Toll like receptors (TLRs) belong to a family of pattern recognition receptors that recognise broadly shared molecules found on pathogens referred to as pathogen associated molecular patterns (PAMPs). TLRs are well known for their involvement in innate immunity however despite their presence in the CNS, our knowledge of their function in the CNS is limited. Therefore in the present study, we investigated the cellular localisation of TLR3 and the consequence of its activation on synaptic activity. Primary hippocampal cultures using P1-2 rats were prepared and used experimentally between 10-14DIV. Standard whole cell patch clamp electrophysiology recordings in voltage and current clamp were used to monitor ion channel function and synaptic activity respectively. Experiments revealed TLR3 expression in neurons, astrocytes and oligodendrocytes within the cultures. Synaptically driven spontaneous action potential (AP) firing was significantly reduced by short-term application (5min) of the TLR3 specific activator, poly I:C (25μg/ml and 200μg/ml). Furthermore long-term poly I:C application (1hr) showed a dramatic reduction in AP firing (1μg/ml and 25μg/ml). Investigations were carried out to determine the mechanisms underlying these effects. Short-term application of poly I:C (200μg/ml) had no effect on the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs). However, a significant reduction on sodium current was observed. In contrast, long-term application of poly I:C (25μg/ml) resulted in a significant reduction in mEPSC amplitude, frequency and peak sodium and potassium current. Furthermore long-term application of poly I:C (25μg/ml) resulted in a significant reduction of surface AMPAR expression. These underlying effects of TLR3 activation require the activation of the TRIF pathway as shown by the mutant version of TLR3 blocking the effect on sodium current. In summary, these data imply that TLR3 activation modulates hippocampal synaptic activity through multiple mechanisms. This data might provide further insight into how this contributes to virally-mediated behavioural changes.
|Date of Award||23 Feb 2016|
- University Of Strathclyde
|Sponsors||University of Strathclyde & BBSRC (Biotech & Biological Sciences Research Council)|
|Supervisor||Trevor Bushell (Supervisor) & Andrew Paul (Supervisor)|