Fifty years ago, the famous science fiction series Doctor Who burst onto the television screens of the world. The show was already on the "bubble" by its third episode and the producers were afraid of cancellation. Then, the show's producer introduced what has become the most fearsome creature in modern science fiction, the Dalek.
How did the Doctor defeat the Daleks in their first appearance? Well it turns out the Daleks slid across a metal floor and their contact with the floor allowed electricity to power their robotic shell. So, the Doctor simply shoved one of the Daleks over onto a nonconducting suface and these fearsome creatures were brought to a sudden halt.
Neurotransmitters function to bridge the gap between the ends of the synapses of two adjacent nerve cells. These foot like appendages reach out from each nerve cell and there is a barely visible gap between them. Like the gap between the Dalek and the floor, if this gap is filled with a nonconducting substance then the flow of electricity stops.
In the brain these gaps contain only fluid and the neurotransmitter has to be squirted into the gap as the electrical impulse arrives to facilitate passage of the nerve impulse from one nerve to another. And so on, down the nerve pathways to the body, these impulses keep us feeling and moving and breathing. So you see, neurotransmitters are absolutely essential to keep one nerve cell in contact with another or you simple grind to a halt. And, that is what we call depression!