The purpose was to analyze the role of dopamine D1 and D2 receptors in conditioned place preference (CPP) of a relatively high dose (5 mg/kg) of methylphenidate (MPH) in adolescent male and female rats, as well as the role of these receptors in the effects of MPH on brain-derived neurotrophic factor (BDNF). The primary mechanism of MPH in the brain is the blockade of the dopamine transporter, yielding an increase of dopamine in the synaptic cleft and is the basis for the rewarding properties of MPH. An initial preference given on postnatal day (P)32 yielded no preference for any context in a three-chambered shuttle box with removable dividers, thus, a biased procedure was used. Conditioning began the day after the initial preference test on P33. On conditioning trials, animals were first administered saline or their respective antagonist (D1 antagonist: 0.1 or 0.2 mg/kg SCH-23390; D2 antagonist: 0.01 or 0.03 mg/kg Eticlopride HCl), followed by methylphenidate (MPH; 5mg/kg). Approximately 10 min after MPH administration, rats were placed into the paired context for a 10 min trial. The choice of the paired context was balanced across animals. In a separate session, all animals received saline in the opposing context. One day post-conditioning on P38, a preference test was administered with dividers removed. Preference was determined through the amount of time spent in the paired context as compared to time spent in the unpaired context on the post-conditioning preference test. One day following the preference test on P39, brain tissue was removed, and nucleus accumbens and striatum analyzed for BDNF. Results showed that MPH produced an increased preference on the post-conditioning preference test that was blocked by either dose of SCH-23390, but was not affected by either dose of eticlopride. Additionally, the higher dose of SCH-23390 resulted in a conditioned place aversion in males, which may be due to the increased presence of dopamine D1 receptors in adolescent males. MPH produced a robust significant increase in BDNF in both nucleus accumbens and striatum, and this increase was alleviated by SCH-23390, but the effect on BDNF is still to be analyzed relative to D2 antagonism. These results show that MPH results in a conditioned place preference in adolescent male and female rats, and these effects appear to be mediated by the dopamine D1 receptor. Further, MPH results in a significant increase of BDNF in drug reward areas of the brain, which has implications towards synaptic plasticity in these regions in response to MPH.

This study analyzed the role of dopamine D1 and D2 receptors in methylphenidate (MPH) conditioned place preference (CPP) in adolescent male and female rats, in addition to the role of these receptors in the effects of MPH on brain-derived neurotrophic factor (BDNF) in the dorsal striatum and nucleus accumbens. Using a nonbiased CPP procedure, the animals were conditioned from postnatal day (PD) 33 to 37. On conditioning trials, animals were first administered saline or their respective antagonist (0.1 or 0.2 mg/kg SCH-23390; 0.01 or 0.03 mg/kg eticlopride HCl), followed by MPH (5 mg/kg). Approximately 10 min after MPH administration, the rats were placed into the paired context for a 10-min trial. One day after conditioning on PD38, a preference test was administered with dividers removed. One day following the preference test on PD39, brain tissue was removed, and the nucleus accumbens and striatum were analyzed for BDNF. Results revealed that MPH conditioning resulted in an increased preference that was blocked by either dose of SCH-23390, but generally not affected by either dose of eticlopride. Further, the higher dose of SCH-23390 resulted in a conditioned place aversion in males, presumably due to an increased number of dopamine D1 receptors in adolescent males. MPH produced a significant increase of striatal and accumbal BDNF alleviated by SCH-23390 or eticlopride. These results show that MPH results in CPP in adolescent male and female rats and these effects appear to be mediated by the dopamine D1 receptor, but the effects of MPH on BDNF appear to be mediated by both dopamine receptor families.

Methylphenidate (MPH) is a psychostimulant that is used for the treatment of attention-deficit hyperactivity disorder that is often recreationally abused. Past studies have primarily analyzed the effects of MPH on behavior and BDNF using males as subjects, with studies showing a lack of behavioral sensitization, although the effect of MPH on BDNF has yielded contradictory results. BDNF is a neurotrophin ubiquitously found throughout the brain that plays an important role in synaptic maintenance and development and has been implicated in addiction. This study analyzed sex differences in induction and expression of MPH locomotor sensitization in adolescent male and female rats as well as the effects of MPH on BDNF protein in two brain areas of drug reward: the nucleus accumbens (NAcc) and striatum (STR), after both induction and expression of sensitization. After habituation to a locomotor arena, animals (N=6-8 per group) were administered MPH (5 mg/kg) or saline every other day from postnatal day (P)33 to 49 and tested for 30 min in the same arena with activity counts recorded. In one group, brain tissue was removed one day following testing and the NAcc and STR assayed for BDNF at P50. A different group of animals was raised to P60 and given an MPH (or saline) challenge. One day following the challenge, brain tissue was removed and the NAcc and STR were assayed for BDNF at P61. Females administered MPH demonstrated behavioral sensitization from P33 to P41, and then decreased in activity from P41 to P49. Females demonstrated a robust increase in locomotor activation as compared to males, which failed to demonstrate sensitization to MPH. However, both groups given MPH demonstrated an increase in activity compared to controls throughout sensitization testing. On the challenge at P60, females administered MPH demonstrated higher levels of activity compared to all other groups and were equivalent to their final day of sensitization. Males administered MPH also expressed sensitization, as they demonstrated increased behavioral activation as compared to saline-treated controls. Neurochemical analyses at P50 revealed that MPH produced a significant increase in striatal BDNF in males, but a significant decrease in striatal BDNF in females. There were no changes in the NAcc. At P61, BDNF was increased in both STR and NAcc in males, and female data will be presented. These data demonstrate robust sex differences in behavioral activation and sensitization to MPH that is both induced and expressed in females, but only expressed in males. Further, MPH produces sex-dependent effects on BDNF, indicating sex differences in the brain plasticity response to MPH in adolescence.

This study analyzed locomotor sensitization to methylphenidate (MPH, Trade name: Ritalin) in adolescent male and female rats. Females, but not males, demonstrated locomotor sensitization. Interestingly, females given MPH demonstrated a significant decrease of brain derived neurotrophic factor (BDNF) in the striatum, whereas males demonstrated an increase in this same brain area.

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor involved in synaptic differentiation, growth, and maintenance. Increases in BDNF have been shown in substance abuse and decreases in BDNF have been shown in response to stress and major depressive disorder (MDD). We analyzed the effects of BDNF upregulation via lentivirus on Pavlovian conditioned approach (PCA), behavioral sensitization, and nicotine self-administration in rats. Lentiviral-mediated expression cassettes, with dual promoters to drive the BDNF gene and the reporter gene were constructed according to the manufacturer’s instruction and surgically injected into the nucleus accumbens (Nac), the primary brain area that mediates drug reward and reinforcement. Rats were allowed to recover for three weeks before behavioral testing commenced. All rats were trained to associate the presentation of a lever and illumination of a stimulus light with delivery of 20% sucrose in a Pavlovian conditioned approach (PCA) task. Head entries into the receptacle where sucrose was delivered (goal tracking) and lever pressing (sign tracking) during the conditioned stimulus (CS) were measured to determine if BDNF over-expression (BDNF+) altered approach to the sign or goal location. Rats in the BDNF+ group made more goal directed behaviors during the CS than sham group. There were no differences in sign tracking and no differences in basal activity. This pattern suggests that BDNF over-expression may increase reward-related learning in a manner specific to goal tracking. Three days after completion of the PCA task, all animals were habituated to a locomotor arena followed by nicotine behavioral sensitization, and were administered nicotine (ip, 0.5 mg/kg free base) or saline every second day for seven days. Results revealed that the BDNF+ group demonstrated enhanced sensitivity to the hypoactive response to nicotine. At day 7, BDNF+ animals demonstrated enhanced behavioral sensitization to nicotine as compared to all other groups, and Sham NIC animals demonstrated sensitization compared to Sham SAL controls. Thus, it appears increasing NAc BDNF expression enhances the behavioral response to nicotine. Animals were then surgically implanted with a jugular catheter and commenced nicotine self-administration. Interestingly, BDNF+ rats demonstrated reduced nicotine self-administration and motivation to obtain nicotine. Global changes in BDNF expression could be a mediating variable in endophenotypes that are more or less susceptible to drug-taking and substance dependence.

Unsere Bemühungen die Natur individueller Unterschiede der Emotionsregulation zu verstehen, involviert das Verständnis der Gene. In dieser Arbeit werden Gene (Kandidatengene), die für Proteine als Rezeptoren, Transporter oder Enzyme im Neurotransmitterstoffwechsel Serotonin und Dopamin kodieren, untersucht. Serotonin und Dopamin sind mit Angststörungen in verschiedener Weise assoziiert. Sie sind wichtige Neurotransmitter in Teilen des Gehirns, die mit Angstkonditionierung im Zusammenhang stehen. Polymorphismen in diesen Genen verändern die Struktur und Funktion der Genprodukte und nehmen damit Einfluss auf die Funktion von Hirnstrukturen und -systemen. Phobien sind äußerst intensive und persistente Furchtreaktionen, welche durch spezifische Situationen oder Objekte ausgelöst werden und von dem zwingenden Wunsch begleitet sind, diese Situationen oder Objekte zu vermeiden. Die Intensität der Furchtreaktion erscheint einem Außenstehenden, entsprechend der realen Gefahr dieser Situation, unangemessen und eigentümlich. Zumeist hat der Phobiker selbst auch Einsicht in diese Irrationalität seiner Furchtreaktion, vermag sie aber nicht willentlich unter Kontrolle zu halten. In dieser Arbeit wurden als Beispiel einer assoziierten Angst die Zahnbehandlungsphobie und als Beispiel einer nicht-assoziierten Angst die Spinnenphobie untersucht. Es wurden 53 Zahnbehandlungsängstliche, 52 Spinnenphobiker und 37 Kontrollpersonen mittels Fragebogen (SPF,FAS,STAI trait, DCQ, DFS, ASI, PANAS, R-IDCI) getestet. Die Probanden wurden durch PCR-Analyse von Mundschleimhautabstriche je einem Polymorphismus der untersuchten Kandidatengene zugeordnet. Es handelte sich dabei um die Gene für den Serotonintransporter 5HTT, den Serotoninrezepor 5HT1A, den Dopaminrezeptor DRD4, den Dopamintransporter DAT, BDNF und das in den Katecholaminabbau involvierte COMT-Enzym. Die untersuchten Polymorphismen weisen in der Literatur einen Einfluss auf die Angstausprägungen auf. In der statistischen Auswertung wurde auf signifikante Zusammenhänge zwischen einem Polymorphismus und der Ausprägung einer Phobie geachtet. Desweiteren wurden die verschiedenen Polymorphismen mit den Ergebnissen der Fragebogentests in Zusammenschau gebracht. Ein direkter Einfluss eines der untersuchten Gene auf die Ausprägung einer Phobie konnte nicht nachgewiesen werden. In der Gruppe der Dentalphobiker zeigten sich Hinweise auf einen Einfluss des BDNF G-Allels und des COMT G-Allels auf erhöhte Ängstlichkeit. / Understanding of individual differences in emotions is related to the understanding of genes. This paper analyses genes (candidate genes) that code for proteins as receptors, transporters or enzymes in the metabolism of neurotransmitter serotonin and dopamine. Serotonin and dopamine are in different ways associated with anxiety disorders. They are important neurotransmitter in parts of the brain that are associated with anxiety conditioning. Polymorphisms in these genes change the structure and function of gene products and have effect on the function of brain structures. In literature the analysed polymorphisms show influence on characteristics of anxiety. Phobias are very intense and persistent fearreactions, which are triggered by specific situations or objects. They are accompanied by the desire to avoid these specific objects/situations. The intensity of this fearreactions seems inadequate according to real danger. The phobic person himself realises the irrationality of the reaction, but cannot control it. In this paper dental phobia, as an example for associated anxiety, and spider phobia, as an example for non-associated anxiety, are analysed. 53 dentalphobic, 52 spiderphobic and 37 control persons are tested by questionnaires (SPF,FAS,STAI trait, DCQ, DFS, ASI, PANAS, R-IDCI). The test persons were related to each one polymorphism of a candidate gene by PCR-analysing of mouth mucosa samples. Analysed candidate genes are serotonin-transporter 5HTT, serotonin-receptor 5HT1A, COMT, dopamine-receptor DRD4, dopamine-transporter and neutrophin BDNF. The relationship between a polymorphism and the characteristics of a phobia was examined statistically. Further the questionnaire results and polymorphisms were analysed for relations. No direct influence could be shown for candidate genes on phobia characteristics. In the group of dental phobia, hints for influence of the BFNF G-allele and COMT G-allele on anxiety could be made.

In this study I investigate the role of Schwann cell and axon-derived trophic signals as modifiers of axonal integrity and sprouting in motoneuron disease and diabetic neuropathy (DNP). The first part of this thesis focuses on the role of the Schwann-cell-derived ciliary neurotrophic factor (CNTF) for compensatory sprouting in a mouse model for mild spinal muscular atrophy (SMA). In the second part, the role of the insulin-like growth factor 1 (IGF-1) and its binding protein 5 (IGFBP-5) is examined in the peripheral nerves of patients with DNP and in two corresponding mouse models. Proximal SMA is caused by homozygous loss or mutation of the SMN1 gene on human chromosome 5. The different forms of SMA can be divided into four groups, depending on the levels of SMN protein produced from a second SMN gene (SMN2) and the severity of the disease. Patients with milder forms of the disease, type III and type IV SMA, normally reach adulthood and regularly show enlargement of motor units, signifying the reinnervation of denervated muscle fibers. However, the underlying mechanisms are not understood. Smn+/- mice, a model of type III/IV SMA, are phenotypically normal, but they reveal progressive loss of motor neurons and denervation of motor endplates starting at 4 weeks of age. The progressive loss of spinal motor neurons reaches 50% at 12 months but muscle strength is not reduced. The first evidence for axonal sprouting as a compensatory mechanism in these animals was the more than 2-fold increase in amplitude of single motor unit action potentials (SMUAP) in the gastrocnemius muscle. Confocal analysis confirmed pronounced sprouting of innervating motor axons. As CNTF is highly expressed in Schwann cells and known to be involved in sprouting, its role for this compensatory sprouting response and the maintenance of muscle strength in Smn+/- mice was investigated. Deletion of CNTF in this mouse model results in reduced sprouting and decline of muscle strength in Smn+/- Cntf-/- mice. These findings indicate that CNTF is necessary for a sprouting response and thus enhances the size of motor units in skeletal muscles of Smn+/- mice. DNP afflicting motor and sensory nerve fibers is a major complication in diabetes mellitus. The underlying cellular mechanisms of motor axon degeneration are poorly understood. IGFBP-5, an inhibitory binding protein for IGF-1, is highly upregulated in peripheral nerves in patients with DNP. The study investigates the pathogenic relevance of this finding in transgenic mice overexpressing IGFBP-5 in motor axons. These mice develop motor axonopathy similar to that seen in DNP. Motor axon degeneration is also observed in mice in which the IGF-1 receptor (IGF-1R) was conditionally depleted in motoneurons, indicating that reduced activity of IGF-1 on IGF-1R in motoneurons is responsible for the observed effect. These data provide evidence that elevated expression of IGFBP-5 in diabetic nerves reduces the availability of IGF-1 for IGF-1R on motor axons leading to progressive neurodegeneration, and thus offers novel treatment strategies. / In dieser Arbeit habe ich die Rolle der neurotrophen Faktoren Ciliary neurotrophic factor (CNTF) und Insulin-like-growth factor 1 (IGF-1), die in Schwannzellen gebildet werden, als Modulatoren der axonalen Integrität bei einer degenerativen Motoneuronenerkrankung und bei diabetischer Neuropathie (DNP) untersucht. Im ersten Teil dieser Arbeit wird gezeigt, dass CNTF für ein kompensatorisches Sprouting von motorischen Axonen in einem Mausmodell für spinale Muskelatrophie (SMA) verantwortlich ist. Im zweiten Teil wird die Rolle von IGF-1 und dessen Bindeprotein, IGFBP-5, in Axonen motorischer Nerven bei Patienten mit DNP und zwei korrespondieren Mausmodellen gezeigt. Die proximale SMA wird durch einen homozygoten Verlust oder Mutation des SMN1 Gens auf dem Chromosom 5 verursacht. Bei der spinalen Muskelatrophie unterscheidet man verschiedene Schweregrade, abhängig von der Menge an SMN Protein, das vom zweiten SMN Gen (SMN2) produziert werden kann. Patienten mit einer milderen Form von SMA (Typ III und IV) erreichen das Erwachsenenalter und zeigen oft vergrößerte motorische Einheiten, im Gegensatz zu Patienten mit den schweren kindlichen Formen der Erkrankung. Smn+/- Mäuse, ein Modell für die leichten SMA Formen Typ II und IV, zeigen denervierte Endplatten bereits 4 Wochen nach der Geburt und einen fortschreitenden Verlust von Motoneuronen, der nach 12 Monaten mehr als 50% beträgt, ohne dass sich die Muskelkraft der Tiere verringert. Die Amplitude der Summenpotenziale von einzelnen motorischen Einheiten (Single motor unit action potential, SMUAP) im Wadenmuskel ist mehr als 2-fach erhöht. Konfokale Aufnahmen bestätigen ausgeprägtes Sprouting der noch innervierenden Axone. Smn+/- Mäuse ohne CNTF, das normalerweise stark in Schwann-Zellen exprimiert ist, zeigen reduziertes Sprouting und verringerte Muskelkraft. Diese Ergebnisse sprechen dafür, dass CNTF für das Sprouting und die vergrößerten motorischen Einheiten in Smn+/- Mäusen verantwortlich ist. Dieser kompensatorische Mechanismus könnte neue Behandlungs-möglichkeiten für Motoneuronerkrankungen eröffnen. Die Diabetische Neuropathie (DNP), eine der Hauptkomplikationen bei Diabetes Mellitus, betrifft sowohl motorische als auch sensorische Nervenfasern. Die zugrunde liegenden zellulären Mechanismen, die zur Degeneration motorischer Axone in Spätstadien der Erkrankung führen, sind größtenteils noch ungeklärt. IGFBP-5, ein IGF-1 hemmendes Bindeprotein, ist in peripheren Nervbiopsien von DNP Patienten stark überexprimiert. Diese potenzielle pathogene Relevanz wurde bei IGFBP-5 überexprimierenden transgenen Mäusen untersucht. Diese Mäuse entwickeln ähnlich wie die DNP Patienten eine motorische Axonopathie. Diese Axondegeneration zeigen auch Mäuse, bei denen der IGF-1 Rezeptor (IGF-1R) neuronenspezifisch ausgeschaltet wurde. Das bedeutet, dass reduzierte Wirkung von IGF-1 am IGF-1R auf Axonen von Motoneuronen für die beobachtete Axonopathie verantwortlich ist. Zusammenfassend zeigen diese Daten, dass erhöhtes IGFBP-5 in diabetischen Nerven die Verfügbarkeit von IGF-1 für den IGF-1R reduziert und zu progressiver Neurodegeneration führt. Diese Erkenntnis könnte neue Behandlungsstrategien für Patienten mit DNP eröffnen.

Abstract not available

<p>The symptoms of Parkinson's disease occur due to degeneration of dopamine neurons in substantia nigra. It has been demonstrated that glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor when it comes to protect and enhance survival of dopamine neurons in animal models of Parkinson's disease. The aim of this study was to evaluate short- and long-term effects of GDNF on survival and nerve fiber outgrowth of dopamine cells and astrocytic migration in mouse fetal ventral mesencephalic (VM) tissue. Primary tissue cultures were made of mouse fetal VM tissue and evaluated at 7 and 21 days in vitro (DIV) in terms of dopaminergic nerve fiber outgrowth and astrocytic migration when developed with GDNF present, partially, or completely absent. The results revealed that VM tissue cultured in the absence of GDNF did not exhibit any significant differences in migration of astrocytes or dopaminergic nerve fiber outgrowth neither after 7 DIV nor after 21 DIV, when compared with tissue cultured with GDNF present. Migration of astrocytes and dopaminergic nerve fiber outgrowth reached longer distances when tissue was left to develop for 21 DIV in comparison with 7 DIV. In order to study the long-term effects of GDNF, mouse fetal dopaminergic tissue was transplanted into the ventricles of adult mice and evaluated after 6 months. No surviving dopamine neurons were present in the absence of GDNF. In contrast dopamine neurons developed with GDNF did survive, indicating that GDNF is an essential neurotrophic factor when it comes to long-term dopamine cell survival. More cases have to be assessed in the future in order to strengthen the findings. Thus, transplanted dopamine neurons will be assessed after 3 and 12 months in order to map out when dopamine neurons deprived of GDNF undergo degeneration.</p>

<p>The focus of this thesis is the life and death of adult retinal ganglion cells (RGCs). RGCs are neurons that convey visual information from the retina to higher centers in the brain. If the optic nerve is transected (ONT), adult RGCs die by a form of cell death called apoptosis, and a general hypothesis is that neurotrophic factors can support the survival of injured neurons.</p><p>With the intention to gain knowledge about systems that can be used to decrease RGC death after ONT, we have studied growth factor receptors belonging to the tyrosine kinase family of receptors (RTK), known to mediate important cell survival signals. We found that the RTK Ret and its coreceptor GFRα1 were expressed by RGCs, and to test the above-mentioned hypothesis, we intraocularly administered glial cell-line derived factor, which activates a Ret-GFRα1 complex, and found transiently mediated RGC survival after ONT. </p><p>To identify new, potential neurotrophic factor receptors expressed by RGCs, with the aim to improve RGC survival after ONT, we developed a method for the molecular analysis of acutely isolated RGCs. The method involves retrograde neuronal tracing, mechanical retinal layer-separation, and isolation of individual RGCs under UV-light for RT-PCR analysis. Using this method, in combination with degenerate PCR directed towards the tyrosine kinase domain, several RTKs were identified. Axl, Sky, VEGFR-2, VEGFR-3, CSF-1R, and PDGF-βR are expressed by adult RGCs, and considered to be receptors with potential neurotrophic activity. Other results have shown that RGCs may require depolarization or increase in intracellular cAMP levels in order to fully respond to exogenously added trophic factors. We found that melanocortin receptors (MCRs) were expressed by RGCs, and MCRs can mediate elevation of intracellular AMP. We observed that α-MSH induced neurite outgrowth from embryonic retinal cells, indicating that MCR ligands have direct effects on retinal cells. RTKs and their ligands may be involved in endogenous systems for neuronal repair within the visual system. BDNF, NT-3, FGF2, and HGFR all increased in the retina after ONT and may be a part of an activated system for neuronal repair locally within the retina. </p><p>Adult axotomized RGCs die by apoptosis, therefore we examined the regulation of apoptotic genes after ONT. Bim and Bax increased in the retina after ONT, and may promote death of axotomized RGCs, whereas the increase in Bcl-2 may contribute to limit RGC apoptosis after ONT. </p><p>All in all, this thesis provides insights into the expression and regulation of molecules involved in the death and survival of RGCs. The results have revealed a number of potential neurotrophic receptors expressed by RGCs, and both identified RTKs and MCRs will serve as new targets in therapeutic approaches aiming at counteraction of RGC death after injury.</p>