London: Two new studies have discovered surprising details about the complex process that leads to the flow of neurotransmitters between brain neurons -- a dance of chemical messages so delicate that missteps often lead to neurological dysfunction.
A recent study led by Timothy Ryan, professor of biochemistry at Weill Cornell Medical College, demonstrated that individual neurons somehow control the speed by which they recycle synaptic vesicles that store neurotransmitters before they are released.
No one had expected that neurons would have such a powerful “gas pedal,” said Ryan.
Ryan is also contributing author of a second, Yale University–led study, which shows that the common understanding about how proteins help form these key storage vesicles is flawed.
Both studies focus on synaptic vesicles, which are bubble-like structures that store neurotransmitters within a bi-layer of fatty membranes at the synaptic junction.
“We are looking under the hood of these machines for the first time. Many neurological diseases such as Alzheimer’s disease, Parkinson’s disease, schizophrenia and other neurodegenerative and psychiatric disorders are considered to be synaptopathies -- pathologies of synaptic function. So repairing them will require that we understand how they work,” Ryan explained.
In the first study, they discovered that an individual neuron retrieves all of its synaptic vesicles at pretty much the same speed.
They also found that while each cell had its own speed at recovering the vesicles, that rate varied four-fold across the different neurons -- even if the neurons were performing identical functions, such as secreting the same neurotransmitter.
“When we compared different neurons, we found that each cell is telling its synapses to go at its own speed. The mystery that remains is the nature of this gas pedal, and if it might be important in therapeutic approaches to tackling synaptopathies,” he said.
The second study looked at what happened when both dynamin 1 and dynamin 3, which makes up 99 percent of dynamin protein, are missing.
“Our studies showed that retrieval is now severely impaired when you have neither dynamin 1 nor dynamin 3, which shows us that dynamin 3 has a major presynaptic function,” added Ryan.
The studies were published in Nature Neuroscience and in the online edition of Neuron.