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Astrocytes in 17β‐estradiol treated mixed hippocampal cultures show attenuated calcium response to neuronal activity
Author(s) -
Rao Shilpa P.,
Sikdar S.K.
Publication year - 2006
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.20341
Subject(s) - astrocyte , biology , glutamate receptor , metabotropic glutamate receptor , hippocampal formation , endocrinology , depolarization , medicine , neurotransmission , neuroscience , neuron , neuroglia , agonist , receptor , central nervous system , biochemistry
Glial cells in the brain are capable of responding to hormonal signals. The ovarian steroid hormone 17β‐estradiol, in addition to its actions on neurons, can directly affect glial cells. Estrogen receptors have been described on both neurons and astrocytes, suggesting a complex interplay between these two in mediating the effects of the hormone. Astrocytes sense and respond to neuronal activity with a rise in intracellular calcium concentration ([Ca 2+ ] i ). Using simultaneous electrophysiology and calcium imaging techniques, we monitored neuronal activity evoked astrocyte ([Ca 2+ ] i ) changes in mixed hippocampal cultures loaded with fluo‐3 AM. Action potential firing in neurons, elicited by injecting depolarizing current pulses, was associated with ([Ca 2+ ] i ) elevations in astrocytes, which could be blocked by 200 μM MCPG and also 1 μM TTX. We compared astrocytic ([Ca 2+ ] i ) transients in control and 24‐hour estradiol treated cultures. The amplitude of the ([Ca 2+ ] i ) transient, the number of responsive astrocytes, and the ([Ca 2+ ] i ) wave velocity were all significantly reduced in estradiol treated cultures. ([Ca 2+ ] i ) rise in astrocytes in response to local application of the metabotropic glutamate receptor (mGluR) agonist t‐ACPD was attenuated in estradiol treated cultures, suggesting functional changes in the astrocyte mGluR following 24‐h treatment with estradiol. Since astrocytes can modulate synaptic transmission by release of glutamate, the attenuated ([Ca 2+ ] i ) response seen following estradiol treatment could have functional consequences on astrocyte‐neuron signaling. © 2006 Wiley‐Liss, Inc.