🔸 Between two neurons lie the pre-synaptic cell and the post-synaptic cell (cells with the synaptic terminal). They are separated by a short distance called the 'synaptic cleft'.
And the molecules of nerve transmitter are going to make their way from pre-synaptic cell to post-synaptic cell through the synaptic cleft.

🔸 Neurotransmitters need to have a termination, if they are not received by the post-synaptic cell. We use three different mechanisms to terminate the message of a neurotransmitter.

1️⃣ Diffusion: The molecules are simply going to diffuse out if they don't make it to the "ears" of post-synaptic terminal of the receiving neuron. So diffusion is a very effective way to terminate a message.

2️⃣ The second way is through something called re-uptake. And re-uptake is typically in the pre-synaptic terminal. There are channels, or transporters, which take neurotransmitters back up. The neurotransmitters get re-packaged and put back into a new vesicles (which are actually recycled as well).

🔸 And this is really important for drugs like #serotonin and #dopamine. And there are drugs that act on the serotonin and dopamine re-uptake transporters that can be used both therapeutically, for instance, to treat depression.

3️⃣ The third way that we terminate a message is through degradation. And in the case of degradation, what we have is enzymes that sit in the synaptic cleft that are just chewing up neurotransmitters. [GIF]

🔸 The molecule that the neurotransmitter where degradation is really important is #acetylcholine.
So, in case of acetylcholine, there is an enzyme that sits between the pre-synaptic and the post-synaptic cells, eating up acetylcholine, called acetylcholinesterase (AChE).

🔸 Acetylcholine is the neurotransmitter that is used by motor neurons. And so, in fact, blocking #acetylcholinesterase can be used for therapeutics — in the case of people that are not releasing enough acetylcholine, or don't have enough receptors for the acetylcholine.

🔸 We can boost the amount of acetylcholine in the cleft by inhibiting the acetylcholinesterase. And that's useful for people with diseases such as myasthenia gravis.