[Abstract Title]. - Society for Neuroscience

242. Glial Neuronal Interactions: Glutamate and Calcium
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 242.7/I2
Topic: B.11.a. Synapses
Support: Wellcome Trust
Human Frontier Science Program
Medical Research Council
Title: LTP induction changes the morphology of astrocytes in the CA1 region of the
hippocampus in vitro
Authors: *C. HENNEBERGER 1 , N. MEDVEDEV 2 , M. G. STUART 2 , D. A. RUSAKOV 1 ;
1 Inst. of Neurol., Univ. Col. London, London, United Kingdom; 2 Dept. of Biol. Sci., The Open
Univ., Milton Keynes, United Kingdom
Abstract: Astrocytes are reported to sense and modulate neuronal activity. One important aspect
of astrocyte function is the fast clearance of neurotransmitter in the vicinity of synapses. This
relies on a high density of neurotransmitter transporters expressed on the membranes of fine
astrocytic processes that surround synaptic structures. Whether the spatial relationship between
astrocytes and synapses is static or whether it responds to neuronal plasticity remains poorly
understood.
We combined recordings of field potentials, whole-cell currents and two-photon excitation
fluorescence imaging of astrocytes in the CA1 stratum radiatum in hippocampal slices obtained
from 3-4 week old Sprague Dawley rats. Alexa 594 and Oregon Green BAPA-1 were included in
the intracellular solution to monitor fine astrocyte morphology and Ca 2+ dynamics.
Morphological changes were quantified in real time as changes in the tissue volume fraction
occupied by the astrocyte, dendritic image entropy, fluorescence recovery after photobleaching
and also using an image segmentation algorithm.
We found that astrocyte morphology was modified by electrical stimulation protocols that
induced long-term potentiation (LTP) of transmission at Schaffer collateral synapses. The
observed changes, which were sensitive to NMDA receptor blockade, can be best explained as
partial retraction of fine astrocyte processes. Electron microscopy investigation of biocytin-filled
and reconstructed astrocytes that underwent potentiation protocols is currently under way.
Disclosures: C. Henneberger , None; D.A. Rusakov, None; N. Medvedev, None; M.G.
Stuart, None.