京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20998号 / 医博第4344号 / 新制||医||1027(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 伊佐 正, 教授 渡邊 直樹, 教授 髙橋 良輔 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Food choice is a modifiable health factor which involves neural, hormonal, and metabolic signals. The lateral parabrachial nucleus is a brain structure in the pons that integrates multiple aspects of food choice. It receives information from the homeostatic melanocortin hypothalamic system and projects to the mesolimbic dopamine reward system. The lateral parabrachial is molecularly diverse and expresses the acetylcholine synthesis enzyme: choline acetyltransferase (ChAT). In this study, we used ChAT-CRE mice to investigate the anatomical projections, the calcium dynamics, and the causal role of the LPBN ChAT neurons. Anatomical projection results were produced using CRE dependent viral vectors to express mRuby tagged synaptophysin, the highest output being the central amygdala. Calcium dynamics were measured at the amygdala using the genetically encoded calcium indicator GCaMP. The dynamics around the decision to consume food were seen to be different between fasted and sated satiety states. Activation of the circuit showed a pronounced latency to food consumption and time to finish for a single calorie of food. These data demonstrate a possible node that integrates homeostatic feeding information and relays it to higher order brain systems that modify reward value. / Master of Science / Health can be impacted by the food an individual decides to eat, and this choice is controlled by the brain. There are many regions of the brain that are recruited when an individual decides to eat, but the two major circuits recruited are the homeostatic feeding circuit and the reward feeding circuit. The homeostatic feeding circuit involves the hypothalamus, the structure that controls basic essential functions of the body and circulating hunger hormones to signal energy availability. The second circuit is the reward circuitry which uses the neurotransmitter dopamine to signal pleasure and motivation for food. At the middle of the two circuits sits the parabrachial nucleus which expresses choline acetyltransferase, the enzyme that creates the neurotransmitter acetylcholine. To harness the molecular and anatomical specificity, we employed viral dependent protein expression to measure the anatomical output, the activity when a mouse is engaged in feeding behavior, and the causal role of the identified circuit during feeding behavior. The results showed the anatomical output to be the central amygdala, a modifier of food reward and value. The activity of the cells while feeding was seen to be higher when sated, and the activation of the circuit saw an increased latency to eat food and increased the time to consume a calorie. Together, we have demonstrated a circuit from the parabrachial nucleus the amygdala which integrates homeostatic information and projects to a brain structure that modifies food value and reward.

Parkinson’s disease (PD) is among the most devastating neurodegenerative disorders, and affects 1% of the global population above the age of 60. Several mechanisms have been proposed to explain the dopamine degeneration exhibited in PD: mitochondrial dysfunction, and endoplasmic reticulum (ER) stress. Inaccurate diagnosis is one of the greatest challenges to treatment of PD. Currently, there is no standard diagnostic test for PD. Neurotrophic factors (NTF) are secreted proteins that promote survival and maintenance of neurons during development. The loss of NTFs for specific neuronal populations could confer susceptibility to various neurodegenerative disorders. Cerebral dopamine neurotrophic factor (CDNF) is a novel NTF selective for dopamine neurons. CDNF has demonstrated profound neuroprotective and neurorestorative effects on dopamine neurons in well established animal models of PD. Presently, there are no studies examining endogenous levels of CDNF in PD models or clinical populations of PD, prompting the present study. Findings will bring insight into the neurobiological mechanisms underlying neurodegeneration in PD. This study has determined that CDNF protein and mRNA expression is not altered following 6-OHDA lesioning, suggesting a compensatory mechanism of CDNF in response to injury. We have also determined that CDNF mRNA expression declines with age, which could confer susceptibility to developing neurodegenerative diseases such as PD. In clinical populations of PD, platelets showed a significant increase in CDNF mRNA expression that was not seen in lymphocytes or whole blood. This suggests a role of CDNF in PD, specifically for platelets; however, it is important to delineate whether this increase is the result of treatment. Incidentally, we found that CDNF mRNA expression is significantly reduced following stroke. Together, these results stress the importance of CDNF in disorders stemming from ER stress. Future studies should examine the role of CDNF in preclinical models of stroke, as well as knockout models of PD. / Thesis / Master of Science (MSc)

Ontogenetic dopaminergic denervation of rat forebrain is associated with latent supersensitization of dopamine (DA) receptors that is unmasked only by a priming process entailing repeated DA agonist treatments. Similar denervation supersensitivity holds for serotonin (5-HT) and most other neurochemical systems. Because DA and 5-HT neurons compete for target sites in the brain and mimic or replicate actions of the others, we investigated the modulatory influence of DA neurons on 5-HT receptor sensitivity; and role of 5-HT neurons in modulating DA receptor sensitivity. In these studies rats were lesioned with the DA neurotoxin B-hydroxydopamine (6-OHDA, icv; desipramine pretreatment) or 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT, icv; desipramine pretreatment) either at 3 days after birth or in adulthood. Responses to DA and 5-HT agonists were determined in several behavioral paradigms in adulthood. In assessing oral responses to agonists, we found that the D1 agonist (±)-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol (SKF 38393) profoundly induced activity if rats were lesioned neonatally with 6-OHDA, but not if rats were co-lesioned as neonates or as adults with 5,7-DHT. The D2 agonist quinpirole induced profound oral activity, but only if rats were lesioned as neonates with 5,7-DHT; or if rats were lesioned with both 6-OHDA (neonatally administered) and 5,7-DHT (adult stage). In all rats lesioned as neonates with 6-OHDA, the 5-HT2 agonist m-chlorophenylpiperazine produced enhanced activity, regardless of 5,7-DHT treatment. These findings demonstrate that DA neurons modulate receptor sensitivity status of both DA and 5-HT receptors; and 5-HT neurons do so similarly. This phenomenon is pertinent to animal models of human disorders and in the syndrome spectrum and treatment approach of human neurodegenerative disorders (e.g. parkinsonism, tardive dyskinesia), developmental disorders (e.g. hyperkinetic activity) and psychiatric disorders.

Repeated ontogenetic treatment with quinpirole produces enhanced quinpirole-induced yawning and antinociceptive actions in adult rats. We now report the occurence of a bizarre behavior jumping inrats so treated. Rats were treated daily from birth with quinpirole HCl (3.0 mg/kg per day × 28 days i.p., salt form) or saline vehicle. After each daily injection, the rats were observed for at least 1 h. Starting on the 18th day after birth, quinpirole treatment was associated with the appearance of jumping behavior. On the 20th day after birth a dose-effect relationship was found for quinpirole HCl (0.10-3.0 mg/kg), with maximal jumping activity occurring between 30 and 150 min after the 3.0 mg/kg dose. On the 26th day after birth, both spiperone HCl (0.30 mg/kg i.p.) and SCH 23390 HCl (0.30 mg/kg i.p.) attenuated the quinpirole effect. At 34 days the jumping response was virtually absent. The age-related jumping behavior appears to be another manifestation of the abnormal responses meduated by supersensitized dopamine receptors in quinpirole-primed rats. Based on the ability of dopamine D1 and D2 receptor antagonists to attenuate this effect, quinpirole-induced jumping behavior may be a reflection of cooperativity of dopamine D1 and D2 receptor types.

Repeated postnatal treatment of rats with the dopamine receptor agonist, quinpirole results in exaggeration of selected behaviors that are induced by quinpirole in adulthood. To determine whether the antinociceptive response to quinpirole could be similarly enhanced, rats were treated daily from birth with quinpirole HCl (3.0 mg/kg per day i.p. × 28 days) and their response time in the hot plate analgesia test was determined at 4 months. An acute dose of quinpirole HCl (100 or 1000 μg/kg i.p.) produced an analgesic response in the neonatally primed rats and in the vehicle controls. More significantly, the effect was substantially greater in the quinpirole-primed group at each of these two doses of quinpirole. This effect of quinpirole was fully attenuated in both groups by treatment with the dopamine receptor antagonist, spiperone HCl (0.30 mg/kg i.p., 1 h before quinpirole). The analgesic effect of morphine sulfate (6.0 mg/kg i.p.) was not greater in the quinpirole-primed group. These findings demonstrate that the ontogenetic sensitization of quinpirole receptors results in enhanced antinociceptive responses to quinpirole in adulthood. This animal model may be useful for studying the involvement of dopamine systems in algesia and a analgesia.

Nicotine has been indicated as a prevalent drug for substance abuse comorbidities in mental illness. Tobacco use is elevated in those suffering from psychiatric disorders, most notably in schizophrenia (SZ), where a three-to-five fold increase in usage compared to the general population is observed. Our laboratory has established a rodent model of psychosis. In this model, male and female rats are neonatally treated with quinpirole (NQ), a dopamine (DA) D2-like agonist for 21 days postpartum, resulting in lifelong supersensitization of the DAD2 receptor. Increases in dopamine D2 receptor sensitivity is a hallmark of psychosis. Interestingly, the dopamine D2 receptor forms a triple mutual inhibitor heteromer in the dorsal striatum with the adenosine A(2A) and metabotropic glutamate receptor type 5 (mGlu5), such that stimulation of the A(2A) or mGlu5 receptor results in decreased dopamine D2 signaling. The present study was designed to analyze the role of the mGlu5 receptor in a behavioral task involved in testing the associative aspects of rewarding drugs known as conditioned place preference (CPP). CPP is a behavioral task in which animals are conditioned with a reinforcing drug to prefer a particular environmental context. Male and female rats were neonatally treated with saline (NS) or quinpirole from postnatal day (P) 1 to 21. From P41-51, which is mid-adolescence in a rat, all rats were behaviorally tested on CPP. Results revealed that compared to NS rats, NQ animals administered nicotine demonstrated enhanced CPP, replicating our past work. Groups receiving a positive allosteric modulator to mGlu5, which results in stimulation of the mGlu5 receptor, reduced the enhanced rewarding effects of nicotine in CPP for NQ treated rats equal to control levels. Brain tissue was analyzed for brain-derived neurotropic factor (BDNF), a neurotrophin involved in cell growth, as well cell adhesion molecule cadherin-13 in the ventral tegmental area (VTA), which is a brain area rich in dopamine cell bodies. Results revealed elevations of BDNF in NQ-treated rats given nicotine compared to all other groups, and a sex difference in the increase in cadherin-13, with female NQ rats given nicotine demonstrating increases compared to all other groups. These effects were blocked by the mGlu5 receptor positive allosteric modulator. In addition, we analyzed phospho-p70S6 kinase in the nucleus accumbens (NAcc), which is the dopamine neuronal terminal region in the VTA mitigating drug reward. The NQ group given nicotine demonstrated significant increases in NAcc P70S6 kinase compared to all other groups, suggesting increased synaptic growth, which was also blocked by the positive allosteric modulator to mGlu5. Taken together, these results elucidate mGlu5 as a drug target for reducing the rewarding effects of nicotine via CDPPB administration in a model of substance abuse in psychosis.