Browsing by Author "Rauvala, Oskari"

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.