The mechanisms that mediate the maintenance of chronic pain states are poorly understood, but elucidation of such could yield insight into how pain becomes chronic and how the process can potentially be reversed. This thesis investigated the role of ascending and descending spinal dorsal horn circuitry and interneurons in the plasticity that mediates a transition to pathological pain plasticity using hyperalgesic priming model. The results showed that, while dorsal horn neurokinin 1 receptor-positive neurons or descending serotonergic neurons mediated IL-6- and carrageenan-induced acute mechanical hypersensitivity, they were not required for PGE₂-induced mechanical hypersensitivity. In stark contrast, ablation of dopaminergic neurons did interrupt the IL-6- and carrageenan-induced mechanical hypersensitivity, but the subsequent PGE₂ injection failed to cause mechanical hypersensitivity - thereby reflecting that primed state plasticity is driven by differential mechanisms. In addition, the pharmacological antagonism of spinal dopamine D1/D5 receptors reversed priming and its agonism induced mechanical hypersensitivity exclusively in primed mice, which suggests dopaminergic control of pathological pain plasticity in a D1/D5-dependent manner. Moreover, in a primed state, changes to spinal dorsal horn GABA pharmacology were accompanied by upregulation of neuroligin 2 mRNA and protein expression. These findings 1) indicate a novel role for descending dopaminergic neurons in the maintenance of pathological pain plasticity, and 2) point to the inhibitory synaptic expression of neuroligin-2 as the spinal determinants of this type of pain plasticity.

La sécrétion d'aldostérone par la glande surrénale est principalement contrôlée par le système rénine-angiotensine circulant (SRA) et la kaliémie. La synthèse de l'aldostérone est également influencée par les facteurs paracrines intra-surrénaliens, y compris les neuropeptides. En particulier, les tachykinines, comme la substance P (SP), peuvent être libérées par les terminaisons nerveuses dans le cortex surrénalien. Le rôle de la SP dans la régulation de la fonction surrénalienne a été évalué chez l'animal mais rarement étudié chez l'homme. Le but de la présente étude est d'explorer le rôle de la SP dans le contrôle de la synthèse des minéralocorticoïdes dans la glande surrénale humaine. Des expériences in vitro conduites dans des échantillons surrénaliens normaux révèlent l'expression de SP codée par TAC1 qui est détecté par immunohistochimie dans des fibres nerveuses non-adrénergiques non-cholinergiques dans la zone glomérulée. Les fibres SP-positives établissent des contacts étroits avec des cellules productrices d'aldostérone qui expriment le récepteur NK1 (NK1R), récepteur de la SP. La SP stimule la production d'aldostérone à partir de cellules corticosurrénales cultivées, un effet qui est inhibé par l'aprépitant, antagoniste NK1R. L'action de la SP est relayée par la voie ERK et implique une régulation à la hausse de plusieurs gènes codant pour des enzymes de la stéroïdogénèse. Le rôle physiologique de la SP dans la régulation de la sécrétion d'aldostérone a été évalué à l'aide d'un essai clinique prospectif, contrôlé par placebo, de l'impact de l'aprépitant sur les concentrations plasmatiques et urinaires d'aldostérone chez des volontaires sains. L'aprépitant a réduit la production quotidienne d'aldostérone et la concentration plasmatique d'aldostérone (CPA) dans le décubitus, mais n'a pas modifié les CPA en position debout. Ces données montrent que la SP exerce un tonus stimulant sur la production d'aldostérone chez l'homme. / Aldosterone secretion by the adrenal gland is principally under control of the circulating renin-angiotensin system (RAS) and kalemia. Aldosterone synthesis is also influenced by intra-adrenal paracrine factors including neuropeptides. Especially, tachykinins, like substance P (SP), can be released by nerve endings in the adrenal cortex. The role of SP in the regulation of the adrenal function has been evaluated in animals but only scarcely investigated in humans. The aim of the present study is to explore the role of SP in the control of mineralocorticoid synthesis in the human adrenal gland. In vitro experiments conducted in normal adrenal samples reveal expression of the TAC1 encoding SP which is detected by immunohistochemistry in non adrenergic non cholinergic nerve fibres in the zona glomerulosa. SP-positive fibres establish close contacts with aldosterone-producing cells which express the SP receptor, i.e. the NK1 receptor (NK1R). SP stimulates aldosterone production from cultured adrenocortical cells, an effect which is inhibited by the NK1R antagonist aprepitant. The action of SP is mediated by the ERK pathway and involves upregulation of several genes encoding steroidogenic enzymes. The physiological role of SP in the regulation of aldosterone secretion was further assessed through a prospective clinical placebo-controlled trial investigating the impact of aprepitant on plasma and urine aldosterone levels in healthy volunteers. Aprepitant reduced daily aldosterone production and plasma aldosterone concentration (PAC) in recumbency but did not modify PAC in upright position. These data show that SP exerts a stimulatory tone on aldosterone production in man.

Cough in lung cancer (LC) is a significant unmet need. There are no evidence-based effective antitussives for its treatment and a lack of well-designed trials incorporating validated cough assessment tools and placebo controls. There is little research on its underlying mechanisms, perhaps with the assumption that it is simply 'due to the cancer'. Therefore, we have sought to characterise cough in terms of its severity, impact on quality of life, frequency and prevalence using LC specific subjective and objective assessment tools for the first time. We have also explored its potential mechanisms and treatment. Published preclinical data show that the substance P/neurokinin-1(NK1) pathway is implicated in cough in 5 different species. This pathway is targeted by the antiemetic aprepitant in humans. Data on the use of aprepitant as a novel antitussive are presented. To characterise cough and assess cough assessment tools in a cohort of patients with LC attending outpatient clinics, subjective and objective cough assessment tools including 24-hour ambulatory cough monitoring (ACM), were used to determine the cough severity, frequency, impact and cough- associated clinical factors in a longitudinal study. To determine cough prevalence, a cross sectional study of all patients attending thoracic oncology outpatient clinics in a single centre over a defined period were approached to determine whether they had a cough, to provide demographic and cancer related data and if applicable, to complete the Manchester Cough in Lung Cancer Scale (MCLCS) cough impact questionnaire and the cough severity visual analogue scale. To explore the role of the NK1 pathway in cough in patients with LC, a single-arm randomised placebo controlled pilot trial assessing aprepitant for the treatment of cough was conducted. The presented data demonstrated that cough affects over half of patients with LC, representing a huge unmet clinical need. Over 2/3rds of patients felt that their cough was severe enough to warrant treatment and over 1/4 described it as painful. Patients with LC suffer from a very severe and frequent cough. Its impact is considerable, with effects on physical, psychological and social domains. The longitudinal study is the first to report that cough severity and impact is predicted by gastro-intestinal co-morbidities rather than cancer related factors. The presented data demonstrate that ACM is feasible and acceptable to patients with LC. This provides researchers with an objective endpoint for use in clinical trials. The MCLCS performs well and is valid. The cough intervention trial is the first to demonstrate that aprepitant is associated with lower subjective cough scores and cough frequency using validated cough assessment tools. No antitussive therapy study has ever shown a positive antitussive effect using both types of cough assessment tools in the LC population. This suggests that the substance P/NK1 pathway is implicated in cough in LC and identifies this as a potential new therapeutic target, providing exciting data and hope for future patients with LC.

Hepatocyte growth factor (HGF) and its specific receptor MET play a role in many physiological functions including proliferation, migration and morphogenesis. Recently, research results in our laboratory showed that recombinant HGF variants (NK1, NK2, NK3 and NK4) became antagonists to HGF/MET pathway by suppressing proliferation, migration and invasion in human breast cancer cells (MDA-MB-435S, MDA). Similar results were achieved when HGF variants genes were introduced in MDA cells. To understand the molecular mechanism of breast cancer cells metastasis suppressed by HGF variants, MDA and five transfectants, including MDA-GFP, MDA-NK1, MDA-NK2, MDA-NK3 and MDA-NK4 cells were used for proteomic analysis using two-dimensional electrophoresis (2-DE). Differential analysis revealed that a total of 56 polypeptides were differentially expressed through five sets of comparison using wild-type MDA cells as a control. A total of 17 polypeptides were shown differential expression between MDA and MDA-GFP cells, with 11 down-regulated and 6 up-regulated. Eighteen polypeptides were differentially expressed between MDA and MDA-NK1 cells, with 15 down-regulated and 3 up-regulated. There were 22 differentially expressed polypeptides found between MDA and MDA-NK2 cells, in which 14 were down-regulated and 8 were up-regulated. Sixteen polypeptides were shown differentially expressed between MDA and MDA-NK3 cells, with 11 down-regulated and 5 up-regulated. A total of 18 polypeptides were shown differential expression between MDA and MDA-NK4 cells, with 15 down-regulated and 3 up-regulated. Proteomic analysis showed that a total of 43 polypeptides were differentially expressed through four sets of comparison (MDA-GFP and MDA-NK1, MDA-GFP and MDA-NK2, MDA-GFP and MDA-NK3, and MDA-GFP and MDA-NK4). To understand the differential expression among different HGF variants-transfected MDA cells, three sets of cross analysis were also carried out (MDA-NK1 and MDA-NK2, MDA-NK1 and MDA-NK3, and MDA-NK1 and MDA-NK4) and the results showed that a total of 37 differentially expressed polypeptides were found in the three sets of comparison. Similarly, when MDA-NK2 cells were used as a control to compare with MDA-NK3 and MDA-NK4 cells, 34 significantly differential expressed polypeptides were found. The last set of comparison between MDA-NK3 and MDA-NK4 cells, 19 polypeptides were found significantly differential expression. Therefore, our current results revealed that the differentially expressed polypeptides in MDA-MB-435S cells and HGF variants-transfected MDA cells could be related to the inhibition of proliferation and migration of human breast cancer cells by HGF variants.

Nous avons étudié les relations anatomiques entre les systèmes de neurotransmission à substance P (SP) et à sérotonine (5-hydroxytryptamine, 5-HT) dans le noyau du raphé dorsal (NRD) du rongeur, afin de mieux comprendre les interactions entre ces systèmes durant la régulation de l’humeur. Le NRD reçoit une innervation SP provenant de l’habenula, et le blocage pharmacologique des récepteurs neurokinine-1 (rNK1) de la SP aurait des effets antidépresseurs. Chez le rongeur, le traitement par les antagonistes des rNK1 s’accompagne d’une désensibilisation des autorécepteurs 5-HT1A de la 5-HT et d’une hausse de l’activité des neurones 5-HT dans le NRD, suggérant des interactions locales entre ces deux systèmes. Dans un premier temps, nous avons démontré par doubles marquages immunocytochimiques en microscopies optique, confocale et électronique, la présence du rNK1 dans une sous-population de neurones 5-HT du NRD caudal. Lors de l’analyse en microscopie électronique, nous avons pu constater que les rNK1 étaient principalement cytoplasmiques dans les neurones 5-HT et membranaires sur les neurones non 5-HT du noyau. Grâce à d’autres doubles marquages, nous avons aussi pu identifier les neurones non-5-HT porteurs de rNK1 comme étant GABAergiques. Nous avons ensuite combiné l’immunomarquage de la SP avec celui du rNK1, dans le but d’examiner les relations entre les terminaisons (varicosités *) axonales SP et les neurones 5-HT (pourvus de rNK1 cytoplasmiques du NRD caudal. En simple marquage de la SP, nous avons pu estimer à 41% la fréquence avec laquelle les terminaisons SP font synapse. Dans le matériel doublement marqué pour la SP et son récepteur, les terminaisons SP ont été fréquemment retrouvées en contact direct ou à proximité des dendrites munies de rNK1 cytoplasmiques, mais toujours éloignées des dendrites à rNK1 membranaires. Pour tester l’hypothèse d’une internalisation soutenue des rNK1 par la SP dans les neurones 5-HT, nous avons ensuite examiné la localisation subcellulaire du récepteur chez le rat traité avec un antagoniste du rNK1, le RP67580. La densité du marquage des rNK1 a été mesurée dans le cytoplasme et sur la membrane des deux types de dendrites (5-HT: rNK1 cytoplasmiques; non 5-HT: rNK1 membranaires). Une heure après une injection unique de l’antagoniste, la distribution du rNK1 est apparue inchangée dans les deux types de neurones (5-HT et non 5-HT). Par contre, après un traitement quotidien de 7 ou 21 jours avec l’antagoniste, nous avons mesuré une augmentation significative des densités cytoplasmique et membranaire du rNK1 dans les neurones 5-HT, sans aucun changement dans les neurones non 5-HT. Ces traitements ont aussi augmenté l’expression du gène rNK1 dans le NRD. Enfin, nous avons mesuré une hausse de la densité membranaire du rNK1 dans les neurones 5-HT, sans hausse de densité cytoplasmique, par suite d’une lésion bilatérale de l’habenula. Ces résultats confortent l’hypothèse d’une activation et d’une internalisation soutenues des rNK1 par la SP dans les neurones 5-HT du NRD caudal. Ils suggèrent aussi que le trafic des rNK1 dans les neurones 5-HT du NRD représente un mécanisme cellulaire en contrôle de l’activation du système 5-HT par les afférences SP en provenance de l’habenula. / We have studied in detail the relationships between substance P (SP) and serotonin (5-hydroxytryptamine, 5-HT) neurotransmission systems in the dorsal raphe nucleus (DRN) of rodents, in order to further our understanding of their interaction during mood regulation. The DRN receives a SP innervation arising from the habenula and, in human, it is known that blockade of the neurokinin-1 receptor (NK1r) of SP by antagonists may have antidepressant effects. In rodents, treatment with NK1r antagonists is known to increase the firing of DRN 5-HT neurons and to induce a desensitization of their 5-HT1A autoreceptors, suggesting local interactions between the SP and 5-HT systems. In a first step, we were able to demonstrate by means of light, confocal, and electron microscopic immunocytochemistry, including double immunolabelings of NK1r and of the biosynthetic enzyme of 5-HT, tryptophane hydroxylase, the presence of NK1r in a subpopulation of 5-HT neurons in the caudal DRN of rat and mouse. After the dual immunolabelings for electron microscopy, we also found that NK1r was mostly cytoplasmic in 5-HT neurons while predominating on the plasma membrane of TPH negative (non 5-HT) neurons. Subsequently, in additionnal double labeling experiments, we were able to identify most if not all non 5-HT dendrites bearing membranous NK1r as GABAergic. In a second step, we combined the immunolabeling of SP with that of NK1r, in order to examine the relationships between SP axon terminals (varicosities *) and the two categories of DRN neurons (5-HT: cytoplasmic NK1r; non 5-HT: membranous NK1r). After single SP labeling, we could estimate the frequency with which SP terminals made synapse at 41%, at least. In the material doubly labeled for SP and NK1r, the SP terminals were often found in close contact or in the immediate proximity of dendrites endowed with cytoplasmic receptor, but never near non 5-HT dendrites bearing membrane bound receptors. To test the hypothesis of a sustained internalization of NK1r in 5-HT neurons, we then tested the effects of RP67580, a selective NK1r antagonist, on the subcellular localization of the receptor. One hour after administration of a single dose, the NK1r distribution was unchanged in both types of dendrites (5-HT and non 5-HT). However, after administration for 7 (subchronic) or 21 (chronic) days, the cytoplasmic and the membrane densities of NK1r were significantly increased in 5-HT dendrites, without any change in non 5-HT dendrites. These treatments also increased NK1r gene expression in the caudal DRN. Lastly, a significant increase in the membrane density of NK1r was measured in the 5-HT neurons, without any increase of the cytoplamic density, following bilateral electrolytic lesioning of the habenula. These results strenghtened the hypothesis of a sustained activation and internalization of NK1r by SP in 5-HT neurons of the caudal DRN. They also suggested that trafficking of NK1r in these cells might represent a cellular mechanism in control of the activation of the 5-HT system by SP afferents from the habebula.

Nous avons étudié les relations anatomiques entre les systèmes de neurotransmission à substance P (SP) et à sérotonine (5-hydroxytryptamine, 5-HT) dans le noyau du raphé dorsal (NRD) du rongeur, afin de mieux comprendre les interactions entre ces systèmes durant la régulation de l’humeur. Le NRD reçoit une innervation SP provenant de l’habenula, et le blocage pharmacologique des récepteurs neurokinine-1 (rNK1) de la SP aurait des effets antidépresseurs. Chez le rongeur, le traitement par les antagonistes des rNK1 s’accompagne d’une désensibilisation des autorécepteurs 5-HT1A de la 5-HT et d’une hausse de l’activité des neurones 5-HT dans le NRD, suggérant des interactions locales entre ces deux systèmes. Dans un premier temps, nous avons démontré par doubles marquages immunocytochimiques en microscopies optique, confocale et électronique, la présence du rNK1 dans une sous-population de neurones 5-HT du NRD caudal. Lors de l’analyse en microscopie électronique, nous avons pu constater que les rNK1 étaient principalement cytoplasmiques dans les neurones 5-HT et membranaires sur les neurones non 5-HT du noyau. Grâce à d’autres doubles marquages, nous avons aussi pu identifier les neurones non-5-HT porteurs de rNK1 comme étant GABAergiques. Nous avons ensuite combiné l’immunomarquage de la SP avec celui du rNK1, dans le but d’examiner les relations entre les terminaisons (varicosités *) axonales SP et les neurones 5-HT (pourvus de rNK1 cytoplasmiques du NRD caudal. En simple marquage de la SP, nous avons pu estimer à 41% la fréquence avec laquelle les terminaisons SP font synapse. Dans le matériel doublement marqué pour la SP et son récepteur, les terminaisons SP ont été fréquemment retrouvées en contact direct ou à proximité des dendrites munies de rNK1 cytoplasmiques, mais toujours éloignées des dendrites à rNK1 membranaires. Pour tester l’hypothèse d’une internalisation soutenue des rNK1 par la SP dans les neurones 5-HT, nous avons ensuite examiné la localisation subcellulaire du récepteur chez le rat traité avec un antagoniste du rNK1, le RP67580. La densité du marquage des rNK1 a été mesurée dans le cytoplasme et sur la membrane des deux types de dendrites (5-HT: rNK1 cytoplasmiques; non 5-HT: rNK1 membranaires). Une heure après une injection unique de l’antagoniste, la distribution du rNK1 est apparue inchangée dans les deux types de neurones (5-HT et non 5-HT). Par contre, après un traitement quotidien de 7 ou 21 jours avec l’antagoniste, nous avons mesuré une augmentation significative des densités cytoplasmique et membranaire du rNK1 dans les neurones 5-HT, sans aucun changement dans les neurones non 5-HT. Ces traitements ont aussi augmenté l’expression du gène rNK1 dans le NRD. Enfin, nous avons mesuré une hausse de la densité membranaire du rNK1 dans les neurones 5-HT, sans hausse de densité cytoplasmique, par suite d’une lésion bilatérale de l’habenula. Ces résultats confortent l’hypothèse d’une activation et d’une internalisation soutenues des rNK1 par la SP dans les neurones 5-HT du NRD caudal. Ils suggèrent aussi que le trafic des rNK1 dans les neurones 5-HT du NRD représente un mécanisme cellulaire en contrôle de l’activation du système 5-HT par les afférences SP en provenance de l’habenula. / We have studied in detail the relationships between substance P (SP) and serotonin (5-hydroxytryptamine, 5-HT) neurotransmission systems in the dorsal raphe nucleus (DRN) of rodents, in order to further our understanding of their interaction during mood regulation. The DRN receives a SP innervation arising from the habenula and, in human, it is known that blockade of the neurokinin-1 receptor (NK1r) of SP by antagonists may have antidepressant effects. In rodents, treatment with NK1r antagonists is known to increase the firing of DRN 5-HT neurons and to induce a desensitization of their 5-HT1A autoreceptors, suggesting local interactions between the SP and 5-HT systems. In a first step, we were able to demonstrate by means of light, confocal, and electron microscopic immunocytochemistry, including double immunolabelings of NK1r and of the biosynthetic enzyme of 5-HT, tryptophane hydroxylase, the presence of NK1r in a subpopulation of 5-HT neurons in the caudal DRN of rat and mouse. After the dual immunolabelings for electron microscopy, we also found that NK1r was mostly cytoplasmic in 5-HT neurons while predominating on the plasma membrane of TPH negative (non 5-HT) neurons. Subsequently, in additionnal double labeling experiments, we were able to identify most if not all non 5-HT dendrites bearing membranous NK1r as GABAergic. In a second step, we combined the immunolabeling of SP with that of NK1r, in order to examine the relationships between SP axon terminals (varicosities *) and the two categories of DRN neurons (5-HT: cytoplasmic NK1r; non 5-HT: membranous NK1r). After single SP labeling, we could estimate the frequency with which SP terminals made synapse at 41%, at least. In the material doubly labeled for SP and NK1r, the SP terminals were often found in close contact or in the immediate proximity of dendrites endowed with cytoplasmic receptor, but never near non 5-HT dendrites bearing membrane bound receptors. To test the hypothesis of a sustained internalization of NK1r in 5-HT neurons, we then tested the effects of RP67580, a selective NK1r antagonist, on the subcellular localization of the receptor. One hour after administration of a single dose, the NK1r distribution was unchanged in both types of dendrites (5-HT and non 5-HT). However, after administration for 7 (subchronic) or 21 (chronic) days, the cytoplasmic and the membrane densities of NK1r were significantly increased in 5-HT dendrites, without any change in non 5-HT dendrites. These treatments also increased NK1r gene expression in the caudal DRN. Lastly, a significant increase in the membrane density of NK1r was measured in the 5-HT neurons, without any increase of the cytoplamic density, following bilateral electrolytic lesioning of the habenula. These results strenghtened the hypothesis of a sustained activation and internalization of NK1r by SP in 5-HT neurons of the caudal DRN. They also suggested that trafficking of NK1r in these cells might represent a cellular mechanism in control of the activation of the 5-HT system by SP afferents from the habebula.

Epilepsy is a common neurological disease affecting 6 million people in Europe. Early prevention and accurate diagnosis and treatment are of importance to obtain seizure freedom. In this thesis new applications of carbon-11-labelled tracers in PET and autoradiographic studies were explored in focal epilepsy. Patients with low-grade gliomas often experience epileptic seizures. A retrospective PET-study assessing seizure activity, metabolic rate measured with 11C-methionine and other known prognostic factors was performed in patients with glioma. No correlation was found between seizure activity and uptake of methionine. The presence and termination of early seizures was a favourable prognostic factor. Activation of the neurokinin-1 (NK1) receptor by substance P (SP) induces epileptic activity. PET with the NK1 receptor antagonist GR205171 was performed in patients with temporal lobe epilepsy (TLE) and healthy controls. In TLE patients an increased NK1 receptor availability was found in both hemispheres, most pronounced in anterior cingulate gyrus ipsilateral to seizure onset. A positive correlation between NK1 receptors and seizure frequency was observed in ipsilateral medial structures consistent with an intrinsic network using the NK1-SP receptor system for transmission of seizure activity. The uptake of 18F-fluoro-deoxy-glucose (FDG) is related to cerebral blood flow (CBF). Previously, methods to estimate blood flow from dynamic PET data have been described. A retrospective study was conducted in 15 patients undergoing epilepsy surgery investigation, including PET with 11C-FDG and 11C-Flumazenil (FMZ). The dynamic FMZ dataset and pharmacokinetic modeling with a multilinear reference tissue model were used to determine images of relative CBF. Agreement between data of FDG and CBF was analyzed showing a close association between interictal brain metabolism and relative CBF. Epilepsy often occurs after traumatic brain injuries. Changes in glia and inhibitory neuronal cells contribute to the chain of events leading to seizures. Autoradiography with 11C-PK11195, 11C-L-deprenyl and 11C-Flumazenil in an animal model of posttraumatic epilepsy studied the temporal and spatial distribution of microglia, astrocytes and GABAergic neurons. Results showed an instant increase in microglial activity that subsequently normalized, a late formation of astrogliosis and an instant and prolonged decease in GABA binding. The model can be used to visualize pathophysiological events during the epileptogenesis.

<p>Anabolic-androgenic steroids (AAS) have been used in clinics for decades. The misuse of AAS has previously been attributed merely to sport athletes, taking AAS with intentions to increase muscle mass, enhance physical performance and to improve results in competitions. Today, the misuse of AAS has spread to adolescents and young adults not connected to sports. Alarmingly, many reports are pointing at severe psychiatric adverse effects among AAS abusers, which include mood swings, mania, anxiety, depression and aggression. Numerous examples of severe and often unprovoked violence and brutal crimes have been connected to AAS abuse and there is a strong need for a better understanding of the underlying biochemical events that might account for the adverse behaviors induced by AAS. The general aim of this thesis was to study the effect of chronic AAS administration on neuropeptide circuits in the rat brain associated with the regulation of rewarding effects, memory, anxiety, depression and aggression, using nandrolone decanoate as a prototype AAS.</p><p>Results demonstrated that daily administration of AAS to rats in doses comparable to those taken by AAS abusers, in certain brain structures significantly affected, <i>a</i>) the levels of the opioid peptides dynorphin B and Met-enkephalin-Arg⁶Phe⁷, <i>b</i>) the levels of the tachykinin substance P (SP), <i>c</i>) the density of the SP neurokinin 1 (NK1) receptor, <i>d</i>) the level of the SP metabolite SP_1-7that frequently exerts opposite effects to SP, <i>e</i>) the SP_1-7generating enzyme substance P endopeptidase (SPE) and finally, <i>f</i>) the levels of the neuropeptide calcitonin gene-related peptide (CGRP) often co-localized with SP. The alterations seen in the levels and activities of these neurochemical components are in many aspects compatible with behaviors typified among AAS abusers.</p>

Anabolic-androgenic steroids (AAS) have been used in clinics for decades. The misuse of AAS has previously been attributed merely to sport athletes, taking AAS with intentions to increase muscle mass, enhance physical performance and to improve results in competitions. Today, the misuse of AAS has spread to adolescents and young adults not connected to sports. Alarmingly, many reports are pointing at severe psychiatric adverse effects among AAS abusers, which include mood swings, mania, anxiety, depression and aggression. Numerous examples of severe and often unprovoked violence and brutal crimes have been connected to AAS abuse and there is a strong need for a better understanding of the underlying biochemical events that might account for the adverse behaviors induced by AAS. The general aim of this thesis was to study the effect of chronic AAS administration on neuropeptide circuits in the rat brain associated with the regulation of rewarding effects, memory, anxiety, depression and aggression, using nandrolone decanoate as a prototype AAS. Results demonstrated that daily administration of AAS to rats in doses comparable to those taken by AAS abusers, in certain brain structures significantly affected, a) the levels of the opioid peptides dynorphin B and Met-enkephalin-Arg6Phe7, b) the levels of the tachykinin substance P (SP), c) the density of the SP neurokinin 1 (NK1) receptor, d) the level of the SP metabolite SP1-7 that frequently exerts opposite effects to SP, e) the SP1-7 generating enzyme substance P endopeptidase (SPE) and finally, f) the levels of the neuropeptide calcitonin gene-related peptide (CGRP) often co-localized with SP. The alterations seen in the levels and activities of these neurochemical components are in many aspects compatible with behaviors typified among AAS abusers.

Anxiety disorders are very common and the primary feature is abnormal or inappropriate anxiety. Fear and anxiety is often mediated by the amygdala, a brain structure rich in substance P (SP) and neurokinin 1 (NK1) receptors. To learn more about how the human amygdala is modulated by fear and anxiety in event-triggered anxiety disorders and to investigate if the SP/NK1 receptor system is affected, regional cerebral blood flow (rCBF) ([15O]-water; Study I and II) and the SP/NK1 receptor system ([11C]GR205171; Study III and IV) were studied with positron emission tomography (PET). In Study I we investigated the neural correlates of affective startle modulation in persons with specific phobia by measuring rCBF during exposure to fearful and non-fearful pictures, paired and unpaired with acoustic startle stimuli. Fear-potentiated startle was associated with activation of the affective part of the anterior cingulate cortex and the left amygdaloid–hippocampal area. In Study II short-term drug treatment effects on rCBF in patients diagnosed with social phobia was evaluated, comparing the NK1 receptor antagonist GR205171 to the selective serotonin reuptake inhibitor citalopram and placebo. Social anxiety and neural activity in the medial temporal lobe including the amygdala was significantly reduced by both drugs but not placebo. In Study III we investigated if activity in the SP/NK1 receptor system in the amygdala would be affected by fear provocation in individuals with specific snake or spider phobia. Fear provocation was associated with a decreased uptake of the NK1 antagonist [11C]GR205171 in the amygdala, possibly explained by an increase in endogenous SP release occupying the NK1 receptors. Study IV was conducted to explore the resting state NK1 receptor availability in PTSD patients as compared to healthy controls. Increased resting state binding of the tracer [11C]GR205171 in the amygdala of patients with PTSD suggested an increased amount of available receptors. In summary, fear and fear-potentiated startle modulates the human amygdala, possibly through the SP/NK1 receptor system.