1.
Birgner, Carolina, 1978-
(author)
Anabolic androgenic steroids and central monoaminergic systems : Supratherapeutic doses of nandrolone decanoate affect dopamine and serotonin
2008
Doctoral thesis (other academic/artistic) abstract
Supratherapeutic doses of anabolic androgenic steroids (AASs) are administered, not only as performance-enhancing drugs in the world of sports, but also in order to modify behaviour. AAS abusers are at risk of developing serious physical and psychological side effects such as dependence and aggressive behaviour. The aim of this thesis was to investigate the impact of supratherapeutic doses of nandrolone decanoate after subchronic administration on dopamine and serotonin pathways involved in drug dependence and aggression, in the male rat brain.Adult male Sprague-Dawley rats received intramuscular injections of nandrolone decanoate (3 or 15 mg/kg) or vehicle once daily for 14 days. Nandrolone decanoate pre-exposure abolished the effect of amphetamine on the 3,4-dihydroxyphenylacetic acid (DOPAC) tissue level in the hypothalamus and on the DOPAC/dopamine ratio in the hypothalamus and the hippocampus. A significant decrease of the basal extracellular DOPAC and homovanillic acid (HVA) levels could be detected in the nucleus accumbens, which remained low during the first hour following the amphetamine challenge. Nandrolone decanoate significantly reduced the activity of both monoamine oxidase A and B (MAO-A and -B) in the caudate putamen and amygdala. The gene transcript levels of MAO-B, and the dopamine D1 and D4 receptors were altered in limbic regions. No changes in transcriptional levels could be detected among the serotonin receptor genes examined. However, the density of the serotonin transporter protein was elevated in a range of aggression-related brain regions.Taken together, subchronic administration of nandrolone decanoate causes dopaminergic and serotonergic dysregulations in distinct brain regions. These areas of the brain are involved in the development of drug dependence and expression of impulsive and aggressive behaviours. These results may contribute to explain some of the behavioural changes often reported in AAS abusers, such as polydrug use and impaired impulse control.
2.
Botros, Milad, 1951-
(author)
Characterization of Substance P (SP) Aminoterminal SP (1-7) Binding in Brain Regions and Spinal Cord of the Male Rat : Studies on the Interaction with Opioid Related Pathways
2008
Doctoral thesis (other academic/artistic) abstract
Binding sites for substance P(1-7), SP(1-7) have been identified and characterized for the first time in crude membrane fraction from rat CNS using tritiated ([3H]) SP(1-7) as tracer. These putative receptors were investigated in relation to their affinity for tachykinins, opioid peptides and sigma receptor ligands. [3H]-SP(1-7) specifically binds to high affinity binding sites identified as receptor targets for the heptapeptide SP (1-7). Two distinct binding sites were observed in the spinal cord. One site is recognized by high affinity for SP(1-7) with a Kd of 0.5 nM, whereas the other site showed low affinity for the heptapeptide (Kd=12 nM). In the brain, the binding of SP(1-7) fitted a single site binding model with a Kd of 4.4 nM and a Ki of 4.2 nM. Further, using the spinal cord membranes the binding of [3H]-SP (1-7) was weakly displaced by SP and other N-terminal fragments thereof and no or negligible affinity was observed for ligands of the NK-1, NK-2 and NK-3 tachykinin receptors, C-terminal SP(5-11), Tyr-w-MIF-1 or the mu-opioid receptor antagonists naloxone and naloxonazine. On the other hand it was significantly displaced by endomorphin-2, DAMGO, and Try-MIF-1 and exhibit some affinity for MIF-1, ß-casomorphin and endomorphin-1. However, only endomorphin-2, DAMGO and Tyr-MIF-1 showed affinity in the close range of the native peptide SP(1-7). The affinity of endomorphin-2 for the spinal cord site was 10 times lower than that of SP(1-7) but more than 100 times higher than the affinity recorded for endomorphin-1. Tyr-MIF-1 but not Tyr-w-MIF-1 showed similar affinity as endomorphin-2 for SP(1-7) site. All peptides exhibiting high affinity at the SP(1-7) site, have a phenylalanine or a leucine residue in their C-terminal structure.Further, synthetic analogues of SP(1-7) were tested for their affinity for the SP(1-7) receptor in the rat spinal cord. An important finding here was that the receptor-ligand-interaction was favoured by the C-terminal region of SP(1-7). Residues at positions 5-7 appeared crucial for binding to the specific SP(1-7) site. The presence of the amidated Phe7 residue was extremely critical for binding to the SP(1-7) site.The analogue Gln5-Gln6-Phe7-NH2 was almost equipotent with the parent peptide in the SP (1-7) receptor binding assay.Furthermore, the SP(1-7)-amide potently and dose dependently reduced several signs of the reaction to morphine withdrawal and was significantly attenuated by the addition of the sigma agonist SK-10047.In conclusion, the work presented in this thesis has contributed the characterization of the properties of highly selective binding sites for SP(1-7) in the rat spinal cord and VTA. These sites appear to be distinct from the µ-opioid receptor or any of the known neurokinin receptors. The study further indicates that the SP(1-7)-amide mimics the effect of the nativ heptapeptide and that the mechanisms for its action involve a sigma receptor site.
3.
Hallberg, Mathias, 1971-
(author)
Anabolic Androgenic Steroids : Effects on Neuropeptide Systems in the Rat Brain
2005
Doctoral thesis (other academic/artistic) abstract
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.
4.
Karlsson, Krister, 1972-
(author)
Substance P Endopeptidase : Purification and Characterizataion of Enzyme Activity and Evaluation of its Function during Stressful Condition
2004
Doctoral thesis (other academic/artistic) abstract
The purification and biochemical characterization of the substance P (SP) hydrolyzing enzyme, substance P endopeptidase (SPE), have been carried out; with subsequent orientation in neurobiological fundamental processes involved in opioid dependence, withdrawal, and heat-stress.SPE was purified from rat spinal cord, human spinal cord and cerebrospinal fluid (CSF), rat ventral tegemental area (VTA), and rat hippocampus. The enzyme activity was found to release the biologically active fragments SP(1-7) and SP(1-8) as major products. The purified enzymes were characterized with regard to their biochemical and kinetic properties. The typical SPE is neither inhibited by phosphoramidon nor captopril nor phenylmethanesulfonylflourid (PMSF). In comparison to other known proteases SPE differed in characteristics regarding substrate specificity, inhibition-profile, cleavage pattern, and other kinetic parameters. The technically very delicate approach of micro purification of SPE from the rat ventral tegemental area (VTA) (this is a very small tissue), turned out to be possible with the ÄKTA™-purifier system. Studies revealed a crucial role of SPE in a series of clinically important neuropathological conditions, such as opioid tolerance, and withdrawal (SPE, increased); and heat-stress (SPE, increased). These findings emerged from assessment of enzyme activity in hypothalamus, nucleus accumbens (NAc) periaqueductal gray (PAG), pituitary, striatum, substantia nigra (SN), VTA, spinal cord. Viewing the role of SPE in morphine tolerance, it was possible to note regional differences with a decrease in PAG, and striatum, whereas an increase was seen in SN, and VTA. After heat-stress treatment, SPE was raised in several regions (cerebral cortex, hippocampus, diencephalon, cerebellum, spinal cord), and the most precise observation of this was located to the hippocampus structure.
5.
LaForge, Karl Steven, 1957-
(author)
Preproenkephalin Gene and mRNA : Studies of Structure, Function, Cocaine Responses in an Animal Model, and Genetic Association with Human Opiate Addiction
2004
Doctoral thesis (other academic/artistic) abstract
The endogenous opioid enkephalin neuropeptides are mediators of pain perception and have been implicated in human addictions. The preproenkephalin gene and its mRNA have also provided many examples of tissue- and species-specific variations in mRNA structure produced through a variety of transcriptional and post-transcriptional mechanisms. Resultant differences in mRNA structure, in several cases, have impact on translation of enkephalin prepropeptide. The reports and discussion presented herein describe studies of the preproenkephalin gene and mRNA structure in the guinea pig, an animal that may have specific advantages for modeling the human endogenous opioid system. A guinea pig brain cDNA library was constructed and screened for clones of preproenkephalin and preprodynorphin, which were then sequenced. These studies confirmed the predicted mRNA structure that had been previously proposed based on homology with gene sequences and other methods. Multiple transcription initiation sites for each of these prepropeptide genes were also identified. Studies were conducted in the guinea pig to evaluate the effects of the administration of cocaine in a “binge” paradigm for two and seven days on preproenkephalin mRNA levels in several brain regions. “Binge” cocaine administration for seven (but not two) days resulted in differential changes in mRNA levels in different brain regions. Decreases were observed in the nucleus accumbens and hypothalamus, and increases in the frontal cortex, amygdala and hippocampus. These findings differ from those of previous rodent studies and suggest that this species may provide a useful alternative model for the study of the effects of cocaine on preproenkephalin gene expression in the human brain. Human genetic studies were also conducted in opioid-dependent (formerly heroin-addicted) and control subjects to test the hypothesis that the preproenkephalin gene is associated with heroin addiction. In two separate studies, we obtained evidence that this gene may be associated with the development of human heroin addiction.
6.
Le Grevès, Madeleine, 1966-
(author)
CNS Targets for GH and IGF-1 : Emphasis on Their Regulation in Relation to Cognitive Processes
2005
Doctoral thesis (other academic/artistic) abstract
The interest for the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and its role in the central nervous system (CNS) has grown during the past decade. GH has been associated with psychological functions as sleep, mood, general well-being and learning and memory. The present thesis is a contribution to clarify the functions and mechanisms involved in the actions of GH and IGF-1 in the CNS. A variant of the GH receptor (GHR) gene transcript lacking exon 3 (GHR3-) was cloned from ovine choroid plexus epithelial cells and tissue. The GHR3- transcript has previously only been identified in human tissue. Further, an anatomical study of the localization of GHR mRNA in the rat brain stem and spinal cord was carried out by the use of in situ hybridization. High densities of GHRs were found in areas associated with the regulation of food intake, sleep and nociception, functions known to be influenced by the GH/IGF-1 axis. The interaction with the opioid system was studied by an acute treatment with morphine. The levels of the transcripts for GHR and GHBP in the rat hippocampus and spinal cord were decreased 4 h after the injection of the opiate and restored to normal levels after 24 h. Young and aged rats injected with GH or IGF-1 showed differential gene regulation of subunits of the NMDA subtype of glutamate receptor in the hippocampus. This indicates an age-related difference in the sensitivity to GH/IGF-1 mediated effects on memory functions. Moreover, hypophysectomized rats treated with GH showed improved performance in the Morris water maze, a spatial memory task. The effect was accompanied with an increase in transcripts for NMDA receptor subunits and its associated membrane anchoring PSD-95 protein. Taken together, the results suggest that GH and/or IGF-1 play important roles in mechanisms associated with cognitive functions.
7.
Magnusson, Kristina, 1976-
(author)
The Impact of Nandrolone Decanoate on Neuropeptidergic Mechanisms Related to Cognition, Aggression, Reward and Dependence
2009
Doctoral thesis (other academic/artistic) abstract
The abuse of anabolic androgenic steroids (AAS) is becoming increasingly common and may result in a range of physiological as well as psychological effects such as altered behavior in terms of increased aggression, cognitive dysfunction and addictive behavior. AAS comprise testosterone and its derivatives, of which nandrolone is one of the more common. Previous studies have shown nandrolone-induced effects in male rats on peptide levels within the Substance P (SP) system and the dynorphinergic system; these effects may be linked to some of the reported behavior alterations. The studies presented in this thesis aimed to investigate the mechanisms underlying these peptide alterations and also to further investigate neuropeptidergic effects attributed to nandrolone administration. The results display significant effects on the enzymatic conversion of SP and Dynorphin A into their bioactive metabolites SP(1-7) and Leu-enkephalin-Arg6, respectively, as a result of nandrolone treatment. More profound investigations on the dynorphinergic system displayed effects on the kappa opioid receptor density in various brain regions. There was also a significant increase in the expression of the gene transcript of prodynorphin in the hippocampus, a brain region associated with cognitive processes. In addition, impaired spatial learning and memory in the Morris water maze task following nandrolone administration was encountered. The results provide further understanding regarding neuropeptidergic mechanisms underlying AAS-induced behavioral effects.
