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.

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.

Increasingly, individuals in New Zealand are taking "herbal highs" with little knowledge of their possible long-term effects. Benzylpiperazine (BZP) is the predominant base drug in most herbal highs. The limited research into BZP has suggested that it produces similar effects to amphetamine, but could be 10 times less potent. There are to date, however, no long-term behavioural studies of BZP exposure. This study therefore, investigated effects of BZP exposure in adolescent male and female rats on subsequent measures of anxiety-like behaviours in adulthood. One group of experimental animals was treated daily with BZP, whereas another group received the same total amount of drug via a four day "binge" regime. The results suggested that, when observed in a Y-maze, social interaction test and a light/dark emergence test, BZP-treated rats were more anxious than control animals. In the Y-maze, male controls were more active than female controls, but BZP-treated females were more active than treated males. Results of this interaction indicate that the male rats may have been more affected by the administration of BZP during adolescence than females. Additionally, rats given the binge dose regime showed significantly increased anxiety in the Y-maze relative to the daily-exposed or control rats'. This suggests that larger quantities of BZP over a shorter time frame produce more detrimental effects than smaller quantities of BZP over a longer time frame. Overall, it would appear that the administration of BZP to adolescent animals produces behavioural changes in emotionality that are detectable in adulthood.

Intracellular recordings were made from neurones of the rat locus coeruleus (lc) contained within a brain slice maintained <i>in vitro</i>. When applied to the slice in known concentrations, K opioid receptor agonists produced a concentration-dependent, naloxone-reversible depression of the electrically evoked excitatory post-synaptic potential (epsp). This effect of K agonists was observed in the absence of changes in the membrane potential or input resistance of the post-synaptic cell. Similarly, the K agonists had no effect on the tetrodotoxin-resistant action potential waveform. Naloxone antagonised the response to U50488 with an apparent dissociation equilibrium constant (K<SUB>d)</SUB> of 28 nM, consistent with the response being mediated via K opioid receptors. In contrast, u opioid receptor agonists caused a membrane hyperpolarisation concomitant with a fall in neuronal input resistance, and depressed the tetrodotoxin-resistant action potential. These effects were concentration-dependent and antagonised by naloxone; the hyperpolarising action of [D-Ala<SUP>2</SUP> , NMePhe<SUP>4</SUP> , Gly-ol<SUP>5</SUP> ] enkephalin (DAGO) was antagonised by naloxone with a K<SUB>d</SUB> of 1.5 nM. These findings are in agreement with previous reports that u receptor activation increases a potassium conductance in lc neurones. The epsp was depressed, but not abolished, by the excitatory amino acid antagonists, 2-amino-5-phosphonovaleric acid (2APV) and kynurenic acid, suggesting that the epsp was at least partly mediated by an excitatory amino acid. U50488 did not depress the depolarisation produced by local application of L-glutamic acid. In addition to the epsp, a noradrenergic inhibitory post-synaptic potential (ipsp) could be evoked in lc neurones. U50488 depressed the ipsp, but this effect was not reversed by naloxone and therefore not mediated via opioid receptors. U50488 had no effect on the all or nothing depolarising potential which could be evoked in a proportion of lc neurones. The effect of U50488 on the epsp was reduced when experiments were performed in the presence of agents - either barium, quinine or 4-aminopyridine - which block potassium conductances. An <i>in vitro</i> autoradiographic study of <SUP>3</SUP> H bremazocine binding within the lc revealed that the majority of binding was displaced by a combination of unlabelled DAGO and [D-Ser<SUP>2</SUP> ] Leu enkephalin Threonine (DLSET) and so represented u sites. A significant proportion however, was displaceable by unlabelled U50488 and thus represented K binding sites. It is concluded that K opioid receptors are situated pre-synaptically within the lc and when activated depress excitatory synaptic transmission.