ConclusionsAstrocytosis shows a distinct regional pattern in AD brain compared to fibrillar Aβ, suggesting that different types of astrocytes may be associated with the pathophysiological processes in AD.

Chapter 37 Spinal cholinergic mechanisms

Publisher Summary This chapter provides an overview of spinal cholinergic mechanisms. The presence and synthesis of acetylcholine (ACh) in the spinal cord is studied in animal experiments described in the chapter and the first applications of acetylcholinesterase (AChE) histochemistry depicted intense staining of the motor neurons. The highest activity of choline acetyltransferase (ChAT) is found in the ventrolateral part of the ventral horn, which corresponds closely to the distribution pattern of AChE. The main part of this high ChAT activity is located in the motor neurons, as it can be traced into the human ventral root region. In immunohistochemical studies using monoclonal antibody to ChAT, staining is found in the ventral horn of large motor neurons. In addition, large ChAT immunoreactive boutons are observed on the soma and proximal dendrites of large and medium sized somatic motor neurons. Small ChAT-positive neurons are observed throughout the spinal cord. These cells, which are more numerous in the upper lumbar than in the thoracic level of the cord, are grouped together in the central grey matter encircling the central canal within lamina X.

Autoradiographic visualization of extrajunctional acetylcholine receptors in whole human biceps brachii muscle Changes in amyotrophic lateral sclerosis

ABSTRACT – The morphological distribution of acetylcholine receptors in the whole biceps brachii muscle from a patient with amyotrophic lateral sclerosis (ALS) and from a control patient was studied by in vitro autoradiography with 3H‐alpha‐bungarotoxin (alpha‐Btx). In ALS, 3H‐alpha‐Btx binding occurred over the entire muscle, while in the control case the binding was restricted to the motor end‐plate region.

No Re-Expression of High-Affinity Nerve Growth Factor Binding Sites in Spinal Motor Neurons in Amyotrophic Lateral Sclerosis

Autoradiographic studies of high-affinity nerve growth factor binding sites in the cervical human spinal cord revealed a high density of binding sites in the dorsal horn and in the tract of Lissauer, which is in agreement with investigations in nonprimates. Very low or no binding was found in the motor neuron areas of controls as well as in amyotrophic lateral sclerosis cases, which indicates that the degeneration of motor neurons in this disease is not accompanied by re-expression of high-affinity nerve growth factor receptors.

Cortical laminar tau deposits and activated astrocytes in Alzheimer’s disease visualised by 3 H-THK5117 and 3 H-deprenyl autoradiography

Hyperphosphorylated tau protein deposits and, inflammatory processes are characteristic components of Alzheimer disease (AD) pathology. We here aimed to visualize in vitro the distribution of tau deposits and activated astrocytes across the cortical layers in autopsy AD brain tissue using the radiotracers 3H-THK5117 and 3H-deprenyl. 3H-THK5117 and 3H-deprenyl autoradiographies were carried out on frozen brain sections from three AD patients and one healthy control. 3H-THK5117 showed a distinct laminar cortical binding similar to 3H-deprenyl autoradiography, with an extensive binding in the superficial and deep layers of the temporal neocortices, whereas the middle frontal gyrus showed an even binding throughout the layers. Globally, eventhough some differences could be observed, AT8 (tau) and GFAP (astrocyte) immunostaining showed a laminar pattern comparable to their corresponding radiotracers within each AD case. Some variability was observed between the AD cases reflecting differences in disease phenotype. The similar laminar cortical brain distribution of tau deposits and activated astrocytes supports the hypothesis of a close pathological interconnection. The difference in regional binding patterns of 3H-THK5117 and AT8 antibody staining suggest additional tau binding sites detectable by 3H-THK5117.

Neuropharmacology of amyotrophic lateral sclerosis.

Publisher Summary This chapter describes the neuropharmacology of amyotrophic lateral sclerosis (ALS) as expressed on transmitter-related enzymes and receptors in the central nervous system (CNS) and skeletal muscle, with emphasis on cholinergic mechanisms. ALS and other degenerative disorders, such as Parkinsons disease and dementia of the Alzheimer type, are neuropathologically characterized by preferential vulnerability of some neuronal systems and relative resistance of other neuronal systems. Irrespective of the aetiology, the progressive neuronal degenerations should be accompanied by transmitter dysfunction at the synapses of the fiber tracts involved. Insight into such mechanisms might lead to the development of symptomatic pharmacological therapy. In ALS, the degenerative changes are restricted to the cortical spinal tracts and to the lower motor neurons in the brainstem and spinal cord, although the involvement of nonmotor pathways is increasingly recognized. The chapter also focuses on some closely allied therapeutic trials and the search for neurotrophic disturbances and neurotoxic factors in ALS. The different hypotheses concerning the aetiology of ALS are reflected by the large number of treatment strategies, which are discussed in the chapter.

COMPARISON OF BINDING PROPERTIES OF THK5117, THK5351, PBB3 AND T807 IN AUTOPSIES OF ALZHEIMER DISEASE CASES

of interest between AD, CBD, and PSP (Table 2). However, pairwise comparisons using Tukey and Kramer test revealed a significant difference (p1⁄4 0.02) in the proportion of total neurons with ht-NCI between AD and CBD, with AD showing the lower proportion (Figure 1-2). We also detected a significant difference (p1⁄4 0.0023) in the proportion of orexin positive neurons with ht-NCI between AD and CBD, with AD showing the lower proportion (Figure 3-4). Conclusions:Our unbiased stereological investigation detected moderate to high accumulation of phospho-tau in PFN in all three tauopathies. Tau burden in orexinergic neurons show a clear distinction between AD and CBD. Quantitative characterization of tau pathology and neuronal loss in sleep-related nuclei may inform on neurobiological basis of sleep disturbances. Further studies should focus on the role of degeneration of orexinergic neurons in exacerbating sleep fragmentation in AD patients.