ABSTRACT
Astrocytes are a key element of brain connectivity because they regulate neuronal communication at
synapses. Bergmann glial cells (BGCs), a major type of astrocytes in the cerebellum, are intimately associated
with excitatory glutamatergic synapses between Purkinje cell (PC) spines and parallel fibers or climbing fibers,
playing a significant role in synaptic stability and long-term plasticity. BGCs express a high density of Ca2+-
permeable GluA2-lacking AMPA receptors (CP-AMPARs), which are required for the maintenance of the BGC
processes that ensheath PC spine synapses. Genetic deletion of CP-AMPARs results in impaired associative
motor learning. Our preliminary data indicate that CP-AMPARs in BGCs are subject to dopaminergic (DAergic)
modulation. Pharmacological stimulation of D1 receptors enhances CP-AMPARs-mediated currents in BGCs,
and phosphorylates the GluA1 subunit at Ser845. Using transgenic mice with fluorescently-tagged D1
receptors and anterograde axonal tracing, we determined that D1 receptors are exclusively expressed in
BGCs, which receive DAergic afferents from the ventral tegmental area and substantia nigra pars compacta in
the midbrain. Intriguingly, D1 receptor activation also increases PC firing and locomotor activity. Based on
these preliminary findings, we hypothesize that activation of D1 receptors induces insertion of CP-
AMPARs in BGCs, which in turn modulates PC synaptic function. To test this hypothesis, we will use a
combination of experimental approaches, including whole-cell recordings with optogenetic stimulation,
immunocytochemistry, molecular biology, and pharmacology. We propose two Specific Aims: (1) characterize
membrane insertion of GluA1 in Bergmann glial cells induced by DA; and (2) define the role of DAergic
modulation of Bergmann glial cells in PC activity. We expect to generate conceptually novel knowledge
regarding DA modulation of cerebellar circuitry function by defining the contribution of CP-AMPARs in BGCs to
synaptic function in PCs. These new findings will not only deepen our understanding of DAergic function in the
healthy brain, but also provide additional avenues for the development of disease-modifying therapies for
motor-related neurological disorders.