Lactate removal by inactive skeletal muscle was investigated using an isolated rat hindlimb perfusion model under conditions simulating recovery from maximal exercise. The purpose of this investigation was threefold: 1) to quantify the contributions of the oxidative, glyconeogenic, and triacylgylcerol (TG) synthesis pathways to lactate (La) removal, 2) to examine differences in La removal patterns in inactive skeletal muscle of various fiber types, and 3) to investigate the possible mechanisms for La and H⁺ removal by inactive muscle. Male Sprague-Dawley rats were perfused for 60 min, at rest with either a normal perfusate (NP) (N = 8) or a lactacidotic perfusate (LP) (N = 8). The LP perfusate was characterized by elevated concentrations of La (11.0 mMol), K⁺ (7.88 mMol), and hemoglobin (16.7 g·dl⁻¹) and a decreased pH (7.15). Arterial and venous perfusate and soleus (SOL), plantaris (PLT), and white gastrocnemius (WG) muscles were analyzed for various metabolite and ion concentrations. Analysis revealed increased rates of La uptake, glycerol release and C0₂ output in the LP versus the NP group. No difference was observed for O₂ uptake or glucose uptake between the two groups. Tissue anajysis revealed no significant change in muscle ATP, CP, glycogen, pyruvate, F-6-P or TG concentration pre versus post perfusion in both LP and NP groups. Significant increases were found in muscle La concentration (pre vs post and LP vs NP), with SOL having the highest concentration followed by PLT and WG. Muscle [F-1 ,6-diP], F-1 ,6-diP /F-6-P and pyruvate/F-1 ,6-diP ratios were elevated following LP perfusion indicating glyconeogenic inhibition. Muscle glucose levels decreased in the NP but not LP group, indicating a possible shift in substrate utilization in the LP group. In the LP group, total calculated La uptake by the 3 muscles was 61.0 umole, with 14% accumulating as tissue La post perfusion. Of the remaining 86%, 12-33% could be accounted for by oxidative metabolism, and 5-7% may have been involved in glycerol release. The remaining 60-75% was unaccounted for, but was hypothesized to have been involved in carbon cycling along the glycolytic/glyconeogenic pathway and/or in TG/FFA substrate cycling. No evidence was found of net glycogen synthesis from La. Increased H⁺ and K⁺ influx and HCO₃⁻ efflux were observed in response to lactacidotic perfusion. Sodium and Cl⁻ exchange patterns showed a net influx over 60 min of LP perfusion. Data from the ionic flux of the various strong ions and non-volatile H⁺ suggested that La is transported into inactive skeletal muscle by various mechanisms, including HLa diffusion, La/H⁺ cotransport, and possibly La/Cl⁻ exchange. The data also suggested that a number of regulatory mechanisms are activated in rat skeletal muscle to maintain intracellular [H⁺] and membrane potential during lactacidotic perfusion. From this investigation it was concluded that, in inactive muscle of the isolated rat hindlimb perfused for 60 min with a lactacidotic perfusate, patterns of La uptake and metabolic elimination are different from those previously observed for active muscle. The metabolic fates of La appear to be related to the ionic disturbances associated with La and H⁺ influx into inactive muscle. The net ionic movements across the inactive hindlimb appear to be related to the preferred metabolic pathways of La elimination, but whether or not a direct cause and effect relationship exists cannot be stated conclusively. / Thesis / Master of Science (MSc)

Substantia nigra neurons produce dopamine in response to cholinergic stimuli that may involve receptor operated Ca²⁺ -entry that has been associated with the transient receptor potential (Trp) proteins. There were 6 Trp isoforms reported when I started this work. I set out to determine which isoforms of Trp mRNA were expressed in the substantia nigra using the whole brain for comparison. I initially used RT-PCR to determine the Trp mRNA expression. Subsequently, I used competitive RT-PCR for quantifying the major isoforms. Finally, I confirmed my results by Co-RT-PCR of the major isoforms. Trp3 and Trp6 were found to be the predominant forms expressed in the substantia nigra and whole brain, while the levels of Trps 1, 2, 4 and 5 were very low in both. Estimation of mRNA levels using competitive RT-PCR showed that the Trp6 mRNA levels in substantia nigra and the whole brain were similar while those for Trp3 were significantly lower in the substantia nigra than in the while brain. Thus substantia nigra differs from the whole brain in its Trp expression. Properties of Trps 3 and 6 are not fully known. Trp3 is regulated by IP₃-receptor activation but both Trp 3 and 6 can be activated by diacylglycerol. How this relates to the signal transduction events in substantia nigra remains to be determined. / Thesis / Master of Science (MS)

Yes / Female hooded-Lister rats received either sub-chronic phencyclidine (PCP) (2 mg/kg, n=20) or vehicle (1 ml/kg, n=20) i.p. twice daily for seven days, followed by a seven-day washout period. Rats were challenged with acute PCP or vehicle and tested for locomotor activity to ensure hyperactivity was observed in the sub-chronic PCP treated rats. Rats were then tested on the elevated plus maze and in an open field for 10 minutes. Sub-chronic PCP did not significantly affect behaviour on the elevated plus maze or in the open field. In conclusion, sub-chronic PCP does not induce anxiety-like behaviour.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La douleur est un enjeu majeur de santé publique. Les prescriptions, et par voie de conséquence les intoxications au tramadol ont explosé récemment. Cet opioïde atypique présente des effets adverses variés, incluant dépression respiratoire, convulsions et syndrome sérotoninergique. Nos travaux chez le rat nous ont permis de montrer que la toxicité respiratoire induite par le tramadol était modérée mais aggravée en cas de co-administration de diazépam. Concernant les convulsions, celles-ci apparaissaient rapidement, étaient généralisées et accompagnées d’un état de mal épileptique. Ces convulsions n’étaient pas liées au syndrome sérotoninergique puis qu’indépendantes de la sérotonine. Nous avons suggéré à l’origine des convulsions induites par le tramadol, une modulation allostérique par cet opioïde des récepteurs GABAA entraînant probablement leur inhibition. Enfin, le syndrome sérotoninergique induit par le tramadol était caractérisé par des manifestations cliniques typiques accompagnées d’une encéphalopathie modérée à l’EEG. Nos résultats suggéraient aussi la nécessité d’une approche EEG systématique en complément des observations cliniques pour un diagnostic plus juste du syndrome sérotoninergique d’origine toxique. Pour reverser la toxicité neuro-respiratoire du tramadol, l’association diazépam/naloxone semblait être le traitement le plus efficace à proposer, abolissant les convulsions électro-cliniques, réduisant significativement les effets respiratoires délétères et faisant disparaître les signes sérotoninergiques. KGNOP1, un hybride bifonctionnel opioïde/anti-nociceptine, proposé comme alternative au tramadol pour traiter les douleurs neuropathique et par excès de nociception, présentait une efficacité et une sécurité d’emploi meilleures que le tramadol et la morphine, malgré des effets respiratoires délétères importants. En revanche, une tolérance rapide à ses effets analgésiques pourrait questionner son utilisation chez l’homme / Pain is a major public health issue. Tramadol prescriptions and their consequent poisonings have increased recently. This atypical opioid has various adverse effects including respiratory depression, seizures and serotonin syndrome. In our rat study, we demonstrated that tramadol-induced respiratory toxicity was moderate and worsened by diazepam co-administration. Tramadol-induced seizures were of rapid onset, generalized and accompanied by status epilepticus. Seizures were not related to serotonin syndrome since not induced by serotonin. We suggested tramadol-induced allosteric modulation of GABAA receptors resulting in its inhibition to explain tramadol-attributed seizures. Finally, tramadol-induced serotonin syndrome was responsible for well-characterized clinical symptoms accompanied by mild encephalopathy on the EEG. Interestingly, our results suggested that EEG study was required for an accurate diagnosis of serotonin syndrome in addition to the clinical observations. In order to treat tramadol-induced toxicity, diazepam/naloxone combination appears to be the best treatment to abolish tramadol-induced electro-clinic seizures, to reduce its deleterious respiratory effects, and to reverse its serotonin toxicity. KGNOP1, a bi-functional opioid/anti-nociceptin hybrid suggested as alternative compound to tramadol in the treatment of neuropathic and nociceptive pains, showed advantages with improved efficacy and safety in comparison to tramadol and morphine, despite important deleterious respiratory effects. However, the onset of rapid tolerance to its analgesic effects questioned the possible administration of this hybrid to humans

Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (leaves 207-221).

Th. 3e cycle--Biol. humaine et exp.--Paris 5, 1981. N°: 24.

Th. 3e cycle--Pharm.--Paris 5, 1981. N°: 22.

No description available.

Receptor-mediated phosphoinositide hydrolysis was studied in 3H-myo-inositol labelled rat cerebral cortical slices. Several CNS neurotransmitter receptor agonists stimulated the hydrolysis of inositol phospholipid(s). Maximal responses to receptor stimulation showed the order, muscarinic cholinergic > adrenergic > serotonergic > histaminergic. Potassium ion depolarisation and a Ca2+ ionophore also stimulated the accumulation of 3H-inositol phosphate(s). The metabolic sequence of muscarinic receptor-mediated phosphoinositide breakdown was examined in detail. Carbachol stimulated the sustained accumulation (> 45 min.) of 3H-Ins P1, 3H-Ins P1, 3H-Ins P2, 3H-Ins P3 and of a novel 3H-inositol phosphate identified as Ins-1,3,4,5-P4. Kinetic studies showed that muscarinic receptor activation results in the rapid (< 5 sec.) increased accumulation of 3H-Ins P2, 3H-Ins P3 and 3H-Ins P4 while the onset of 3H-Ins P1 accumulation is delayed. Using hplc, the Ins P3 fraction was resolved into two components with the retention times of Ins-1,3,4-P3 and Ins-1,4,5-P3. Stimulated accumulation of Ins-1,3,4-P3 was preceded by that of the other polyphosphates. The probable formation of Ins-1,3,4-P3 via Ins-1,3,4,5-P4 dephosphorylation is discussed. A phospholipid precursor for Ins-1,3,4,5-P4 could not be identified but production of this molecule via an ATP-dependent, Ins-1,4,5-P3 3-kinase was confirmed. Studies of the rates at which the separate 3H-inositol phosphates are hydrolysed in stimulated tissue suggest considerable flux through this kinase reaction and indicate that the majority of the 3H-Ins P1, and 3H-Ins P2 accumulating in response to agonist result from 3H-tris- and 3H-tetrakisphosphate metabolism. Pharmacological data support these conclusions for conditions of both high and low receptor occupancy. Lithium ions markedly affected muscarinic receptor-mediated 3H-inositol phosphate metabolism, dose-dependently potentiating stimulated 3H-Ins P3, and 3H-Ins P2 accumulations while concomitantly attenuating those of 3H-Ins P3 and particularly 3H-Ins P4. The latter effects were half-maximal at 1 mM Li+, exhibited a delayed onset, were not related to receptor desensitization but may be indirect consequences of Ins P1 phosphomonoesterase inhibition. The significance of these actions is discussed in the context of the potential second messenger roles of Ins-1,4,5-P3 and Ins-1,3,4,5-P4.