Astrocytes in 17β-estradiol treated mixed hippocampal cultures show attenuated calcium response to neuronal activity

• Published in: Glia Vol. 53; no. 8; pp. 817 - 826
• Main Authors: Rao, Shilpa P., Sikdar, S.K.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.06.2006; Wiley-Liss
• Subjects: Biological and medical sciences; calcium wave; fluo-3 AM; Fundamental and applied biological sciences. Psychology; Isolated neuron and nerve. Neuroglia; metabotropic glutamate receptors; neuron-astrocyte signaling; Vertebrates: nervous system and sense organs; Glial cell; Calcium; Neuroglia; Central nervous system; neuron-astrocyte signaling; 17β-Estradiol; metabotropic glutamate receptors; Glutamate receptor; Astrocyte; Encephalon; Signal transduction; calcium wave; fluo-3 AM; Neuron; Metabotropic receptor; Hippocampus
• ISSN: 0894-1491; 1098-1136
• DOI: 10.1002/glia.20341

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 ([Ca2+]i). Using simultaneous electrophysiology and calcium imaging techniques, we monitored neuronal activity evoked astrocyte ([Ca2+]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 ([Ca2+]i) elevations in astrocytes, which could be blocked by 200 μM MCPG and also 1 μM TTX. We compared astrocytic ([Ca2+]i) transients in control and 24‐hour estradiol treated cultures. The amplitude of the ([Ca2+]i) transient, the number of responsive astrocytes, and the ([Ca2+]i) wave velocity were all significantly reduced in estradiol treated cultures. ([Ca2+]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 ([Ca2+]i) response seen following estradiol treatment could have functional consequences on astrocyte‐neuron signaling. © 2006 Wiley‐Liss, Inc.