Dopaminergic control of astrocytic calcium dynamics in situ and its potential effect on local synaptic activity

Astrocytes in culture display large cytosolic calcium increases upon stimulation with dopamine, however the mechanism and physiological significance of this calcium response is still unknown. In this thesis, I demonstrate that hippocampal astrocytes in situ respond to dopamine with similar large calcium transients. I also describe a novel astrocyte calcium decrease, which appears specific to dopaminergic stimulation. Dopamine is a potent neuromodulator of hippocampal synaptic activity, as are astrocytes. However, I found no evidence to suggest that dopamine-induced calcium transients in astrocytes affect excitatory synaptic transmission and its short-term plasticity in the hippocampal stratum radiatum. In perforant path - CA1 pyramidal synapses of stratum lacunosum-moleculare, astrocytes were found to lessen the inhibitory effect of dopamine on evoked PTP. This work shows for the first time that astrocytes in situ can robustly respond to dopamine with a complex Ca2+ signal thus may participate in dopaminergic signalling in the brain