Neurotransmission

      The brain is made up of millions of cells. The cells in the brain that are affected by MDMA are called neurons. Neurons are very important because they allow certain regions of the brain to interact with one another. A very helpful model when imagining the neurons in the brain is the Internet. The internet allows many different people in many different regions of the world to interact. People are like neurons, and reigons of the globe are like regions of the brain which consist of millions of neurons. Regions of the globe (like regions of the brain) can converse via the internet, but this depends on the individual connections between the people (like neurons).

      Unlike other cells, which are often quite round and evenly shaped, neurons are usually shaped like trees with an owl's hole in the middle. The owl's hole would be where the cell body is located, and from there the dendrites branch out like the top of a tree and the single axon travels out like the trunk. The dendrites receive information from other neurons and pass it down to the cell body where the information is processed. This information is then passed along through the neuronís trunk or axon. At the end of the axon you find the roots of the neuron. The roots, or terminal branches, extend to where they can directly pass messages to the dendrites of other neurons. Such messages are passed from the little round knobs at the end of the axon called terminal buttons. Chemical messages leave the terminal buttons and go into the synaptic gap between the terminal buttons of one neuron and the dendrites of another neuron. Once in the synaptic gap, the chemical messengers float around until they connect to the dendrites of the other neurons. The relay of a message from one neuron to another is called neurotransmission.

      The message that is transmitted through the neurons is an electrical impulse which is produced when neurons are stimulated. When the electrical impulse reaches the terminal buttons, at the end of the axon, it causes the release of neurotransmitters. The neurotransmitters travel across the synapse and relay the information to the next axon. Scientists have spent a lot of time trying to find all of the different neurotransmitters in the brain and figure out just what kinds of messages each one usually delivers.

      When trying to understand how neurotransmitters work, think of the sending of a message from the terminal buttons of one neuron and the reception of the message in the dendrite of another. The neuron that is sending the message from its terminal buttons is called the presynaptic neuron. The receiving neuron in this exchange is called the postsynaptic neuron. During neurotransmission, a neurotransmitter must be released from the terminal button of the presynaptic neuron, cross the synaptic gap and attach to the postsynaptic neuron. This process is not as simple as it might sound.

      Neurotransmitters are produced in the cell body of neurons and then carried through the cell down the axon to the terminal buttons. Here, the neurotransmitters are stored in vesicles until electrical changes within the cell cause these vesicles to release them into the synaptic gap. In order for the neurotransmitter to reach the postsynaptic neuron and relay the information in the brain, the neurotransmitter must be released into the synaptic gap. The postsynaptic neuron, however, is rather hard of hearing, and it needs many neurotransmitters to attach to it before it can hear the message that the presynaptic neuron is sending. Luckily, each vesicle contains many copies of its specific neurotransmitter, so the chances that enough neurotransmitters will successfully cross the synaptic gap and attach to the postsynaptic neuron are high, as long as enough vesicles release their cargo at once.

      When a neurotransmitter attaches to the postsynaptic neuron specific changes take place that depend on which neurotransmitter is involved. Some neurotransmitters cause channels to open up in the postsynaptic axon that then allow ions that are floating around outside the cell to enter it. Depending on which ions and how many are involved, they can cause an electrical impulse to travel down the axon. When this electrical impulse, called an action potential, is produced in the postsynaptic neuron, it will travel through the neuron (its axon, cell body, and dendrite) and begin the whole process of neurotransmission again.

      As you can see, neurotransmission is a complex process. Hopefully this explanation has illustrated it well enough that you will be able to understand how neurons are affected by MDMA. There is one other aspect of neurotransmission, however, that is important to consider when discussing the effects of drugs like MDMA. What happens to neurotransmitters after they have finished passing the action potential on to the postsynaptic neuron? This stage is called reuptake. Reuptake is fairly specific, depending on which neurotransmitter is being discussed. Basically, neurotransmitters must either be taken back up into the cell that released them or be broken down by an enzyme secreted by the postsynaptic membrane.


Introduction

Neurotransmission

Neurotransmitters

Dopamine

Serotonin


Main Table of Contents