Cerebral blood flow & metabolism

Synaptic astrocytes
1. regulate synaptic transmission by
- responding to ATP and glutamate,
released from the presynaptic neuron
- uptake of glutamate from the synaptic
cleft via membrane transporters (green
arrow) or the release of glutamate upon
reversal of the transporter induced by 
[Na+]i
- D-serine released from astrocyte
strengthen synaptic transmission by
coactivating NMDA receptors in the
postsynaptic membrane, or reduce
synaptic transmission by secreting
transmitter-binding proteins (TBP
2. communicate with adjacent astrocytes
via gap junctions and with distant
astrocytes via extracellular ATP.
3. the rise in Ca2+ causes release of
glutamate from astrocytes, and ATP is
released via an unknown mechanism,
which propagates ATP signaling to
An electron micrograph of a synapse surrounded adjacent cells.
by an astrocyte (yellow) from the spinal cord of rat
From Fields and Stevens-Graham, 2005
GluR, glutamate receptor; Ado, adenosine; IP3,
inositol trisphosphate; P1, adenosine
receptor; P2, ATP receptor.
Comunicare neuro-gliala – “unda de calciu” in retele gliale
Calcium imaging reveals communication between neurons and glia. (A) Molecules
released during synaptic transmission bind receptors on glia that cause increases
in intracellular Ca2+ (rainbow colored cells), which are propagated as waves
through glial networks. (B) Increases or decreases in axonal firing may coincide
with the passage of a glial Ca2+ wave. Oligodendrocytes (purple) myelinate CNS
axons. Vm, membrane voltage.
From Fields and Stevens-Graham, 2005