Electroconvulsive therapy (ECT) effectively treats depression by administration of repeated seizure-inducing electrical stimuli. Sprague-Dawley rats were administered 6 electroconvulsive shocks (ECS) over 2 weeks, and in vivo single unit extracellular electrophysiological activity was recorded after 48 hours. Overall firing activity in the locus coeruleus and ventral tegmental area was unchanged, suggesting the therapeutic efficacy of ECT may not be attributed to increased norepinephrine and dopamine release. There were more spontaneously active neurons in the substantia nigra pars compacta (SNc), indicating greater dopamine tone in the nigrostriatal motor pathway, which may contribute to alleviation of psychomotor retardation. In the facial motor nucleus (FMN), locally administered norepinephrine, but not serotonin, facilitated greater glutamate-induced firing, which may contribute to improved facial motricity. Current results indicate that repeated ECS enhances postsynaptic norepinephrine neurotransmission in the FMN and SNc dopamine neurotransmission, which could represent the mechanism behind the alleviation of depressive symptoms including psychomotor retardation.

Serotonin receptor subtypes 5-HT1A, 5-HT2A and 5-HT2C are expressed in motoneurons and modulate motoneuron excitability. Serotonergic neurons, which increase their discharge with motor activity, make numerous contacts with motoneurons; however, little is known about the adaptability of motoneuron serotonin receptor expression in response to exercise. The purpose of this study was to determine the effect of a 7-day treadmill exercise protocol on 5-HT1A, 5-HT2A and 5-HT2C receptor mRNA levels in rat lumbar motoneurons. Lumbar motoneurons of exercised and sedentary animals were collected via laser capture microdissection. RNA was isolated from these samples and real-time reverse transcription polymerase chain reactions were performed to determine differences in receptor mRNA levels between exercised and sedentary animals. It appears that 5-HT1A, 5-HT2A and 5-HT2C receptor mRNA levels are unaltered following 7 days of treadmill exercise; however, future research must be done to determine if an exercise effect exists when motoneurons are differentiated by type.

The development of novel selective 5-HT6 and 5-HT7 receptor antagonists is an ever-growing area of interest among medicinal chemists. The potential of developing a therapeutic agent useful as an antipsychotic or antidepressant, as well as the possibility to develop a drug for Alzheimer’s disease and obesity has led to an increase in synthesis of possible lead compounds. The synthesis of unfused biheteroaryl derivatives is described within. The derivatives have been evaluated for binding affinity at 5-HT2A, 5-HT6 and 5-HT7 receptors. The most potent 5-HT6 receptor antagonists include a benzene ring, a hydrophobic group and a protonated nitrogen atom. The most potent and selective compound synthesized is 1-[3-butyl-5-(thienyl)phenyl]-4-methylpiperazine. The binding site of the 5-HT7 receptor is similar to that of the 5-HT6 receptor and the most selective and potent 5-HT7 receptor antagonist also contains a potonated nitrogen atom and a hydrophobic group. The difference in selectivity between the 5-HT6 and 5-HT7 receptor antagonists is the aromatic ring. The most potent 5-HT7 receptor antagonist synthesized contains a pyridine ring instead of benzene, as in the 5-HT6 receptor antagonist. The most potent and selective 5-HT7 receptor antagonist is 1-[4-(3-furyl)-6-methylpyridin-2-yl]-4-methylpiperazine. The need to increase selectivity for both 5-HT6 and 5-HT7 receptors has led to the synthesis of flexible-chain linked derivatives and the results are described within.

In zebrafish, the ventilatory response to hypoxia first develops at 3 days post-fertilization (d.p.f.) before O2-chemoreceptive neuroepithelial cells (NECs) of the gill appear at 7 d.p.f. This indicates the presence of extrabranchial chemoreceptors in embryos and a developmental transition to primarily gill O2 sensing. This thesis examined the skin NECs, which reach peak density in embryos but decline as gill NECs appear. Exposure of embryos and larvae to chronic hypoxia prevented the loss of skin NECs, shifted peak basal ventilation to a later developmental stage, and induced a hypoventilatory response to acute hypoxia. Chronic exposure to hyperoxia rapidly diminished skin NECs, shifted peak ventilation to earlier stages and eliminated the response to acute hypoxia. Administration of the neurotoxin 6-hydroxydopamine degraded nerve terminals that contact skin NECs and reduced both basal ventilation frequency and the hypoxic ventilatory response. Thus, skin NECs are candidates for extrabranchial O2 chemoreceptors in developing zebrafish.

Fluoxetine (FLX), the active ingredient of Prozac™, is a member of the selective serotonin reuptake inhibitor (SSRI) class of anti-depressant drugs and is present in aquatic environments worldwide. Previous studies reported that FLX is an endocrine disruptor in fish, bioconcentrating in tissues including the brain. Evidence implicates that serotonin influences the activity of the hypothalamo-pituitary-interrenal (HPI) stress axis, thus exposure to FLX may disrupt the teleost stress response. This study examined in vitro cortisol production in rainbow trout (Oncorhynchus mykiss) head kidney/interrenal cells exposed to FLX and 14C-pregnenolone metabolism in head kidney microsome preparations of FLX-exposed trout. Results indicated that cells exposed in vitro to increasing concentrations of FLX had lower cortisol production and cell viability (versus control) and microsomes isolated from trout exposed to 54 μg/L FLX had higher pregnenolone metabolism versus those of control and low FLX-exposed (0.54 μg/L) trout.

Depression is a major psychological disorder that affects a person's mental and physical abilities. The National Institute of Mental Health (NIMH) classified it as a serious medical illness. It causes huge economic, as well as financial impact on the people, and it is also becoming a major public health issue. Antidepressant drugs are prescribed to mitigate the suffering caused by this disorder. Different generations of antidepressants have been developed with dissimilar mechanisms of action. According to the Center for Disease Control, the usage of antidepressants has skyrocketed by 400 percent increase over 2005- 2008 survey period. This dramatic rise in usage indicates that these are the most prescribed drugs in the US. Even with the FDA mandated "black box" warning of increased suicidal thoughts upon use of selected antidepressants, these drugs are still being used at a higher rate. <br>All classes of antidepressants are plagued by side effects with mainly sexual dysfunction common among them. To avoid the adverse effects, an emphasis is to discover novel structural drug scaffolds that can be further developed as a new generation of antidepressants. The importance of this research is to discover structurally novel antidepressants by performing in silico virtual screening (VS) of chemical databases using the serotonin transporter (SERT). In the absence of a SERT crystal structure, a homology model was developed. The homology model was utilized to develop the first structure-based pharmacophore for the extracellular facing secondary ligand binding pocket. The pharmacophore captured the necessary drug-SERT interaction pattern for SERT inhibitory action. This pharmacophore was employed as one of the filters for VS of candidate ligands. The ten compounds identified were purchased and tested pharmacologically. Out of the ten hits, three structurally novel ligands were identified as lead compounds. Two of these compounds exhibited selectivity towards SERT; the remaining lead compound was selective towards the dopamine transporter and displayed cocaine inhibition. The two SERT selective compounds will provide new opportunities in the development of novel therapeutics to treat depression. <br>For dopamine transporter (DAT), the study was based on recently developed structurally diverse photo probes. In an effort to better understand the binding profile similarities among these different scaffolds, the photo probes were docked into DAT. The finger print analysis of the interaction pattern of docked poses was performed to identify the inhibitor-binding sites. <br>For mitogen activated protein kinase 5 (MEK5), given the lack of structural information, a homology model of MEK5 was developed to guide the rational design of inhibitors. Docking of known MEK5 inhibitors into the homology model was performed to understand the inhibitory interaction profile. Several series of analogues were designed utilizing the generated interaction profile. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD / Dissertation

Little is known about the adaptation of livestock to repeated transport. This study determined how repeated transport affected calf feed intake, plasma cortisol (CORT), post-transport behavior, and the expression of immune-related genes. Thirty-six 4-month-old Holstein steer calves were housed in groups of six with each group randomly assigned to either transport (T) or control (C) treatments. The T calves were hauled for 6 h in a 7.3 m x 2.4 m goose-neck trailer, at an average density of 0.87 m2/calf, every 7 d for five consecutive weeks. Individual daily intake was determined using Calan gate feeders. Blood samples were obtained in the trailer or home pen via jugular venipuncture before loading, and after 2, 4, and 6 h of transport. Samples were analyzed for CORT, serotonin, tryptophan, and the gene expression of interleukin-4 (IL-4), interleukin-6 (IL-6), chemokine (C-X-C motif) receptor 2, interleukin-12, toll-like receptor-4, toll-like receptor-2, and 5-hydroxytryptamine receptor 2A in leukocytes. Behavior was recorded for transported calves at 5-min intervals for 1 h after return to their home pens. The C calves had a higher feed intake than T calves overall (P = 0.01), on the day of transport (P = 0.007), and the day after transport (P = 0.02). Pre-transport CORT concentrations did not differ by treatment (P = 0.77) or trial (P = 0.32). However, the T calves had higher response CORT concentrations than C calves during Transport 3 (P = 0.006), Transport 4 (P = 0.001) and Transport 5 (P = 0.02). The T calves had the highest response CORT concentrations after 2 h of transport and the lowest response CORT concentrations after 6 h of transport (P < 0.0001). Treatment did not affect gene expression in leukocytes, however, the expression of IL-4 (P = 0.01) and IL-6 (P = 0.05) was significantly lower after 2 h of transport than any other sampling times. These results suggest conflicting conclusions on whether the calves started to acclimate after being transported five times. However, CORT and gene expression differences occurred in response to the blood sampling regimen, which may provide insight to how calves acclimate during prolonged stress.

Fear memories, here defined as learned associations between a stimulus and a physiological fear reaction, are formed through fear conditioning. In animals, fear memories, present in the lateral amygdala, undergo reconsolidation after recall. Moreover, this reconsolidation process can be disrupted both pharmacologically and behaviourally, resulting in a reduced fear response to the stimulus. This thesis examines the attenuation of fear memories by disrupting reconsolidation in humans, using measures of both the central and peripheral nervous system activity. Serotonergic and dopaminergic genes have previously been tied to both fear conditioning and anxiety disorders, where fear conditioning mechanisms are important. In order to evaluate the possible role of fear memory reconsolidation mechanims in the effect on fear and anxiety by these genes, this thesis also compare the reconsolidation disruption effect between different serotonergic and dopaminergic genotypes. Study I examined the attentuation of fear memories by disrupting reconsolidation in humans using reacquisition as a measure of the return of fear. Moreover, study I investigated the impact of differences in serotonergic and dopaminergic alleles on this process. Study II examined the attentuation of fear memories by disrupting reconsolidation in humans using reinstatement as a measure of the return of fear. Study II also investigated the impact of differences in serotonergic and dopaminergic alleles on the process of fear memory reconsolidation. Study III used psychophysiology and fMRI to localize the functional neural activity mediating the fear memory reconsolidation disruption effect. In summary, this thesis provides evidence that fear memories are attenuated by reconsolidation disruption in humans and that serotonergic and dopaminergic alleles influence this process. Moreover, this thesis support that human fear memory reconsolidation is amygdala-dependent, suggesting an evolutionary shared memory mechanism.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill5 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.