Astrocytes are star-shaped glial cells that are closely associated with chemical synapses. They express a variety of receptors for neurotransmitters, allowing them to respond to activity at nearby synapses with increases in intracellular Ca2+ levels or G protein activation. That, in turn, can trigger the release of a ‘gliotransmitter’, which can modulate transmitter release at nearby synapses or activate postsynaptic receptors. We are investigating how astrocytes can modulate activity in local circuits of neocortex and thalamus, on rapid, behaviorally relevant time scales.
Endocannabinoids belong to a group of non-classical neurotransmitters not stored in synaptic vesicles and often associated with retrograde signaling. Following a rise of postsynaptic Ca2+ concentration, endocannabinoids are released from the postsynaptic neuron and activate presynaptic cannabinoid receptors, thereby modulating transmitter release over several seconds. Cannabinoid receptors are widely expressed in prefrontal cortex, an area important for attention and working memory formation. Our experiments aim to understand how endocannabinoids are released during ongoing neuronal activity and how they control information flow through neuronal circuits. We are also interested in how endocannabinoid release is modulated by other transmitter systems in the prefrontal cortex, such as dopamine and serotonin.