The DaNeX study of embryonic mesencephalic, dopaminergic tissue grafted to a minipig model of Parkinson's disease: preliminary findings of effect of MPTP poisoning on striatal dopaminergic markers

A Pig Model to Assess Skin Lesions after Apomorphine Application

Owing to their similarities, pigs are often used as experimental models for humans. In particular, the similarity of the skin allows them to be a good dermatological model. The aim of the study was to develop an animal model in conventional domestic pigs to evaluate skin lesions macroscopically and histologically after a continuous subcutaneous apomorphine application. A total of 16 pigs from two different age groups were injected with four different apomorphine formulations for 12 h daily over a period of 28 days into the subcutis, which was then evaluated macroscopically for nodules and erythema, as well as histologically. Differences in skin lesions between the formulations were found, with formulation 1 leading to the fewest nodules, least skin lesions, no lymph follicles, least necrosis, and best skin tolerance. Older pigs were easier to handle and, because of the thicker skin and subcutis of these animals, drug application with the appropriate needle length was safer. The experimental setup worked well and an animal model to assess skin lesions after a continuous subcutaneous application of drugs could be successfully established.

Selecting the Best Animal Model of Parkinson's Disease for Your Research Purpose: Insight from in vivo PET Imaging Studies

Parkinson's disease (PD) is a debilitating neurodegenerative multisystem disorder leading to motor and non-motor symptoms in millions of individuals. Despite intense research, there is still no cure, and early disease biomarkers are lacking. Animal models of PD have been inspired by basic elements of its pathogenesis, such as dopamine dysfunction, alpha-synuclein accumulation, neuroinflammation and disruption of protein degradation, and these have been crucial for a deeper understanding of the mechanisms of pathology, the identification of biomarkers, and evaluation of novel therapies. Imaging biomarkers are non-invasive tools to assess disease progression and response to therapies; their discovery and validation have been an active field of translational research. Here, we highlight different considerations of animal models of PD that can be applied to future research, in terms of their suitability to answer different research questions. We provide the reader with important considerations of the best choice of model to use based on the disease features of each model, including issues related to different species. In addition, positron emission tomography studies conducted in PD animal models in the last 5 years are presented. With a variety of different species, interventions and genetic information, the choice of the most appropriate model to answer research questions can be daunting, especially since no single model recapitulates all aspects of this complex disorder. Appropriate animal models in conjunction with in vivo molecular imaging tools, if selected properly, can be a powerful combination for the assessment of novel therapies and developing tools for early diagnosis.

Modeling Parkinson's Disease: Not Only Rodents?

Parkinson’s disease (PD) is a common chronic progressive multifactorial neurodegenerative disease. In most cases, PD develops as a sporadic idiopathic disease. However, in 10%–15% of all patients, Mendelian inheritance of the disease is observed in an autosomal dominant or autosomal recessive manner. To date, mutations in seven genes have been convincingly confirmed as causative in typical familial forms of PD, i.e., SNCA, LRRK2, VPS35, PRKN, PINK1, GBA, and DJ-1. Family and genome-wide association studies have also identified a number of candidate disease genes and a common genetic variability at 90 loci has been linked to risk for PD. The analysis of the biological function of both proven and candidate genes made it possible to conclude that mitochondrial dysfunction, lysosomal dysfunction, impaired exosomal transport, and immunological processes can play important roles in the development of the pathological process of PD. The mechanisms of initiation of the pathological process and its earliest stages remain unclear. The study of the early stages of the disease (before the first motor symptoms appear) is extremely complicated by the long preclinical period. In addition, at present, the possibility of performing complex biochemical and molecular biological studies familial forms of PD is limited. However, in this case, the analysis of the state of the central nervous system can only be assessed by indirect signs, such as the level of metabolites in the cerebrospinal fluid, peripheral blood, and other biological fluids. One of the potential solutions to this problem is the analysis of disease models, in which it is possible to conduct a detailed in-depth study of all aspects of the pathological process, starting from its earliest stages. Many modeling options are available currently. An analysis of studies published in the 2000s suggests that toxic models in rodents are used in the vast majority of cases. However, interesting and important data for understanding the pathogenesis of PD can be obtained from other in vivo models. Within the framework of this review, we will consider various models of PD that were created using various living organisms, from unicellular yeast (Saccharomyces cerevisiae) and invertebrate (Nematode and Drosophila) forms to various mammalian species.

From the Gut to the Brain and Back: Therapeutic Approaches for the Treatment of Network Dysfunction in Parkinson's Disease

Parkinson's disease (PD) is a complex, multisystem, progressive, degenerative disorder characterized by severe, debilitating motor dysfunction, cognitive impairments, and mood disorders. Although preclinical research has traditionally focused on the motor deficits resulting from the loss of nigrostriatal dopaminergic neurons, up to two thirds of PD patients present separate and distinct behavioral changes. Loss of basal forebrain cholinergic neurons occurs as early as the loss of dopaminergic cells and contributes to the cognitive decline in PD. In addition, attentional deficits can limit posture control and movement efficacy caused by dopaminergic cell loss. Complicating the picture further is intracellular α-synuclein accumulation beginning in the enteric nervous system and diffusing to the substantia nigra through the dorsal motor neurons of the vagus nerve. It seems that α-synuclein's role is that of mediating dopamine synthesis, storage, and release, and its function has not been completely understood. Treating a complex, multistage network disorder, such as PD, likely requires a multipronged approach. Here, we describe a few approaches that could be used alone or perhaps in combination to achieve a greater mosaic of behavioral benefit. These include (1) using encapsulated, genetically modified cells as delivery vehicles for administering neuroprotective trophic factors, such as GDNF, in a direct and sustained means to the brain; (2) immunotherapeutic interventions, such as vaccination or the use of monoclonal antibodies against aggregated, pathological α-synuclein; (3) the continuous infusion of levodopa-carbidopa through an intestinal gel pad to attenuate the loss of dopaminergic function and manage the motor and non-motor complications in PD patients; and (4) specific rehabilitation treatment programs for drug-refractory motor complications.

PCL/gelatin scaffolds and beta-boswellic acid synergistically increase the efficiency of CGR8 stem cells differentiation into dopaminergic neuron: A new paradigm of Parkinson's disease cell therapy

Parkinson's disease is a progressive degenerative disorder in the central nervous system, which is distinguished by the death of dopamine-producing nerve cells. Levodopa, a dopamine precursor drug, is the current standard of care of symptomatic treatment for Parkinson's disease. However, the long-term use of the drug is associated with the development of motor fluctuations and dyskinesias. Cellular therapies aim to deploy fetal dopaminergic neurons as a means to replace the missing dopamine-producing cells. The present study aims to study the impact of beta-boswellic acid (BBA) coupled with poly ε-caprolactone (PCL)/gelatin scaffolds on the dopaminergic differentiation course of CGR8 embryonic stem cells (ESCs). For this purpose, CGR8 ESCs were cultured on PCL/gelatin scaffolds and a five-step protocol was employed to be promoted the neural differentiation of CGR8 ESCs. Gene expression analysis by real-time qPCR demonstrated that PCL/gelatin scaffolds along with BBA treatment impose synergistic effects on the derivation of dopaminergic-like cells from CGR8 ESCs. Reverse-phase high-performance liquid chromatography confirmed the functionality of the derived neurons by demonstrating the efficient secretion of dopamine in response to stimuli. Our results suggested that the generation of functional dopaminergic-like cells from CGR8 ESCs was increased and supported by PCL/gelatin scaffolds and BBA treatment can heighten the efficiency. The result of this study may open insight into Parkinson's disease cell therapy and provide future directions for tissue engineering aimed at the treatment of Parkinson's disease.

A pilot study on assessment of locomotor behavior using a video tracking system in minipigs

Pigs are often selected for large animal models including for neuroscience and behavioral research, because their anatomy and biochemistry are similar to those of humans. However, behavioral assessments, in combination with objective long-term monitoring, is difficult. In this study, we introduced an automated video tracking system which was previously used in rodent studies, for use with pig models. Locomotor behaviors (total distance, number of zone transitions, and velocity) were evaluated and their changes were validated by different 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration methods and dosing regimens. Three minipigs (23-29 kg) received subcutaneous or intravenous MPTP, either 1 or 3 times per week. Immediately after MPTP injection, the minipigs remained in a corner and exhibited reduced trajectory. In addition, the total distance travelled, number of zone transitions, and velocity were greatly reduced at every MPTP administration in all the minipigs, accompanying to increased resting time. However, the MPTP-induced symptoms were reversed when MPTP administration was terminated. In conclusion, this automated video-tracking system was able to monitor long-term locomotor activity and differentiate detailed alterations in large animals. It has the advantages of being easy to use, higher resolution, less effort, and more delicate tracking. Additionally, as our method can be applied to the animals' home pen, no habituation is needed.

Development and Genome Sequencing of a Laboratory-Inbred Miniature Pig Facilitates Study of Human Diabetic Disease

Pig has been proved to be a valuable large animal model used for research on diabetic disease. However, their translational value is limited given their distinct anatomy and physiology. For the last 30 years, we have been developing a laboratory Asian miniature pig inbred line (Bama miniature pig [BM]) from the primitive Bama xiang pig via long-term selective inbreeding. Here, we assembled a BM reference genome at full chromosome-scale resolution with a total length of 2.49 Gb. Comparative and evolutionary genomic analyses identified numerous variations between the BM and commercial pig (Duroc), particularly those in the genetic loci associated with the features advantageous to diabetes studies. Resequencing analyses revealed many differentiated gene loci associated with inbreeding and other selective forces. These together with transcriptome analyses of diabetic pig models provide a comprehensive genetic basis for resistance to diabetogenic environment, especially related to energy metabolism.

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Bama miniature pig (BM) is one of the pig lines with the highest inbreeding coefficient

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This atlas is a report on the chromosome-level genome assembly of miniature pig

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Genomic analyses revealed genetic basis underlying BM's advantages to study diabetes

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Some lncRNAs and mRNAs may be linked to resistance to diabetogenic environment

Pirouetting pigs: A large non-primate animal model based on unilateral 6-hydroxydopamine lesioning of the nigrostriatal pathway

INTRODUCTION

The rotating 6-hydroxydopamine (6-OHDA) rat model has long been important when developing new treatment strategies for Parkinson's disease (PD). Similar non-human primate models have been developed for translational research purposes as large animal models are required by regulatory bodies as an intermediate "phase 0" trial step. However, experimental research in non-human primates encounters several economical and regulatory issues, which may be avoided by the alternative use of pigs as a large animal model for experimental brain research.

OBJECTIVE

The primary aim of this study was to examine if unilateral injections of 6-OHDA into the Göttingen minipig nigrostriatal pathway would lead to dopaminergic imbalance and rotational behavior similar to the 6-OHDA unilateral symptomatic model of PD created in other species. The secondary aim was to attempt to verify the rotational behavior as a parkinsonian symptom using subthalamic deep brain stimulation (STN-DBS) to minimize the elicited rotational pattern.

MATERIALS AND METHODS

Using an MRI-based stereotactic procedure, ten female Göttingen minipigs were injected unilaterally with 6-OHDA in the nigrostriatal pathway. Postoperatively, an MRI was performed, and the animals were injected with amphetamine and apomorphine and observed for rotational behavior. After a survival period of three months the brains were removed and immunohistochemically stained for tyrosine hydroxylase (TH). One week before sacrifice two animals had DBS electrodes unilaterally implanted in the subthalamic nucleus and various stimulation protocols were conducted during amphetamine challenge.

RESULTS

As expected most animals rotated towards the side of the lesion when given amphetamine (3.5-4.0 mg/kg), whereas the predicted opposite response to apomorphine were much harder to reproduce. T1- and T2-weighted postoperative MRI could demonstrate the size and the location of the 6-OHDA injection. Postmortem TH-staining of the final two animals receiving a medial and a lateral injection of 25 μL of 6-OHDA (8 μg/μL, injection rate 5 μL/min) into the diencephalic nigrostriatal pathway showed a prominent unilateral decrease in TH-staining of the substantia nigra pars compacta, the ventral tegmental area and the nigrostriatal pathway on the lesioned side. These two animals displayed spontaneous rotational behavior toward the lesioned side for the first 2-3 days postoperatively, and this behavior could later on be reelicited by amphetamine and attenuated by ipsilateral STN-DBS.

CONCLUSION

Female Göttingen minipigs are susceptible to unilateral dopaminergic degeneration when properly injected unilaterally with sufficient amounts of 6-OHDA in the nigrostriatal pathway. The location of the 6-OHDA injections and thus the accuracy of the employed stereotaxy can be verified in vivo using MRI postoperatively. The injected minipigs display unilateral parkinsonism with a well-defined rotational response to amphetamine that may be ameliated by STN-DBS performed on the lesioned side. The response to apomorphine was, however, not consistent, illustrating that further work on this promising non-primate large animal model is needed, before it is fully similar to the established 6-OHDA models in other species.

Quantitative [18F]Fluorodopa/PET and Histology of Fetal Mesencephalic Dopaminergic Grafts to the Striatum of MPTP-Poisoned Minipigs

The functional restoration of the dopamine innervation of striatum in MPTP-poisoned Göttingen minipigs was assessed for 6 months following grafting of fetal pig mesencephalic neurons. Pigs were assigned to a normal control group and a MPTP-poisoned group, members of which received no further treatment, or which received bilateral grafts to the striatum of tissue blocks harvested from E28 fetal pig mesencephalon with and without immunosuppressive treatment after grafting, or with additional co-grafting with immortalized rat neural cells transfected to produce GDNF. In the baseline condition, and again at 3 and 6 months postsurgery, all animals were subjected to quantitative [18F]fluorodopa PET scans and testing for motor impairment. At the end of 6 months, tyrosine hydroxylase (TH)-containing neurons were counted in the grafts by stereological methods. The MPTP poisoning persistently reduced the magnitude of k3D, the relative activity of DOPA decarboxylase in striatum, by 60%. Grafting restored the rate of [18F]fluorodopa decarboxylation to the normal range, and normalized the scores in motor function. The biochemical and functional recovery was associated with survival of approximately 100,000 TH-positive graft neurons in each hemisphere. Immunosuppression did not impart a greater recovery of [18F]fluorodopa uptake, nor were the number of TH-positive graft neurons or the volumes of the grafts increased in the immunosuppressed group. Contrary to expectation, co-grafting of transfected GDNF-expressing HiB5 cells, a rat-derived neural cell line, tended to impair the survival of the grafts with the lowest values for graft volumes, TH-positive cell numbers, behavioral scores, and relative DOPA decarboxylase activity. From the results we conclude that pig ventral mesencephalic allografts can restore functional dopamine innervation in adult MPTP-lesioned minipigs.

Exposure of the Pig CNS for Histological Analysis: A Manual for Decapitation, Skull Opening, and Brain Removal

Pigs have become increasingly popular in large-animal translational neuroscience research as an economically and ethically feasible substitute to non-human primates. The large brain size of the pig allows the use of conventional clinical brain imagers and the direct use and testing of neurosurgical procedures and equipment from the human clinic. Further macroscopic and histological analysis, however, requires postmortem exposure of the pig central nervous system (CNS) and subsequent brain removal. This is not an easy task, as the pig CNS is encapsulated by a thick, bony skull and spinal column. The goal of this paper and instructional video is to describe how to expose and remove the postmortem pig brain and the pituitary gland in an intact state, suitable for subsequent macroscopic and histological analysis.

The telencephalon of the Göttingen minipig, cytoarchitecture and cortical surface anatomy

During the last 20 years pigs have become increasingly popular in large animal translational neuroscience research as an economical and ethical feasible substitute to non-human primates. The anatomy of the pig telencephalon is, however, not well known. We present, accordingly, a detailed description of the surface anatomy and cytoarchitecture of the Göttingen minipig telencephalon based on macrophotos and consecutive high-power microphotographs of 15 μm thick paraffin embedded Nissl-stained coronal sections. In 1-year-old specimens the formalin perfused brain measures approximately 55 × 47 × 36 mm (length, width, height) and weighs around 69 g. The telencephalic part of the Göttingen minipig cerebrum covers a large surface area, which can be divided into a neocortical gyrencephalic part located dorsal to the rhinal fissure, and a ventral subrhinal part dominated by olfactory, amygdaloid, septal, and hippocampal structures. This part of the telencephalon is named the subrhinal lobe, and based on cytoarchitectural and sulcal anatomy, can be discerned from the remaining dorsally located neocortical perirhinal/insular, pericallosal, frontal, parietal, temporal, and occipital lobes. The inner subcortical structure of the minipig telencephalon is dominated by a prominent ventricular system and large basal ganglia, wherein the putamen and the caudate nucleus posterior and dorsally are separated into two entities by the internal capsule, whereas both structures ventrally fuse into a large accumbens nucleus. The presented anatomical data is accompanied by surface renderings and high-power macrophotographs illustrating the telencephalic sulcal pattern, and the localization of the identified lobes and cytoarchitectonic areas. Additionally, 24 representative Nissl-stained telencephalic coronal sections are presented as supplementary material in atlas form on http://www.cense.dk/minipig_atlas/index.html and referred to as S1-S24 throughout the manuscript.

Animal behavioral assessments in current research of Parkinson's disease

Parkinson's disease (PD), a neurodegenerative disorder, is traditionally classified as a movement disorder. Patients typically suffer from many motor dysfunctions. Presently, clinicians and scientists recognize that many non-motor symptoms are associated with PD. There is an increasing interest in both motor and non-motor symptoms in clinical studies on PD patients and laboratory research on animal models that imitate the pathophysiologic features and symptoms of PD patients. Therefore, appropriate behavioral assessments are extremely crucial for correctly understanding the mechanisms of PD and accurately evaluating the efficacy and safety of novel therapies. This article systematically reviews the behavioral assessments, for both motor and non-motor symptoms, in various animal models involved in current PD research. We addressed the strengths and weaknesses of these behavioral tests and their appropriate applications. Moreover, we discussed potential mechanisms behind these behavioral tests and cautioned readers against potential experimental bias. Since most of the behavioral assessments currently used for non-motor symptoms are not particularly designed for animals with PD, it is of the utmost importance to greatly improve experimental design and evaluation in PD research with animal models. Indeed, it is essential to develop specific assessments for non-motor symptoms in PD animals based on their characteristics. We concluded with a prospective view for behavioral assessments with real-time assessment with mobile internet and wearable device in future PD research.

Toward sophisticated basal ganglia neuromodulation: Review on basal ganglia deep brain stimulation

This review presents state-of-the-art knowledge about the roles of the basal ganglia (BG) in action-selection, cognition, and motivation, and how this knowledge has been used to improve deep brain stimulation (DBS) treatment of neurological and psychiatric disorders. Such pathological conditions include Parkinson's disease, Huntington's disease, Tourette syndrome, depression, and obsessive-compulsive disorder. The first section presents evidence supporting current hypotheses of how the cortico-BG circuitry works to select motor and emotional actions, and how defects in this circuitry can cause symptoms of the BG diseases. Emphasis is given to the role of striatal dopamine on motor performance, motivated behaviors and learning of procedural memories. Next, the use of cutting-edge electrochemical techniques in animal and human studies of BG functioning under normal and disease conditions is discussed. Finally, functional neuroimaging studies are reviewed; these works have shown the relationship between cortico-BG structures activated during DBS and improvement of disease symptoms.

Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders

Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.

Magnetic resonance imaging evaluation of Yukatan minipig brains for neurotherapy applications

Magnetic resonance imaging (MRI) of six Yukatan minipig brains was performed. The animals were placed in stereotaxic conditions currently used in experiments. To allow for correctpositioning of the animal in the MRI instrument, landmarks were previously traced on the snout of the pig. To avoid movements, animal were anesthetized. The animals were placed in a prone position in a Siemens Magnetom Avanto 1.5 System with a head coil. Axial T2-weighted and sagittal T1-weighted MRI images were obtained from each pig. Afterwards, the brains of the pigs were fixed and cut into axial sections. Histologic and MR images were compared. The usefulness of this technique is discussed.

MRI-guided stereotaxic targeting in pigs based on a stereotaxic localizer box fitted with an isocentric frame and use of SurgiPlan computer-planning software

We present a stereotaxic procedure enabling MRI-guided isocentric stereotaxy in pigs. The procedure is based on the Leksell stereotaxic arch principle, and a stereotaxic localizer box with an incorporated fiducial marking system (sideplates) defining a stereotaxic space similar to the clinical Leksell system. The obtained MRIs can be imported for 3D-reconstruction and coordinate calculation in the clinical stereotaxic software planning system (Leksell SurgiPlan, Elekta AB, Sweden). After MRI the sideplates are replaced by a modified Leksell arch accommodating clinical standard manipulators for isocentric placement of DBS-electrodes, neural tracers and therapeutics in the calculated target coordinates. The mechanical accuracy of the device was within 0.3-0.5 mm. Stereotaxic MRIs were imported to the stereotaxic software planning system with a mean error of 0.4-0.5 mm and a max error of 0.8-0.9 mm. Application accuracy measured on a phantom and on inserted skull markers in nine pigs was within 1 mm in all planes. The intracerebral application accuracy found after placement of 10 manganese trajectories within the full extent of the intracerebral stereotaxic space in two minipigs was equally randomly distributed and within 0.7+/-0.4; 0.5+/-0.4; and 0.7+/-0.3mm in the X, Y, and Z plane. Injection of neural tracers in the subgenual gyrus of three minipigs and placement of encapsulated gene-modified cells in four minipigs confirmed the accuracy and functionality of the described procedure. We conclude that the devised technique and instrumentation enable high-precision stereotaxic procedures in pigs that may benefit future large animal neuroscience research and outline the technical considerations for a similar stereotaxic methodology in other animals.

Animal Models of Neurodegenerative Disease: Insights from In vivo Imaging Studies

Animal models have been used extensively to understand the etiology and pathophysiology of human neurodegenerative diseases, and are an essential component in the development of therapeutic interventions for these disorders. In recent years, technical advances in imaging modalities such as positron emission tomography (PET) and magnetic resonance imaging (MRI) have allowed the use of these techniques for the evaluation of functional, neurochemical, and anatomical changes in the brains of animals. Combining animal models of neurodegenerative disorders with neuroimaging provides a powerful tool to follow the disease process, to examine compensatory mechanisms, and to investigate the effects of potential treatments preclinically to derive knowledge that will ultimately inform our clinical decisions. This article reviews the literature on the use of PET and MRI in animal models of Parkinson's disease, Huntington's disease, and Alzheimer's disease, and evaluates the strengths and limitations of brain imaging in animal models of neurodegenerative diseases.

A PET study of effects of chronic 3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”) on serotonin markers in Göttingen minipig brain

The psychostimulant 3,4-methylendioxymethamphetamine (MDMA, "ecstasy") evokes degeneration of telencephalic serotonin innervations in rodents, nonhuman primates, and human recreational drug users. However, there has been no alternative to nonhuman primates for studies of the cognitive and neurochemical consequences of serotonin depletion in a large-bodied animal. Therefore, we used positron emission tomography (PET) with [(11)C]DASB to map the distribution of plasma membrane serotonin transporters in brain of Göttingen minipigs, first in a baseline condition, and again at 2 weeks after treatment with MDMA (i.m.), administered at a range of doses. In parallel PET studies, [(11)C]WAY-100635 was used to map the distribution of serotonin 5HT(1A) receptors. The acute MDMA treatment in awake pigs evoked 1 degrees C of hyperthermia. MDMA at total doses greater than 20 mg/kg administered over 2-4 days reduced the binding potential (pB) of [(11)C]DASB for serotonin transporters in porcine brain. A mean total dose of 42 mg/kg MDMA in four animals evoked a mean 32% decrease in [(11)C]DASB pB in mesencephalon and diencephalon, and a mean 53% decrease in telencephalic structures. However, this depletion of serotonin innervations was not associated with consistent alterations in the binding of [(11)C]WAY-100635 to serotonin 5HT(1A) receptors. Stereological cell counting of serotonin-positive neurons, which numbered 95,000 in the dorsal raphé nucleus of normal animals, was unaffected in MDMA-treated group. group.

The use of pigs in neuroscience: Modeling brain disorders

The use of pigs in neuroscience research has increased in the past decade, which has seen broader recognition of the potential of pigs as an animal for experimental modeling of human brain disorders. The volume of available background data concerning pig brain anatomy and neurochemistry has increased considerably in recent years. The pig brain, which is gyrencephalic, resembles the human brain more in anatomy, growth and development than do the brains of commonly used small laboratory animals. The size of the pig brain permits the identification of cortical and subcortical structures by imaging techniques. Furthermore, the pig is an increasingly popular laboratory animal for transgenic manipulations of neural genes. The present paper focuses on evaluating the potential for modeling symptoms, phenomena or constructs of human brain diseases in pigs, the neuropsychiatric disorders in particular. Important practical and ethical aspects of the use of pigs as an experimental animal as pertaining to relevant in vivo experimental brain techniques are reviewed. Finally, current knowledge of aspects of behavioral processes including learning and memory are reviewed so as to complete the summary of the status of pigs as a species suitable for experimental models of diverse human brain disorders.

Development of DARPP-32-positive parts of fetal pig ganglionic eminence and ventral mesencephalon in organotypic slice co-cultures

Neurons from the fetal pig dopaminergic ventral mesencephalon (VM) and basal ganglia anlage (the ganglionic eminence) were co-cultured as organotypic slice cultures to study the development of the two interconnected brain areas. During a short developmental period (E35-E42), a groove separates the ganglionic eminence into a lateral and a medial part. This was used (a) to study the developmental expression of the striatal marker protein, dopamine and adenosine 3,5-monophosphate regulated phospho-protein (DARPP-32) in the two parts and (b) to compare innervations of the two parts by tyrosine hydroxylase (TH)-positive, dopaminergic fibers from co-cultured slices of the ventral mesencephalon. DARPP-32 expression was more extensive and dense in cultures of the lateral part of the striatal anlage than the medial part. The DARPP-32-positive areas moreover overlapped with areas rich in acetylcholine esterase (AChE) and were the preferred target areas for TH-positive fibers from the co-cultured VM.

Distribution of PK11195 binding sites in porcine brain studied by autoradiography in vitro and by positron emission tomography

The cerebral distribution of peripheral-type benzodiazepine binding sites (PBBS) in human brain has been investigated by positron emission tomography (PET) with the specific radioligand [11C]PK11195 in diverse neuropathological conditions. However, little is known about the pattern of PK11195 binding sites in healthy brain. Therefore, we used quantitative autoradiography to measure the saturation binding parameters for [3H]PK11195 in cryostat sections from young Landrace pigs. Specific binding was lowest in the cerebellar white matter (85 fmol mg(-1)) and highest in the caudate nucleus (370 fmol mg(-1)), superior colliculus (400 fmol mg(-1)), and anterior thalamic nucleus (588 fmol mg(-1)). The apparent affinity was in the range of 2-6 nM in vitro, predicting high specific binding in PET studies of living brain. However, the distribution volume (V(d), ml g(-1)) of high specific activity [11C]PK11195 was nearly homogeneous (3 ml g(-1)) throughout brain of healthy Landrace pigs, and was nearly identical in studies with lower specific activity, suggesting that factors in vivo disfavor the detection of PBBS in Landrace pigs with this radioligand. In young, adult Göttingen minipig brain, the magnitude of V(d) for [11C]PK11195 was in the range 5-10 ml g(-1), and had a heterogeneous distribution resembling the in vitro findings in Landrace pigs. There was a trend toward globally increased V(d) in a group of minipigs with acute MPTP-induced parkinsonism, but no increase in V(d) was evident in the same pigs rescanned at 2 weeks after grafting of fetal mesencephalon to the partially denervated striatum. Thus, [11C]PK11195 binding was not highly sensitive to constituitively expressed PBBS in brain of young Landrace pigs, and did not clearly demonstrate the expected microglial activation in the MPTP/xenograft model of minipigs.

Quantitative autoradiography of ligands for dopamine receptors and transporters in brain of Göttingen minipig: comparison with results in vivo

The pig has been used as animal model for positron emission tomography (PET) studies of dopamine (DA) receptors and pharmacological perturbations of DA neurotransmission. However, the binding properties of DA receptors and transporters in pig brain have not been characterized in vitro. Therefore, the saturation binding parameters of [3H]SCH 23390 for DA D1 receptors and [3H]raclopride for DA D2/3 receptors were measured by quantitative autoradiography in cryostat sections from brain of groups of 8 week old and adult female Göttingen minipigs. The magnitudes of Bmax and Kd for these ligands were similar in young and old pigs, and were close to those reported for rat and human brain. Furthermore, gradients in the concentrations of D1 and D2/3 sites in striatum measured in vitro agreed with earlier findings in PET studies. However, the dopamine transporter (DAT) ligand [3H]GBR12935 did not bind in pig brain cryostat sections. Whereas the tropane derivative [125I]RTI-55 labeled serotonin transporters (serotonin transporter (SERT)) in pig brain, use of the same ligand under conditions specific for DAT, revealed a pattern of binding similar to that observed for SERT conditions. Parallel studies revealed the presence of DAT in rat and ferret brain. The distribution volume (Vd) of the selective DAT ligand [11C]NS2214 ([11C]Brasofensine) was mapped in groups of normal and MPTP-lesioned Göttingen miniature pigs. The in vivo pattern of Vd matched the distribution of SERT in vitro, and did not differ between the normal pigs and the lesioned animals with documented 60% DA depletions. However, the pattern of specific binding of the selective noradrenaline transporter ligand (S,S)-[11C]MeNER in a single Landrace pig showed that, of the three monoamine transporters, only DAT could not be detected in pig brain. We conclude that the pig is a suitable model for PET studies of DA D1 and D2/3 binding sites, which are fully developed on the eighth postnatal week. However, well-characterized piperazine and tropane radioligands failed to recognize DAT in pig brain; the two tropane radioligands lacked pharmacological specificity for DAT and SERT in pig brain in vitro and in vivo.

Assessment of in vivo MR imaging compared to physical sections in vitro—A quantitative study of brain volumes using stereology

The object of the present study was to compare stereological estimates of brain volumes obtained in vivo by magnetic resonance imaging (MRI) to corresponding volumes from physical sections in vitro. Brains of ten domestic pigs were imaged using a 3-T scanner. The volumes of different brain compartments were obtained from MR images by two observers and from physical sections using the Cavalieri estimator in combination with point counting. Paired t tests revealed no significant differences between the two methods for any of the five compartments considered, except for the basal gray compartment. However, although intraobserver difference of MRI estimates was acceptable, the interobserver difference was not. A statistical highly significant difference of 11-41% was observed between observers for volume estimates of all compartments considered. The study demonstrates that quantitative MRI is susceptible to observer dependent interpretation of images.

Validation of a digital video tracking system for recording pig locomotor behaviour

We are introducing a system for automatically tracking pig locomotor behaviour. Transposing methods for the video-based tracking of rodent behaviour engenders several problems. We have therefore improved existing methods, based on image-subtraction, to offer increased flexibility and accuracy in tracking large-sized animals in situations with a constantly changing background. The improved tracking algorithms introduce a reference frame, which does not include the animal and is automatically updated, and implementation of an automatic threshold detection algorithm. This makes the system more robust to the tracking environment, which could even be of the same colour as the animal, and allows the tracking environment to change during recording. We validated the system by estimating the repeatability, accuracy, and basic noise level, and tested the system in different levels of animal activity evoked by administration of apomorphine (APO) to minipigs in an open field test. Seven pigs each received the vehicle and three doses of APO (0.05, 0.1, and 0.3 mg/kg i.m.), and the locomotor behaviour of each session was recorded for 60-min. The calculated coefficient of repeatability was 0.6%, indicating high repeatability and the basic noise level of the tracking system was estimated to be 2%. Administration of the two lowest doses of APO was accompanied by increased locomotor activity of the pigs. Thus, this digital video-based tracking system for automatically tracking the spontaneous locomotor behaviour of pigs is highly reliable and accurate, and was able to detect well-known effects of APO in pig locomotor activity.

Mapping the amphetamine-evoked dopamine release in the brain of the Göttingen minipig

The availability of dopamine D(2/3) binding sites in brain of six male and six female Göttingen minipigs was measured in a baseline condition and after challenge with amphetamine sulfate (1mg/kg, i.v.) in PET studies with [(11)C]raclopride. Maps of the binding potential (pB; B(max)/K(d)) of [(11)C]raclopride were spatially normalized and co-registered to a common stereotaxic coordinate system for pig brain. The pB maps were then analyzed by volume of interest and voxel-wise comparisons of gender and condition. The mean baseline pB tended to be 10-20% higher in striatum of the female group, but this gender difference was not significant. Variance of the mean baseline pB was higher in the males (44%) than in females (30%), but there was no correlation between pB and individual plasma cortisol or testosterone concentrations. Using statistical parametric mapping, we detected a focus in the right posterior putamen where the magnitude of the amphetamine-evoked decrease in pB was greater in the male than in the female group. Thus, the spatial pattern of reactivity of dopamine D(2/3) receptor availability to amphetamine challenge is not identical in male and female pigs. Within the entire population, the decline in pB evoked by amphetamine (Delta pB) was greater in the ventral striatum (-28%) than in the caudate nucleus (-17%), consistent with earlier reports in monkeys and humans. The magnitude of Delta pB correlated highly with the baseline pB values in all divisions of the striatum. Based upon the principles of competitive binding, the slope of this empirical relationship, f(i), is equal to the fraction of [(11)C]raclopride binding sites sensitive to endogenous dopamine; the magnitude of this fraction ranged from 0.29 in the caudate to 0.36 in the ventral striatum.

Prepulse inhibition of the acoustic startle reflex in pigs and its disruption by d-amphetamine

Prepulse inhibition (PPI) of the startle reflex is an operational measure of sensorimotor gating. The dopamine receptor agonist-mediated disruption of PPI in rats is widely used as a model of the sensorimotor gating deficiencies demonstrated in schizophrenia patients. As a possible tool for validation of a pig model of psychosis, we wished to verify the existence of PPI in landrace pigs and investigate the potential disruption of PPI by d-amphetamine (AMPH) in these animals. PPI of the acoustic startle reflex and its potential disruption by AMPH were investigated using three doses 0.5-1.5mg/kg with a paradigm including two levels of prepulses (82 and 88dB) and a prepulse (PP) interval of 60 and 120ms. We found an average PPI of the startle reflex of 25.6% and both of the investigated PP intensities and PP intervals were equally effective in this PP-inhibitive paradigm. AMPH significantly disrupted PPI and, in spite of only the 0.5mg/kg dose proved statistically significant, the results indicate this to be dose-related. We have demonstrated the phenomenon of PPI of the startle reflex in landrace pigs and its disruption by d-amphetamine. Studies of sensorimotor gating defects could be a valuable additional tool in assessing pig models of neuropsychiatric disorders.

A MRI-compatible stereotaxic localizer box enables high-precision stereotaxic procedures in pigs

We present a nonmagnetic Plexiglas stereotaxic localizer box that can be fitted directly to the pig skull by aluminum screws, allowing stereotaxic MRI or ventriculography and subsequent high-precision stereotaxic procedures. The localizer box was used to target the subthalamic nucleus (STN) bilaterally in five female Göttingen minipigs. Stereotaxic markers were inserted in the pig skull, the head fixated in the localizer box by aluminum screws inserted bilaterally in the zygoma bone with the hard palate locked on a horizontal palate holder. MRI was obtained on a 3T-MR-imager revealing the relation between the inserted markers and the estimated STN-position, and thus the target coordinates. After the MRI, a stereotaxic frame with attached micromanipulator was locked on to the localizer box converting it into a stereotaxic device. The stereotaxic markers were exposed and used as starting point for the stereotaxic procedure, whereby a microelectrode for electrolytic lesioning was inserted in the STN. Postmortem histological analysis revealed 70% correct STN-targeting. The average distance from the lesion center to the STN center was 1.2 mm with a S.D. of 1.1 mm. The most displaced lesion being 3.6 mm from the STN center. We conclude that the described localizer box secure firm head fixation, allowing stereotaxic MRI and subsequent conversion into a stereotaxic device for high-precision stereotaxic procedures.

Gradients of dopamine D1- and D2/3-binding sites in the basal ganglia of pig and monkey measured by PET

The distributions of dopamine D1 and D2/3 binding sites in living brain have not been compared directly using positron emission tomography (PET). To map these binding sites, we first optimized methods for the assay of dopamine receptors in brain of Göttingen miniature pigs. The binding potentials (pB) of [11C]NNC 112 for dopamine D1 receptors and [11C]raclopride for dopamine D2/3 receptors were calculated in pig striatum volumes of interest using metabolite corrected arterial inputs or using cerebellum as a non-binding reference region. Depending upon the method for quantitation, the pB for [11C]NNC 112 was 1.2-5.1 in pig striatum, whereas the pB for [11C]raclopride was 1.0-1.8. We used the reference tissue method of Logan to calculate pB maps for the two tracers. The maps were co-registered to the common stereotaxic space for the pig brain and normalized to a global mean for pB in striatum; t-maps showed that dopamine D1 binding was relatively more abundant in the ventral-anterior striatum of the pig, while dopamine D2/3 binding was greater in the dorsal striatum. Similar comparisons were made for the pBs of [11C]Sch 23390 for dopamine D1 receptors and for [11C]raclopride in the brain of six rhesus monkeys. The magnitudes of pB for both binding sites in monkey brain were close to those in the pig. Consistent with the pig results, there were distinct gradients in the distributions of the two binding sites in monkey brain: D1 binding predominated in the ventral striatum, whereas D2/3 binding was relatively greater in the dorsal-posterior striatum. Gradients of dopamine receptor concentration within the striatum may be a general phenomenon of mammalian brain.

Pre-pulse inhibition of the acoustic startle eye-blink in the Göttingen minipig

Pre-pulse inhibition (PPI) of the startle response is a measure of sensorimotor gating which has been frequently shown to be deficient in schizophrenic patients. In humans it is typically measured as the attenuation of the startle eye-blink reflex EMG when a startle eliciting noise is preceded by a weak white noise pre-pulse (PP), the interval between the PP and the startle noise stimulus (SNS) determining the degree of inhibition. Aiming at developing a new animal model of schizophrenia, we have investigated the acoustic startle eye-blink and PPI in 10 Göttingen minipigs. The stimuli and the block design of the stimulation were similar to paradigms used in human research. Initially the startle habituation across trials and blocks, secondarily the PPI at PP to SNS intervals of 30, 60, 120, 220, 520, 1020 and 2020 ms was investigated. One pig out of ten did not have a startle response, and three other pigs did not have a startle response of a sufficient magnitude to demonstrate the PPI seen in the other six pigs at the expected PP intervals of 60, 120, and 220 ms. Maximal inhibition was seen at the 220 ms interval (mean PPI 58.6%, range -18.4 to 94.6%, N = 9). Most of the results in the pigs are in accordance with findings in studies of the human startle eye-blink EMG and this initial study promotes further studies and the use of the PPI measure in the validation of minipig models of psychiatric disorders.

Minipig negative slow wave demonstrates target/nontarget differences in P300 paradigm

The negative slow wave (NSW) is a late component of the event-related potential (ERP) in man modulated like the P300 by the stimulus, the task, and the response demand. Aiming at the development of a minipig model of schizophrenia, we investigated scalp ERPs in an auditory P300 paradigm in six Göttingen minipigs. Before training, we observed no difference between target and nontarget NSW. After training, target NSW amplitude was increased 50% compared to nontarget. A P350 was recognized, but the finding of a lack of target/nontarget difference is not conclusive.

Semi-micro liquid chromatography of aromatic amino acid metabolites using isocratic elution and column switching

The concentrations of catecholamine-related compounds in body fluids reflect sympathetic nerve functions. Measuring the enzyme activity of these metabolic pathways will improve diagnosis since a variety of symptoms are reported. An isocratic elution system with two column switching valves was developed using three types of semi-micro columns for fast chromatographic analysis of catecholamine related compounds. Columns are a pentyl-bonded phase, 50 x 2.1 mm i.d., a phenylhexyl-bonded phase, 100 x 2.1 mm i.d. and an octadecyl-bonded phase, 100 x 2.1 mm i.d. The separation of 20 standard compounds was achieved within 25 min using reversed-phase ion-pair liquid chromatography with an electrochemical detector. This new system was applied for analysis of catecholamine-related compounds in pig brain, since pigs are a widely used animal model for transgenic manipulation of neural genes, and MHPG (or VMA), DOPAC, DOPA, NE, EP, DA, 5HTP and 5HIAA were quantified.

Stem cells in the treatment of Parkinson's disease

Stem cells have been suggested as candidate therapeutic tools for neurodegenerative disorders, given their ability to give rise to the appropriate cell types after grafting in vivo. In this review I summarize some of the evidence currently available concerning two approaches for the treatment of Parkinson's disease: (1) The generation of dopaminergic neurons from embryonic stem cells, multipotent stem cells, and neuronal progenitor cells for cell replacement therapy. (2) The engineering of multipotent stem cells to release glial cell-line derived neurotrophic factor, a potent neurotrophic factor for dopaminergic neurons, in a neuroprotective and neuroregenerative approach to the treatment of Parkinson's disease.

Normalization of markers for dopamine innervation in striatum of MPTP-lesioned miniature pigs with intrastriatal grafts

As part of the DaNeX study, the uptake and binding of several positron emitting tracers was recorded in brain of healthy Göttingen minipigs, in minipigs with a syndrome of parkinsonism due to MPTP intoxication, and in parkinsonian minipigs which had received intrastriatal grafts of mesencephalic neurons from fetal pigs. The specific binding of [11C]NS 2214 to catecholamine uptake sites was reduced by two thirds in striatum of the intoxicated animals, while the rate constant for the decarboxylation of [18F]fluorodopa was reduced by 50% in the intoxicated animals. Several months after grafting, both pre-synaptic markers of dopamine fibres were normal in striatum. Dopamine depletion or grafting were without effect on the cerebral perfusion rate, measured with [15O]-water, did not alter the rate of oxygen metabolism (CMRO2) in brain, and did not alter the binding potential of tracers for dopamine D1 or D2 receptors in pig striatum. However, the grafting was associated with a local increase in the binding of [11C]PK 11195, a tracer for reactive gliosis, suggesting that an immunological reaction occurs at the site of graft, which might potentially have reduced the graft patency. However, this apparent immunological response did not preclude the re-establishment of normal [18F]fluorodopa and [11C]NS 2214 uptake in the allografted striatum.

Kinetics of the metabolism of four PET radioligands in living minipigs

Most radioligands are substantially metabolised in peripheral organs during the course of positron emission tomography (PET) recordings. Accurate determination of plasma concentrations of unmetabolised radioligands is often important for quantification of data from PET studies. The fractions of untransformed radioligand and radioactive metabolites in plasma extracts must then be measured. Temporal changes in these fractions are influenced by the rate constant of appearance of total radioactive metabolites in plasma (apparent rate constant of metabolism in plasma, k(0)) and the net rate constant of elimination of all radioactive metabolites from plasma (k(-1)). In order to clarify the relationship between radioligand fractions and rate constants, plasma samples collected from Göttingen minipigs during PET recordings using four different binding site ligands were analysed by radio high performance liquid chromatography. The calculated plasma concentrations of parent compounds and their radioactive metabolites were used to calculate k(0) and k(-1) for 11C-labelled NNC 112, NS 2214, PK 11195 and raclopride in minipigs using a novel application of the tissue-slope intercept plot. In general, the apparent rate constant of metabolism in plasma was found to be greater in the minipig than in man. The reported kinetic analysis enables the apparent metabolism of PET radioligands in plasma to be quantified.