The plasticity of neuronal synapses—that is, the dynamic relationship between two neurons in the brain as one sends signals to another—ultimately underlies cognition, learning, and memory. The increase in synaptic strength following a burst of stimulation, dubbed post-tetanic potentiation (PTP), is driven by an increase in the amount of neurotransmitter ready to be released from the presynaptic side, and it’s the most important form of plasticity in so-called mossy fiber synapses in the hippocampus. A new study finds this potentiation can be regulated by the postsynaptic cell by sending the neurotransmitter glutamate back to the presynaptic side—a form of retrograde signaling that neuroscientists hadn’t anticipated existed in this synapse.
Infographic: Reverse Signaling Between Neurons
So-called mossy fiber synapses in the hippocampus can meter the amount of neurotransmitter they receive by sending glutamate against the usual direction of synaptic flow.


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Christie Wilcox, PhD
Christie is a seasoned science journalist and cell and molecular biology PhD; her debut book Venomous: How Earth’s Deadliest Creatures Mastered Biochemistry, received widespread acclaim. She was a member of The Scientist’s editorial team from 2021–2023.View full profile