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Browsing by Subject "Plasticity"

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  • Haikonen, Joni (2019)
    Kainate receptors are known to regulate neuronal function in the brain (Li, H., & Rogawski, M. A. (1998), Braga, M. F. et al. (2004), Lerma & Marques (2013), Carta, M (2014)). In the amygdala, they have been shown to affect synaptic transmission and plasticity, as well as glutamate and γ-aminobutyric acid (GABA) release (Li, H. et al. (2001). Braga, M. F. et al. (2003), Braga, M. F. et al. (2009), Aroniadou-Anderjaska, V. et al. (2012), Negrete‐Díaz, J. V. et al. (2012)), however, their role during development of the amygdala circuitry is not known. In the present study, we wished to understand how GluK1 kainate receptors regulate synaptic population activity and plasticity in the developing amygdala by using extracellular field recordings in P15-18 Wistar Han rat pup brain slices. Since field excitatory postsynaptic potentials (fEPSPs) are not commonly measured from the amygdala, we first sought to pharmacologically characterize the basic properties of the extracellular signal, recorded from the basolateral amygdala in response to stimulation of the external capsulae (EC). Having confirmed the validity of the fEPSP as a measure of postsynaptic population response, we were able to show that blocking GluK1 with (S)-1-(2-Amino-2-carboxyethyl)-3-(2-carboxy-5-phenylthiophene-3-yl-methyl)-5-methylpyrimidine-2,4-dione (ACET), a selective GluK1 antagonist, had no effect on the fEPSP. Furthermore, activation of GluK1 with RS-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), a GluK1 agonist, reduced the amplitude of the fEPSP, without affecting its slope, suggesting an increase in inhibitory signaling within the network. Blocking GABAergic activity with GABAA- receptor antagonist picrotoxin significantly reduced the effects of ATPA. Additionally, the increase in inhibitory signaling due to the activation of GluK1 was confirmed with whole-cell voltage clamp, by measuring spontaneous inhibitory postsynaptic current (sIPSC) frequency. Activation of GluK1 heavily increased sIPSC frequency in the basolateral amygdala neurons. Finally, we were also able to show that activation of GluK1 with ATPA strongly attenuates LTP induction. These results show that GluK1 kainate receptors play a vital role in the modulation of synaptic transmission and plasticity in the developing amygdala.
  • Levo, Martti (2023)
    Climate change is applying pressures to plant populations, which must adapt or move to retain fitness. A changing climate highlights the need for us to understand the potential that species possess to evolve in addition to any plastic responses. Approaches that allow the study of contemporary evolution, such as resurrection studies, have the capacity to provide insights into the responses of populations to these changes. In this resurrection experiment, seeds from seven populations of Hypericum perforatum collected from the UK and France, and their historic counterparts, were grown and subjected to four temperature treatments. Three traits were measured and compared between historic and contemporary populations: date of flowering, average seed weight and flower abundance. I found that temperature influenced date of flowering and flower abundance, leading to an overall earlier flowering time and an overall decrease in flower abundance with increase in temperature. The only significant difference between historic and contemporary populations was found in flower abundance - where, whilst flower abundance declined with increasing temperature, contemporary populations produced proportionally more flowers than historic populations per degree of temperature increase. These results suggest that plasticity allows this species to adjust its flowering phenology to retain fitness in warmer conditions but that evolution during the past decades may have selected for a decreased flower abundance at higher temperatures. These findings contribute to our overall understanding of how species have and will react under climate change, as we try to disentangle the roles that plasticity and evolution play in enabling populations to retain fitness under changing conditions.