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See detailDeletion of Melanin-Concentrating Hormone Receptor-1 gene accentuates D-amphetamine-induced psychomotor activation but neither the subsequent development of sensitization nor the expression of conditioned activity in mice
Tyhon, Amélie ULg; Lakaye, Bernard ULg; Grisar, Thierry ULg et al

in Pharmacology, Biochemistry & Behavior (2008), 88

The present study aimed to test the hypothesis that mice lacking the MCHR1 receptor (Melanin-Concentrating Hormone Receptor-1) present an elevated vulnerability towards the neurobehavioural effects of D ... [more ▼]

The present study aimed to test the hypothesis that mice lacking the MCHR1 receptor (Melanin-Concentrating Hormone Receptor-1) present an elevated vulnerability towards the neurobehavioural effects of D-amphetamine, presumably due to previously established up-regulations of dopamine D1 receptors in these mice. We examined the psychomotor effects of five once-daily injections of 1.5 and 3 mg/kg D-amphetamine (i.p.) or ten once-daily injections of 2.25 mg/kg D-amphetamine in knockout (KO) mice lacking the MCHR1 receptor. The first injection of Damphetamine induced a greater psychomotor response amongst the KO mice at 2.25 and 3.0 mg/kg. On all subsequent D-amphetamine injections, KO mice still showed greater levels of psychomotor activity than the WT mice, but with no between-genotype difference in the rate of development of sensitization (similar slopes of the curves). Furthermore, 24 h after the last injection of 2.25 mg/kg D-amphetamine both genotypes exhibited a significant post-sensitization conditioned activity. Thus, MCHR1 receptors are likely not deeply involved in the mechanisms of induction of sensitization and related conditioned activity induced by D-amphetamine, albeit our results confirm a contribution of these receptors to the mechanisms of the acute effects of that drug, possibly via an inhibitory action on the dopaminergic mesolimbic system. Our results do not support the hypothesis of a functional contribution of MCHR1 receptors to the addictive effects of D-amphetamine [less ▲]

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See detailAmphetamine- and cocaine-induced conditioned place preference and concomitant psychomotor sensitization in mice with genetically inactivated melanin-concentrating hormone MCH(1) receptor.
Tyhon, Amélie ULg; Lakaye, Bernard ULg; Adamantidis, Antoine ULg et al

in European Journal of Pharmacology (2008), 599(1-3), 72-80

The melanin-concentrating hormone MCH(1) receptor has been proposed to exert an inhibitory control on monoaminergic (especially dopaminergic) activity within the mesolimbic system, which underpins drug ... [more ▼]

The melanin-concentrating hormone MCH(1) receptor has been proposed to exert an inhibitory control on monoaminergic (especially dopaminergic) activity within the mesolimbic system, which underpins drug seeking and reward. That hypothesis predicts that an inactivation of these receptors should enhance the sensitivity to drug rewarding effects. To test that prediction, we examined the propensity of mice lacking the melanin-concentrating receptor (MCH(1) KO) and their intact counterparts (WT) to form cocaine- and amphetamine-induced conditioned place preference. The conditioned rewarding effects induced by 0.375, 0.75, 1.5 and 3 mg/kg amphetamine were assessed in two sub-experiments and those induced by 1, 2, 4 and 8 mg/kg cocaine in two other sub-experiments. All mice were tested under saline for place preference 24 h following four every-other-day conditioning trials and an initial pre-conditioning session under saline. Most of the cocaine and amphetamine doses induced place preference, but without any genotype difference being revealed. Also, none of the cocaine doses induced psychomotor sensitization during conditioning, whereas amphetamine generated clear-cut dose-dependent sensitization in both genotypes. Albeit MCH(1) KO mice exhibited higher levels of psychomotor activation, the rates of sensitization were comparable across genotypes at 1.5 and 3 mg/kg amphetamine. Moreover, 0.375 and especially 0.75 mg/kg amphetamine produced a slight but yet significant sensitization in MCH(1) KO but not in their WT counterparts. Despite such an effect, the results cannot be considered as unambiguously supportive of the tested prediction. [less ▲]

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See detailDisrupting the melanin-concentrating hormone receptor 1 in mice leads to cognitive deficits and alterations of NMDA receptor function.
Adamantidis, Antoine ULg; Thomas, Elizabeth; Foidart, Agnès ULg et al

in European Journal of Neuroscience (2005), 21(10), 2837-44

In order to investigate the physiological properties of the melanin-concentrating hormone (MCH) we have generated and used mice from which the MCH receptor 1 gene was deleted (MCHR1(Neo/Neo) mice ... [more ▼]

In order to investigate the physiological properties of the melanin-concentrating hormone (MCH) we have generated and used mice from which the MCH receptor 1 gene was deleted (MCHR1(Neo/Neo) mice). Complementary experimental approaches were used to investigate alterations in the learning and memory processes of our transgenic model. The ability of the knockout strain to carry out the inhibitory passive avoidance test was found to be considerably impaired although no significant differences were observed in anxiety levels. This impaired cognitive property prompted us to explore modifications in N-methyl D-aspartate (NMDA) responses in the hippocampus. Intracellular recordings of CA1 pyramidal neurons in hippocampal slices from the MCHR1(Neo/Neo) mice revealed significantly decreased NMDA responses. Finally, using in situ hybridization we found a 15% reduction in NMDAR1 subunit in the CA1 region. These results show for the first time a possible role for MCH in the control of the function of the NMDA receptor. [less ▲]

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