Problem

A researcher is interested in uncovering mechanisms of synaptic transmission between two neurons. To do this, she is studying neurons cultured from embryonic mouse brain neural cells. The researcher is interested in several aspects of neurotransmission between neurons, but is particularly focused on the role of the synapse in transmitting neuronal signals. Using the cultured system, she is able to examine individual pairs of neurons that communicate through chemical synapses, and modify different aspects of the synaptic environment. She can decrease the extracellular concentration of various ions and observe how this affects neurotransmitter release and target cell behavior. She can also apply a toxin that prevents synaptic vesicles from fusing with the presynaptic membrane of axon terminals. Prior to these manipulations, the researcher does a control experiment with two neurons where she stimulates the presynaptic neuron to fire an action potential and measures the response of the postsynaptic neuron. Consistently, the postsynaptic neuron depolarizes and propagates an excitatory potential.
Where are neurotransmitters stored prior to release at a synapse?
Please choose from one of the following options.
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