[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#: 242.9/I4
Topic: B.11.b. Cell biology and signalling
Support: The Council of Scientific and Industrial Research (CSIR) Grant
Title: Acute effect of 17β-estradiol on signaling between astrocytes and neurons in mixed
hippocampal cultures
Authors: *S. P. RAO 1 , S. K. SIKDAR 2 ;
1 Psychiatry/MRRC, Semel Inst, UCLA, Los Angeles, CA; 2 Mol. biophysics unit, Indian Inst. of
Sci., Bangalore, India
Abstract: The ovarian steroid hormone 17β-estradiol, in addition to its classical genomic effects
in the brain through intracellular estrogen receptors, can bring about actions that are rapid in
onset via a plasma membrane-associated form of its receptor. In the hippocampus, estrogen
receptors have been observed at extranuclear sites on both neurons and astrocytes suggesting a
complex interplay between the two cell types in mediating the effects of the hormone. Neuronal
activity can trigger intracellular calcium elevations in astrocytes, in turn leading to release of
gliotransmitters that can modulate neuronal activity and synaptic transmission.
We investigated the functional consequences of acute (5 min) estradiol treatment on astrocyteastrocyte
and astrocyte-neuron signaling in rat hippocampal cultures using calcium imaging and
electrophysiological techniques. Mechanical stimulation of an astrocyte in fluo-3 AM loaded
cultures evoked a calcium rise in the stimulated astrocyte followed by calcium elevations in the
surrounding astrocytes and neurons. Following acute treatment with estradiol, the amplitude of
the calcium responses in the surrounding astrocytes and neurons was attenuated. Astrocyteevoked
electrophysiological responses in neurons were affected by estradiol too. The incidence
and amplitude of the astrocyte-evoked slow inward current in neurons was reduced in presence
of estradiol. Also, acute estradiol treatment decreased the incidence of astrocyte-evoked increase
in spontaneous postsynaptic current frequency in neurons. Astrocyte calcium responses to the
metabotropic glutamate receptor agonist t-ACPD were reduced in presence of estradiol
suggesting functional changes in astrocyte metabotropic glutamate receptors following acute
treatment with estradiol. Our results indicate that glutamate-mediated astrocyte-astrocyte and
astrocyte-neuron communication is sensitive to rapid estradiol-mediated hormonal control.
Disclosures: S.P. Rao, None; S.K. Sikdar, None.
Poster