Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 231 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

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.

Introduction. Allopregnanolone and pregnanolone (neuroactive metabolites of progesterone) act as positive modulators of the GABAA receptor system which is the major inhibitory system in CNS. Contradictory results on the effect of GABAA receptor modulators are reported. Beneficial properties such as anaesthesia, sedation, and anxiolysis are reported as well as adverse, anxiogenic and aggressive effects. It has been suggested that GABAA receptor agonists have bimodal effects. Low concentrations increase an adverse, anxiogenic effect, whereas higher concentrations show beneficial, calming properties. Aims. To investigate if progesterone treatment induces adverse mood in postmenopausal women and if the severity in mood symptoms is related to progesterone, allopregnanolone or pregnanolone serum concentrations. To evaluate differences in steroid concentrations induced by different doses and routes of administration of progesterone. Methods. Two randomised, placebo-controlled, double-blind crossover studies of postmenopausal women were performed. Subjects were treated with estradiol continuously. Different doses of progesterone, given vaginally or orally, were added sequentially during the last 14 days of each treatment cycle. Daily symptom ratings were kept using a validated rating scale. Blood samples for progesterone, allopregnanolone and pregnanolone analyses were collected during each treatment cycle. A study regarding the pharmacokinetics after ingestion of low-dose oral progesterone was conducted with postmenopausal women. Blood samples for the analyses of progesterone, allopregnanolone and pregnanolone were collected and pharmacokinetic parameters were calculated. Results. Certain postmenopausal women on sequential HT with vaginal and oral progesterone experience mood deterioration during the progesterone phase while on a low dose of progesterone but not on higher doses or the placebo. Negative mood symptoms occurred when the serum concentration of allopregnanolone was similar to endogenous luteal phase levels, whereas lower and higher concentrations had no effect on mood. Pharmacokinetic analyses show that low-dose oral progesterone can be used as a prodrug to allopregnanolone when the aim is to achieve physiological concentrations of allopregnanolone. Conclusions. A bimodal association between allopregnanolone concentration and adverse mood is observed in postmenopausal women treated with progesterone. The addition of low-dose progesterone to estradiol induces adverse mood in postmenopausal women, whereas higher doses and placebo have no mood-deteriorating effect.

No description available.

Succinic semialdehyde dehydrogenase (ALDH5A1) deficiency (SSADH-d) is an autosomal recessive, inborn error of gamma-aminobutyric acid (GABA) metabolism that results in psychomotor retardation, ataxia and seizures. A mouse model of SSADH-d (the Aldh5a1-/- mouse) was created to study the pathophysiology and treatment of SSADH-d. Aldh5a1-/- mice have psychomotor retardation and a progressive seizure phenotype results in death around P25. The present experiments tested the effects of a ketogenic diet in the treatment of Aldh5a1-/- mice. The KD was found to prolong the lives of Aldh5a1-/- mice by >300% while significantly delaying the onset the ataxia and preventing weight loss that is seen in untreated Aldh5a1-/- mice. Electrophysiological recordings revealed a corresponding decrease in seizures in KD fed mutants, as compared to control diet (CD) fed mutants. We assessed spontaneous miniature postsynaptic currents (mPSC) in CD and KD fed mutants. We found that CD fed mutants had significantly decreased inhibitory mPSC (mIPSC) activity compared to CD fed wildtype controls. mIPSC activity was restored in KD fed Aldh5a1-/- mice. A similar effect was found in [35S]TBPS binding experiments. TBPS binding was significantly reduced in CD fed Aldh5a1-/- mice, but restored in KD fed mutants. Plasma analysis revealed that an elevation of serum beta-hydroxybutyrate may play a role in the KD’s effects. The KD led to a significant elevation in the number of hippocampal mitochondria in mutant mice. Further, the KD was able to normalize the deficiencies in the hippocampal ATP levels seen in the Aldh5a1-/- mice. The present data suggest that the KD is able to significantly improve the Aldh5a1-/- phenotype. The effect of the KD on mIPSC activity is novel and furthers our understanding of how the KD may exert its effects. The mitochondrial studies confirm the findings of others, that the KD elevates the number of mitochondria. The KD also restores ATP deficiencies in Aldh5a1-/- mice, which is a novel finding. Together, these show that the KD may be an effective treatment for SSADH-d in humans. These data also further our understanding of the KD’s mechanisms of action.

Succinic semialdehyde dehydrogenase (ALDH5A1) deficiency (SSADH-d) is an autosomal recessive, inborn error of gamma-aminobutyric acid (GABA) metabolism that results in psychomotor retardation, ataxia and seizures. A mouse model of SSADH-d (the Aldh5a1-/- mouse) was created to study the pathophysiology and treatment of SSADH-d. Aldh5a1-/- mice have psychomotor retardation and a progressive seizure phenotype results in death around P25. The present experiments tested the effects of a ketogenic diet in the treatment of Aldh5a1-/- mice. The KD was found to prolong the lives of Aldh5a1-/- mice by >300% while significantly delaying the onset the ataxia and preventing weight loss that is seen in untreated Aldh5a1-/- mice. Electrophysiological recordings revealed a corresponding decrease in seizures in KD fed mutants, as compared to control diet (CD) fed mutants. We assessed spontaneous miniature postsynaptic currents (mPSC) in CD and KD fed mutants. We found that CD fed mutants had significantly decreased inhibitory mPSC (mIPSC) activity compared to CD fed wildtype controls. mIPSC activity was restored in KD fed Aldh5a1-/- mice. A similar effect was found in [35S]TBPS binding experiments. TBPS binding was significantly reduced in CD fed Aldh5a1-/- mice, but restored in KD fed mutants. Plasma analysis revealed that an elevation of serum beta-hydroxybutyrate may play a role in the KD’s effects. The KD led to a significant elevation in the number of hippocampal mitochondria in mutant mice. Further, the KD was able to normalize the deficiencies in the hippocampal ATP levels seen in the Aldh5a1-/- mice. The present data suggest that the KD is able to significantly improve the Aldh5a1-/- phenotype. The effect of the KD on mIPSC activity is novel and furthers our understanding of how the KD may exert its effects. The mitochondrial studies confirm the findings of others, that the KD elevates the number of mitochondria. The KD also restores ATP deficiencies in Aldh5a1-/- mice, which is a novel finding. Together, these show that the KD may be an effective treatment for SSADH-d in humans. These data also further our understanding of the KD’s mechanisms of action.

No description available.

Activation of muscarinic acetylcholine receptors (mAChRs) has pronounced effects on GABAergic interneurons, including depolarization of their resting membrane potential, and increasing their action potential and vesicular release frequency. Moreover, postsynaptic mAChR activation in hippocampal pyramidal neurons reduces the expression of the K+-Cl- cotransporter (KCC2). However, whether mAChR activation modulates the expression of disinhibition-mediated synaptic plasticity has not been examined. I induced inhibitory long-term potentiation (LTP) by applying coincident pre/postsynaptic stimulation in the hippocampus. This plasticity was characterized by an increase in the postsynaptic potential (PSP) amplitude and a depolarization in the inhibitory postsynaptic potential (IPSP) reversal potential; characteristics of disinhibition-mediated LTP (dmLTP). Activation of mAChRs during this plasticity induction protocol prevented the expression of dmLTP via a presynaptic downregulation of transmitter release. This was concluded from evidence that the PSP amplitude and IPSP reversal potential were unaltered, and paired-pulse depression occurred following plasticity induction in the presence of mAChR activation.

Plusieurs variables biologiques, psychologiques, ainsi que des différences culturelles, ont été mises en cause afin d'expliquer la différence de perception de la douleur existante entre les hommes et les femmes. Il est connu que les hormones sexuelles gonadiques influencent la réponse nociceptive chez l’animal et chez l’humain. Le cerveau a aussi la capacité de synthétiser ses propres "hormones sexuelles", les neurostéroïdes. Les objectifs étaient: 1) évaluer les facteurs influençant de perception de la douleur chez les hommes et les femmes, 2) mettre en relation les niveaux d’hormones gonadiques et adrénergiques avec les symptômes cliniques et la perception de la douleur chez des sujets fibromyalgiques et sains, et 3) évaluer l'implication des hormones gonadiques et de leurs métabolites 3?5?-réduits dans la transmission de la douleur et l'efficacité des mécanismes de contrôle descendants de la douleur (MCDD) chez les mâles et les femelles. Résultats: 1) Des analyses statistiques ont permis de conclure que bien que plusieurs facteurs psychologiques soient différents entre les hommes et les femmes, et qu'ils influencent aussi la douleur, il semble y avoir des différences physiologiques intrinsèques qui font que les hommes sont moins sensibles et plus tolérants à la douleur que les femmes. 2) Nous avons évalué l'implication des hormones gonadiques et adrénergiques chez des sujets sains et des sujets fibromyalgiques. Un déséquilibre des androgènes corrèle avec l'importance des symptômes cliniques et de la sensibilité/tolérance à la douleur expérimentale dans cette pathologie. 3) Les hormones gonadiques ont une implication à la fois sur les mécanismes de transmission et de modulation de la douleur. Leurs métabolites 3?5?-réduits, quant à eux, affectent uniquement la transmission nociceptive, mais de façon sexe-dépendante. Lors d'un paradigme de retrait de progestérone mimant la phase lutéale du cycle menstruel, la capacité d'activation des MCDD est particulièrement diminuée et cet effet semble être dû à la présence de métabolites 3?5?-réduits. Ce projet a mis en évidence la complexité de la modulation de la douleur chez les hommes et les femmes. En effet, plusieurs facteurs physiologiques et psychologiques ont été identifiés et sont impliqués dans un réseau d'interactions complexes qui déterminent la réponse douloureuse physiologique et pathologique sexe-spécifique. [symboles non conformes]