Browsing by study line "Farmakologi"
Now showing items 41-42 of 42
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(2023)Current pharmacological treatments for major depressive disorder leave many patients unresponsive to treatment or treatment response is delayed by weeks. More effective treatments with quicker effect onset are therefore needed. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonists has demonstrated sustained rapid antidepressant activity after single dose. Precise mechanisms behind this effect are unknown, however some crucial contributors to ketamine-induced behavioural effects in rodents include phosphorylation of Tropomyosin receptor kinase B (TrkB), ribosomal protein s6 kinase (p70s6k), glycogen synthase kinase 3 (GSK3), mitogen activated protein kinases (MAPKs), and activation of α-amino-3-hydroxy-5- methyl-4- isoxazolepropionic acid receptors (AMPAR). Similar TrkB related signaling cascades are also activated with another NMDA receptor antagonist and a putative rapid-acting antidepressant, nitrous oxide (N2O). During acute effects of N2O, cortical excitation increases MAPK phosphorylation and upregulates expression of activity dependent immediate early genes (IEG; c-Fos and Bdnf IV). Phosphorylation of TrkB, GSK3 and p70s6k appearing only after N2O has been eliminated suggest that TrkB signaling is induced as an adaptive response to treatment. The first objective of this study was to corroborate previous results from our group to validate our gas administration set up and protein analysis protocol. To analyze N2O-induced phosphorylation of proteins implicated in ketamine’s behavioral effects in mice, we treated C57BL/6J male mice with either room air (control) or 65% nitrous oxide for 20 minutes. After gas exposure and 15-minute washout period, medial prefrontal cortex samples were dissected to be analyzed with western blotting. In this study nitrous oxide exposure did not induce increased TrkB signaling in nitrous oxide withdrawal. Another aim of this study was to investigate the involvement of AMPARs in inducing cortical excitation with N2O. Pretreatment of AMPAR antagonist (10 mg/kg, NBQX) or saline was given to C57BL/6J male mice 10 minutes prior to 1 hour exposure to 50 % O2 or 50 % N2O, a N2O dose previously shown to induce IEG expression. One hour after gas exposure mice were euthanized and mPFCs were dissected and analyzed with reverse transcriptase quantitative PCR (RT-qPCR). No regulation in IEG expression was induced with nitrous oxide, NBQX pretreatment or combination compared to control. Additional studies factoring in limitations of this study are needed to uncover the involvement of AMPAR in inducing cortical excitation and antidepressant-like behavioral effects of N2O in preclinical models of depression.
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(2023)Rodent studies indicate that the effects of pharmacological antidepressant treatments depend on the TrkB (tropomyosin-related kinase B) receptor of the neurotrophic factor BDNF (brain-derived neurotrophic factor). However, the mechanism by which TrkB signaling becomes active remains disputed. Our group proposes that the activation of TrkB signaling is a result of an indirect physiological adaptation to the drug treatment, which is supported by observations made with rapid-acting antidepressants ketamine and nitrous oxide. Previous studies indicate that the immediate effects of the drugs are followed by a sedative state resembling deep sleep, during which TrkB signaling becomes active. The sedative state is accompanied with a drop in core body temperature, and preliminary findings indicate that preventing the drug-induced hypothermia blocks TrkB signaling in the cortex. The purpose of this study was to investigate the effect of ambient temperature on TrkB signaling in the hippocampus following nitrous oxide administration. Nitrous oxide (65 % ad 100 % O2) was administered to adult male mice for 20 minutes. After the drug treatment the animals were kept in different recovery conditions: room temperature or a heightened ambient temperature of approximately 36 °C for 15 minutes. Following the recovery, the animals were euthanised, and hippocampus samples were collected from the animals. Levels of BDNF and TrkB signaling were analysed with ELISA and western blot, respectively. Nitrous oxide caused a significant drop in core body temperature, but this was not accompanied with increased BDNF levels or TrkB signaling. Evidence suggests that hippocampal atrophy contributes to depression, but the acute effects of antidepressant treatments on TrkB signaling in this brain area appear to be less pronounced than those seen in the prefrontal cortex. The findings indicate that nitrous oxide has a replicable hypothermic effect, but this is not associated with increased TrkB signaling in the hippocampus.
Now showing items 41-42 of 42