Chapter 7 – Neurotransmitter release

The neuron is a secretory cell. The secretory product, the neurotransmitter, is released at the level of chemical synapses. Neurotransmitters achieve the transmission of information at the level of chemical synapses between neurons, neurons and muscle cells, neurons and glandular cells, and sensory receptors and neurons. Neurotransmitters synthesized by the neuron are stored in the presynaptic element, inside the synaptic vesicles. In the absence of presynaptic activity, the probability of a neurotransmitter being released in the synaptic cleft is very low. This probability increases strongly when the presynaptic element is depolarized by an action potential. The vesicle hypothesis of neurotransmitter release, first formulated by Del Castillo and Katz (1954), is the generally accepted theory of neurotransmitter release. It states that the neurotransmitter molecules released in the synaptic cleft are those stored in synaptic vesicles. Many recent studies have confirmed the existence of vesicular release, such as data obtained with combined capacitance measurements and amperometry or optical analysis of labeled synaptic vesicles.