Adenosinergic modulation of hippocampal gamma oscillations: from single cell to whole animal

Gamma oscillations, synchronous network activity between 30 and 100 Hz, have been linked to higher cognitive functions. Adenosine receptor modulation has been shown to alter cognitive function in animals and humans. In this thesis the effects of adenosine receptor modulation on in vitro and in vivo hippocampal gamma oscillations were investigated as well as the underlying mechanisms. A₁-receptor activation selectively decreased gamma oscillations while blocking A₁-receptors and activating A_2A-receptors increased gamma oscillations. Increasing endogenous adenosine levels suppressed gamma oscillations while decreasing endogenous adenosine levels facilitated gamma oscillations in vitro. Sharp electrode current clamp and whole-cell voltage clamp experiments showed that A₁-receptor activation hyperpolarised resting membrane potential, reduced firing rate and EPSP amplitude and shifted the IPSC reversal potential to more negative potentials. Blocking A₁-receptors increased pyramidal cell excitability and increased excitatory synaptic transmission. The results in vivo were more ambiguous but A₁-receptor activation decreased power in all frequency bands indicating that adenosine receptors can modulate hippocampal gamma oscillations in vivo. A₁-receptor blockage had no consistent effect on in vivo hippocampal gamma oscillations. Adenosine receptors modulate gamma oscillations in rodent hippocampal slices but are difficult targets for developing treatments that have cognitive benefits because of their ambiguous effects in vivo.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Pietersen, Alexander Nicolaas Johannes

• R Medicine (General)
• QP Physiology