Add to playlist
The video was prepared for inclusion in a full length documentary titled 'The Dark Gene', produced by FilmTank, and directed by Miriam Jakobs and Gerhard Schick.
We have created the animation of the serotoninergic synapse, trying to interpret in visual terms the knowledge available about this very specific neural site. The scene set (the synapse) is an environment delimited by the two membranes of the opposing neurons and includes the space defined by the presence of synaptic proteins anchored into the membranes. This space is filled with an aqueous solution (water not shown), in which are dissolved many small molecules: some which are ubiquitous in our body (glucose and ions) and some other which are more characteristic of the brain extracellular environment (some neurotransmitters like GABA and Glutamate). We should notice that even if the synapse works in one direction, and even if we have placed the upstream neuron above the receiving one, at the scale of nanometer, and with the very small masses involved, the notion of up and down does not really make much sense: we have tried to encode this information in the initial minute of the animation, when the synaptic space is seen rotating. When the signal arrives form the body of the upstream neuron (shown as a series of lightnings, accompanied by a specific sound), the presynapse get organized to release the content of one of its vescicles: many thousands of serotonin molecules are poured into the synaptic cleft, and float around like confetti in a box.
Given the small space of the synapse, quite immediately they are sensed by the receptors in the post-synapse: one of them, the ionotropic receptor (or 5-HT3), responds primarily by opening the channel to let ions go through (thus depolarizing the membrane and so propagating the electric signal), while another, the metabotropic receptor, has the primary function of transmitting the signal to the interior of the cell. A mechanism of transmitter reuptake is also immediately activated in the presynaptic neuron: the aptly called reuptake receptors, located at the periphery of the synapse, avidly ‘eat’ as many serotonin molecules as they can, bringing them back into the upstream neuron, and making them available for recycling. In the cases of depression due to low serotonin, the pharmacological inhibition of these reuptake receptors can help by letting more of the neurotransmitter lingering in the synaptic space (and probably also beyond). Among the most effective of the inhibitors is a drug known as Prozac®, which shares some chemical features with serotonin itself. When the reuptake receptor ‘eats’ a fluoxetine molecule, the drug sticks into the entrance and impedes further reuptake. With higher level of serotonin in the brain, several depressed patients are able to restore the ‘normal’ mood, and are relieved from the condition. We have represented this ‘return to normality’ as a brighter light in the synapse of the treated brain.
