Question

You get a brain slice and perfuse it with distilled water containing 0.9% NaCl, 0.09% KCl, and an innocuous pH buffer. You patch onto two neurons that have chemical synapses connecting them, but you see no response in the post-synaptic cell when you stimulate the pre-synaptic cell. However, when you stimulate each cell individually, you observe action potentials only within the stimulated cell. What did you forgot to include in your perfusion solution?

Answer 1

For the transmission of neural stimulation across the synapse , which is a chemical synapse here , the release of a neurotransmitter is needed .

The neurotransmitter is synthesized within the presynaptic neuron and packed into small vesicles which then move towards the presynaptic membrane to be fused with it and be released into the synaptic cleft .

For the movement of the synaptic vesicles towards the presynaptic membrane calcium is needed which is taken in from the surrounding environment via voltage gated calcium channels .

The given perfusion solution is missing calcium ions in it and hence the impulse cannot be transmitted across the synapse but the individual neurons can be excited , due to the failure of the synaptic vesicles to migrate to the presynaptic membrane .

Hope this answers your question.