Transmitter‐Induced Calcium Responses Differ in Astrocytes Acutely Isolated from Rat Brain and in Culture

Abstract

Glial fibrillary acid protein (GFAP)-positive astrocytes isolated from the cerebral cortices of 3-10-dayold rats frequently showed increased intracellular Ca 2c oncentration responses to L-glutamate and glutamate analogues. However, few of the acutely isolated cells responded to ATP, and no such cells responded to serotonm [5-hydroxytryptamine(5-HT)]. The same cell that failed to respond to ATP or 5-HT often responded to glutamate. Culturing acutely isolated cells in media containing horse serum decreased Ca2~responses to glutamate but increased the responses to ATP and induced responses to 5-HT. In primary cultures prepared from the cerebral cortices of 1-day-old rats and cultured in horse serum, fewer of the cells responded to glutamate, but almost all cells responded to ATP and 5-HT. The lack of, or limited response to, 5-HT or ATP in the acutely isolated cells seems unlikely to be due to selective damage to the respective receptors because acutely isolated GFAPnegative cells showed responses to ATP, several different proteases and mechanical dissociation yielded cells that also responded to glutamate but not to ATP, and exposure of primary cultures to papain did not abolish Ca2r esponses to several transmitters. The responses of the acutely isolated cells to glutamate but limited or lack of responses to ATP and 5-HT also correspond to what has been seen so far for astrocytes in situ. Thus, the present studies provide direct evidence that some of the receptors seen in primary astrocyte cultures may reflect a response to culture conditions and that, in the context of the relevant information so far available, acutely isolated astrocytes seem to reflect better the in vivo state.

Glia Contribute to the Purinergic Modulation of Inspiratory Rhythm-Generating Networks

“…The P2R sensitivity of glia cultures derived from the VLM and preBötC was therefore instrumental in establishing direct ATP sensitivity of glia. Culturing of cells can induce changes in gene transcription and receptor expression (Kimelberg et al, 1997). However, the properties of glial receptors (including P2Rs) measured in vitro are often unchanged in culture (Neary et al, 1988).…”

Supportive or information-processing functions of the mature protoplasmic astrocyte in the mammalian CNS? A critical appraisal

“…Primary cultures of astrocytes, which provide a seductive experimental simplicity, are not reliable indicators of the properties of astrocytes and how they behave in situ (Kimelberg, 1995;Kimelberg et al, 1997;Kimelberg, 2001;Lovatt et al, 2007;Cahoy et al, 2008). These alternative paths are (1) release by reversal of excitatory amino acid (EAA) transporters, which is only likely to occur under pathological conditions, (2) swelling activated anion channels and also hemi-channels, and (3) P2X receptors for ATP.…”

Astrocyte-Originated ATP Protects Aβ1-42-Induced Impairment of Synaptic Plasticity

“…They do not play a mere structural or metabolic supportive function but rather are active participants in the regulation of neuronal activity in the brain. One of the central functions of astrocytes is the release and uptake of gliotransmitters/neurotransmitters in the neuronal synaptic cleft (Kimelberg et al, 1997). Gliotransmitters are chemicals released from glial cells (Halassa et al, 2007); astrocytes directly activate neuronal receptors by releasing gliotransmitters such as glutamate (Parpura et al, 1994), D-serine (Mothet et al, 2005), and ATP (Coco et al, 2003).…”