Selective and Divergent Regulation of Cortical 5-HT 2A Receptors in Rabbit ABBREVIATIONS: 5-HT 2 , 5-hydroxytryptamine 2

ABSTRACT It is well established that repeated administration of both 5-hydroxytryptamine 2 (5-HT 2 ) receptor agonists and antagonists decreases the density of 5-HT 2A and 5-HT 2C receptors. However, the regulation of these two receptors has not been studied in the same tissue. Therefore, we examined the effects of repeated daily injections of the 5-HT 2 receptor agonists (Ϯ)-2,5-dimethoxy-4-iodoamphetamine (DOI) and D-lysergic acid diethylamide (LSD) and the antagonists d-2-bromolysergic acid diethylamide hydrogen tartrate (BOL) and ␣-phenyl-2-(2-phenylethyl)-4-piperidinemethanol (MDL 11,939) on rabbit cortical 5-HT 2A and 5-HT 2C receptors. Repeated administration of DOI, LSD, or BOL decreased cortical 5-HT 2A receptor density but had no effect on the density of cortical 5-HT 2C receptors. Numerous researchers have demonstrated in vivo that both 5-hydroxytryptamine 2 (5-HT 2 ) agonist and antagonists down-regulate 5-HT 2A and 5-HT 2C receptors (for reviews, see Although, in vivo, 5-HT 2 agonists and antagonists are capable of down-regulating both 5-HT 2A and 5-HT 2C receptors, the previously reported receptor changes have been measured in different brain regions. Regulation of 5-HT 2A receptors has mainly been studied in the cortex, whereas regulation of 5-HT 2C receptors has been investigated in choroid plexus, brain stem, and spinal cord. Thus, these studies have not addressed the question of whether the regulation of these two receptors occurs in a coordinated manner within the same brain region. In the one case of antagonist-induced 5-HT 2A receptor up-regulation, the effect of SR 46349B on the 5-HT 2C receptor was not examined We examined the effects of several 5-HT 2 receptor agonist

A strategy for the generation, characterization and distribution of animal models by The Michael J. Fox Foundation for Parkinson’s Research

Progress in Parkinson’s disease (PD) research and therapeutic development is hindered by many challenges, including a need for robust preclinical animal models. Limited availability of these tools is due to technical hurdles, patent issues, licensing restrictions and the high costs associated with generating and distributing these animal models. Furthermore, the lack of standardization of phenotypic characterization and use of varying methodologies has made it difficult to compare outcome measures across laboratories. In response, The Michael J. Fox Foundation for Parkinson’s Research (MJFF) is directly sponsoring the generation, characterization and distribution of preclinical rodent models, enabling increased access to these crucial tools in order to accelerate PD research. To date, MJFF has initiated and funded the generation of 30 different models, which include transgenic or knockout models of PD-relevant genes such as Park1 (also known as Park4 and SNCA), Park8 (LRRK2), Park7 (DJ-1), Park6 (PINK1), Park2 (Parkin), VPS35, EiF4G1 and GBA. The phenotypic characterization of these animals is performed in a uniform and streamlined manner at independent contract research organizations. Finally, MJFF created a central repository at The Jackson Laboratory (JAX) that houses both non-MJFF and MJFF-generated preclinical animal models. Funding from MJFF, which subsidizes the costs involved in transfer, rederivation and colony expansion, has directly resulted in over 2500 rodents being distributed to the PD community for research use

Loss of Leucine-rich Repeat Kinase 2 (LRRK2) in Rats Leads to Progressive Abnormal Phenotypes in Peripheral Organs

The objective of this study was to evaluate the pathology time course of the LRRK2 knockout rat model of Parkinson’s disease at 1-, 2-, 4-, 8-, 12-, and 16-months of age. The evaluation consisted of histopathology and ultrastructure examination of selected organs, including the kidneys, lungs, spleen, heart, and liver, as well as hematology, serum, and urine analysis. The LRRK2 knockout rat, starting at 2-months of age, displayed abnormal kidney staining patterns and/or morphologic changes that were associated with higher serum phosphorous, creatinine, cholesterol, and sorbitol dehydrogenase, and lower serum sodium and chloride compared to the LRRK2 wild-type rat. Urinalysis indicated pronounced changes in LRRK2 knockout rats in urine specific gravity, total volume, urine potassium, creatinine, sodium, and chloride that started as early as 1- to 2-months of age. Electron microscopy of 16-month old LRRK2 knockout rats displayed an abnormal kidney, lung, and liver phenotype. In contrast, there were equivocal or no differences in the heart and spleen of LRRK2 wild-type and knockout rats. These findings partially replicate data from a recent study in 4-month old LRRK2 knockout rats and expand the analysis to demonstrate that the renal and possibly lung and liver abnormalities progress with age. The characterization of LRRK2 knockout rats may prove to be extremely valuable in understanding potential safety liabilities of LRRK2 kinase inhibitor therapeutics for treating Parkinson’s disease

The GBA1 D409V mutation exacerbates synuclein pathology to differing extents in two alpha-synuclein models.

Heterozygous mutations in the GBA1 gene - encoding lysosomal glucocerebrosidase (GCase) - are the most common genetic risk factors for Parkinson\u27s disease (PD). Experimental evidence suggests a correlation between decreased GCase activity and accumulation of alpha-synuclein (aSyn). To enable a better understanding of the relationship between aSyn and GCase activity, we developed and characterized two mouse models that investigate aSyn pathology in the context of reduced GCase activity. The first model used constitutive overexpression of wild-type human aSyn in the context of the homozygous GCase activity-reducing D409V mutant form of GBA1. Although increased aSyn pathology and grip strength reductions were observed in this model, the nigrostriatal system remained largely intact. The second model involved injection of aSyn preformed fibrils (PFFs) into the striatum of the homozygous GBA1 D409V knock-in mouse model. The GBA1 D409V mutation did not exacerbate the pathology induced by aSyn PFF injection. This study sheds light on the relationship between aSyn and GCase in mouse models, highlighting the impact of model design on the ability to model a relationship between these proteins in PD-related pathology

Decreased glucocerebrosidase activity and substrate accumulation of glycosphingolipids in a novel GBA1 D409V knock-in mouse model.

Multiple mutations have been described in the human GBA1 gene, which encodes the lysosomal enzyme beta-glucocerebrosidase (GCase) that degrades glucosylceramide and is pivotal in glycosphingolipid substrate metabolism. Depletion of GCase, typically by homozygous mutations in GBA1, is linked to the lysosomal storage disorder Gaucher's disease (GD) and distinct or heterozygous mutations in GBA1 are associated with increased Parkinson's disease (PD) risk. While numerous genes have been linked to heritable PD, GBA1 mutations in aggregate are the single greatest risk factor for development of idiopathic PD. The importance of GCase in PD necessitates preclinical models in which to study GCase-related mechanisms and novel therapeutic approaches, as well as to elucidate the molecular mechanisms leading to enhanced PD risk in GBA1 mutation carriers. The aim of this study was to develop and characterize a novel GBA1 mouse model and to facilitate wide accessibility of the model with phenotypic data. Herein we describe the results of molecular, biochemical, histological, and behavioral phenotyping analyses in a GBA1 D409V knock-in (KI) mouse. This mouse model exhibited significantly decreased GCase activity in liver and brain, with substantial increases in glycosphingolipid substrates in the liver. While no changes in the number of dopamine neurons in the substantia nigra were noted, subtle changes in striatal neurotransmitters were observed in GBA1 D409V KI mice. Alpha-synuclein pathology and inflammation were not observed in the nigrostriatal system of this model. In summary, the GBA1 D409V KI mouse model provides an ideal model for studies aimed at pharmacodynamic assessments of potential therapies aiming to restore GCase

The hTH-GFP Reporter Rat Model for the Study of Parkinson's Disease

<div><p>Parkinson disease (PD) is the second leading neurodegenerative disease in the US. As there is no known cause or cure for PD, researchers continue to investigate disease mechanisms and potential new therapies in cell culture and in animal models of PD. In PD, one of the most profoundly affected neuronal populations is the tyrosine hydroxylase (TH)-expressing dopaminergic (DA) neurons of the substantia nigra pars compacta (SNpc). These DA-producing neurons undergo degeneration while neighboring DA-producing cells of the ventral tegmental area (VTA) are largely spared. To aid in these studies, The Michael J. Fox Foundation (MJFF) partnered with Thomas Jefferson University and Taconic Inc. to generate new transgenic rat lines carrying the human TH gene promoter driving EGFP using a 11 kb construct used previously to create a hTH-GFP mouse reporter line. Of the five rat founder lines that were generated, three exhibited high level specific GFP fluorescence in DA brain structures (ie. SN, VTA, striatum, olfactory bulb, hypothalamus). As with the hTH-GFP mouse, none of the rat lines exhibit reporter expression in adrenergic structures like the adrenal gland. Line 12141, with its high levels of GFP in adult DA brain structures and minimal ectopic GFP expression in non-DA structures, was characterized in detail. We show here that this line allows for anatomical visualization and microdissection of the rat midbrain into SNpc and/or VTA, enabling detailed analysis of midbrain DA neurons and axonal projections after toxin treatment in vivo. Moreover, we further show that embryonic SNpc and/or VTA neurons, enriched by microdissection or FACS, can be used in culture or transplant studies of PD. Thus, the hTH-GFP reporter rat should be a valuable tool for Parkinson's disease research.</p></div