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A Neurohypophysial End Game: Spreading Excitation With Sildenafil.

Armstrong WE

University of Tennessee Health Sciences Center.

Neurotransmitter release is a function of the pattern and frequency of propagated action potentials arriving at the axon terminal, and central nervous system (CNS) synapses can exhibit a variety of forms of synaptic plasticity in response to this activity. Seminal studies at the frog neuromuscular junction and giant squid synapse revealed that the clustering of action potentials transiently facilitates transmitter release, primarily through enhanced Ca++ signaling. This is evident at many mammalian synapses as well, but understanding the full complement of mechanisms that successfully code arriving action potentials been hindered due to the small size of most CNS terminals (often ~1 microm), which makes direct recordings difficult even with the advanced forms of optical guidance that characterize modern neurophysiology. A notable exception is the Calyx of Held in the auditory system, a large terminal that can be recorded simultaneously with its postsynaptic partner.

Published 24 August 2007 in J Physiol.
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