Astrocyte Protocol

Astrocytes in Neurotransmitter function in the recycling of Glutamate and GABA and prevent over excitability

Glutamatergic neurons (which produce glutamate) release glutamate across the synaptic gap. This glutamate binds to receptors on the next neuron, allowing positive ions to flow in, triggering that neuron to activate. After this, the glutamate needs to detach from the receptor to avoid overstimulating the neuron.

To prevent this excess activity, special transporter proteins recycle the glutamate back into the original neuron, where it's stored for future use. However, if these transporters become overloaded, glutamate can remain in the gap and continue to stimulate neighboring neurons.

Astrocytes, a type of support cell in the brain, can help manage this by absorbing extra glutamate. They convert it into glutamine, which is a more stable form, through an enzyme called glutamine synthetase. The astrocytes then release the glutamine back to the original neuron, which can convert it back into glutamate using another enzyme (glutaminase) and store it for reuse.

GABAergic neurons, which produce GABA (a calming neurotransmitter), can also regulate this process. GABA is actually made from glutamate. When there's too much GABA in the synaptic gap, it can be turned into glutamine, transported back into the original neuron, and then reconverted into glutamate. That glutamate can then be changed back into GABA, ensuring the neuron has a fresh supply of GABA ready to release.

 

Glial cells, Astrocytes – CNS only, part of the BBB

Glial cells are the supportive cells of the nervous system. Unlike neurons, which transmit signals, glial cells provide essential support functions such as maintaining homeostasis, protecting neurons, and helping with repair and waste removal. Types of glial cells include astrocytes, microglia, oligodendrocytes, and Schwann cells, each playing a role in insulating neurons, managing inflammation, and regulating the environment around nerve cells to ensure proper brain and spinal cord function.

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Astrocytes in respect to the blood brain barrier (BBB)

BBB is 3 layers

1. Inner: Endothelial cells bound together by tight junctions to control permeability

2. middle: Basal lamina – connective tissue (protein)

3. outside: Astrocytes with foot processes.  Astocytes secrete molecules/growth factors that stimulate the endothelial cells to make more tight junctions which increases permeability. As astrocytes malfunction, tight junction production decreases allowing unwanted increased permeability in the BBB.

 

Pericytes are also involved

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Astrocytes and the blood-brain barrier (BBB):

The BBB controls what moves between the blood and nervous tissue, but some areas in the brain don’t have a BBB to help monitor the blood:

1. Area postrema (near the medulla): This area lacks a BBB so the brain can detect toxins and trigger vomiting to remove them.

2. Osmoreceptors near the hypothalamus: These check blood for salt, sugar, or water imbalances and signal the body to drink more or less, or adjust urination via ADH from the pituitary.

3. Between the hypothalamus and pituitary: This open area allows hormones from the hypothalamus to reach the pituitary.

 

Astrocytes help control potassium levels around neurons. Too much potassium in a neuron makes it more excitable. Astrocytes "mop up" excess potassium to prevent overstimulation. When neurons send signals, sodium rushes in and potassium exits through channels. Astrocytes store excess potassium in the space around neurons, helping maintain balance. They also help redistribute potassium between themselves and neurons to prevent overexcitability, ensuring proper function.​