During which phase is the choline remnant taken up by the neuron?

The choline remnant is taken up by the neuron during the recycling phase. In synaptic transmission involving cholinergic neurons, acetylcholine (ACh) is released into the synaptic cleft, where it binds to receptors on the post-synaptic neuron. After this action, ACh is broken down by the enzyme acetylcholinesterase into choline and acetate.

The choline portion is then recycled by being actively transported back into the presynaptic neuron. This uptake of choline allows the neuron to synthesize new acetylcholine for subsequent neurotransmission. By effectively recycling choline, neurons maintain their supply of neurotransmitter, therefore facilitating continued communication across synapses.