Glial cells... the most common type of cell in the nervous system.
Glia comes from the Greek word for glue. Glial cells act as nervous system adhesives, keeping everything together and working properly. They are non-excitable cells, which obviously means they do not produce action potentials. This, in my opinion, is why neurons get all the attention, even though glial cells outnumber nerve cells many magnitudes over.
You'll find several types of Glia in the CNS.
1. Oligodendrocytes (Schwann Cells in the PNS) act to sheath axons with myelin.
2. Microglia, the guardians of the brain, are activated during an infection and after damage. They are kind of like the janitors, cleaning up the mess.
3. Astrocytes are the most common glial cells. If I remember correctly, they make up 90% of all glial cells.
* I mentioned Schwann Cells briefly. They can be myelinating or non-myelinating. The non-myelinating type sits around the NMJ, providing necessary trophic support, regulating the function of the synapse.
Microglia:
These guys are the resident immune cells. They are immediately activated post-injury, and are therefore hyperactive during neurodegenerative disorders. Researchers think they may play a role in development as well.
Oligodendrocytes:
These are the myelinating cells. They originate from the same stem cells as astrocytes and are implicated in demyelinating diseases such as MS. Myelin proteins are known inhibitors of axon regeneration.
Astrocytes:
Astrocytes allow us to have a glialcentric view of the nervous system as well as a neurocentric one. What do astrocytes do during neural development, exactly? Just a few of the findings are as follows:
* RGCs can be cultured in the absence and presence of glia
* Glia increase synaptic activity
* Soluble signals released by astrocytes induce an increase in synapse numbers on RGCs
*Purified thrombospondin is sufficient to increase synapse numbers to the ACM levels
* TSP 1 and 2 expression is developmentally regulated.
So what are Thrombospondins?
They are proteins with antiangiogenic (inhibits the growth of new blood vessels) abilities. The acronym is TSP. TSP 1 and 2 are expressed by developing astrocytes, with TSP4 being expressed at the NMJ. They regulate cell attachment, the cytoskeleton, migration, and of course angiogenesis.
But most importantly, they are synaptogenic, meaning they induce synapse formation. Synaptogenic function is mediated through an EGF-like domain. The drug Gabapentin specifically blocks synapse formation induced by TSP, by the way. Drugs like this (Neurontin and Lyrica) are used to treat chronic pain and epilepsy, but their actual mechanism of action is unknown. I'm pretty sure they were developed with the intention of blocking the Ca2+ channel subunit that acts as the receptor for Gabapentin & Pregabalin (*note the GABA theme here) but didn't end up doing the specific molecular action that the scientists initially desired (isn't this how basically every drug is developed, as a failure turned multi-billion dollar miracle pill? read...Viagra).
Glia comes from the Greek word for glue. Glial cells act as nervous system adhesives, keeping everything together and working properly. They are non-excitable cells, which obviously means they do not produce action potentials. This, in my opinion, is why neurons get all the attention, even though glial cells outnumber nerve cells many magnitudes over.
You'll find several types of Glia in the CNS.
1. Oligodendrocytes (Schwann Cells in the PNS) act to sheath axons with myelin.2. Microglia, the guardians of the brain, are activated during an infection and after damage. They are kind of like the janitors, cleaning up the mess.
3. Astrocytes are the most common glial cells. If I remember correctly, they make up 90% of all glial cells.
* I mentioned Schwann Cells briefly. They can be myelinating or non-myelinating. The non-myelinating type sits around the NMJ, providing necessary trophic support, regulating the function of the synapse.
Microglia:
These guys are the resident immune cells. They are immediately activated post-injury, and are therefore hyperactive during neurodegenerative disorders. Researchers think they may play a role in development as well.
Oligodendrocytes:
These are the myelinating cells. They originate from the same stem cells as astrocytes and are implicated in demyelinating diseases such as MS. Myelin proteins are known inhibitors of axon regeneration.
Astrocytes:
Astrocytes allow us to have a glialcentric view of the nervous system as well as a neurocentric one. What do astrocytes do during neural development, exactly? Just a few of the findings are as follows:
* RGCs can be cultured in the absence and presence of glia
* Glia increase synaptic activity
* Soluble signals released by astrocytes induce an increase in synapse numbers on RGCs*Purified thrombospondin is sufficient to increase synapse numbers to the ACM levels
* TSP 1 and 2 expression is developmentally regulated.
So what are Thrombospondins?
They are proteins with antiangiogenic (inhibits the growth of new blood vessels) abilities. The acronym is TSP. TSP 1 and 2 are expressed by developing astrocytes, with TSP4 being expressed at the NMJ. They regulate cell attachment, the cytoskeleton, migration, and of course angiogenesis.
But most importantly, they are synaptogenic, meaning they induce synapse formation. Synaptogenic function is mediated through an EGF-like domain. The drug Gabapentin specifically blocks synapse formation induced by TSP, by the way. Drugs like this (Neurontin and Lyrica) are used to treat chronic pain and epilepsy, but their actual mechanism of action is unknown. I'm pretty sure they were developed with the intention of blocking the Ca2+ channel subunit that acts as the receptor for Gabapentin & Pregabalin (*note the GABA theme here) but didn't end up doing the specific molecular action that the scientists initially desired (isn't this how basically every drug is developed, as a failure turned multi-billion dollar miracle pill? read...Viagra). 
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