Rong Ma – Developmental aspects of labile glutamate transmission in the hippocampus

Hälsa & medicin

Avhandling för medicine doktorsexamen vid Sahlgrenska akademin, Institutionen för neurovetenskap och fysiologi, Sektionen för fysiologi

8 mar 2024
09:00 - 12:00
Hörsal Arvid Carlsson, Academicum, Medicinaregatan 3, Göteborg
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Opponent och betygsnämnd

Opponent: docent Björn Granseth, Institutionen för biomedicinska och kliniska vetenskaper, Linköpings universitet, Linköping

Betygsnämnd: docent Thomas Carlsson (ordf.), biträdande professor Ann-Sofie Cans (CTH) och docent Erik Smedler

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Disputationen hålls på engelska

Glutamate as a neurotransmitter

Brain activity is largely controlled by synapses between neurons that use glutamate as a neurotransmitter, and how these glutamate synapses function. This also applies to the hippocampus, a brain region strongly linked to the ability to create episodic memories, i.e., remembering where, what, and when something happened in the past. Through this ability, the hippocampus is also crucial for detecting what is new by comparing an ongoing event with a previously stored one and ensuring that information about this is conveyed to the cortical areas of the brain that conveyed this event to the hippocampus. Pyramidal cells in the CA1 region of the hippocampus, which receive both previously stored information from CA3 pyramidal cells and ongoing sensory information from other cortical areas, can play an important role here.

In this thesis work, conducted on in vitro slice preparations from rats, the glutamate synapses that signal ongoing information are compared with the previously well-studied CA3-CA1 synapses that convey previously stored information. These synapses have been studied in both a functionally immature (2nd postnatal week) and mature (~1 month) hippocampus. The question has been whether the glutamate synapses that are supposed to interact with the CA3-CA1 synapses to produce a functional output from the hippocampus have properties specifically designed for this function, such as activity-dependent plasticity, and if so, whether these properties are present from the beginning or develop during hippocampal functional maturation.

Previous studies have shown that CA3-CA1 synapses change their plasticity during hippocampal maturation, initially participating in organizing a network and then strengthening it.

The main finding is that these other synapses to CA1 cells in both immature and mature hippocampi differ from the CA3-CA1 synapses in their properties but change during development in such a way that they function like CA3-CA1 synapses in the immature hippocampus. This change in these synapses may contribute to facilitating a continuous update of ongoing sensory input for comparison with learned information, and to conveying learned information to the appropriate cortical areas.