Dynamic modulation of phasic and asynchronous glutamate release in hippocampal synapses

Area of Science:

• Neuroscience
• Cell Biology
• Synaptic Transmission

Background:

• Short-term presynaptic plasticity modulates neurotransmitter release.
• Asynchronous release, distinct from synchronous release, is prominent during repetitive stimulation and linked to residual calcium.
• Mechanisms selectively controlling asynchronous release remain underexplored.

Purpose of the Study:

• Investigate the role of protein kinase C (PKC) in modulating synchronous versus asynchronous neurotransmitter release.
• Determine if phorbol ester (PDBu) differentially affects phasic and asynchronous release.
• Elucidate the contribution of PKC-dependent and -independent pathways to these effects.

Main Methods:

• Utilized cultured excitatory autaptic hippocampal neurons.
• Applied phorbol ester (PDBu) to modulate presynaptic release.
• Examined the effects of PDBu and PKC inhibition on phasic and asynchronous release during action potential trains.
• Quantified changes in evoked neurotransmitter release.

Main Results:

• PDBu treatment increased both phasic and asynchronous neurotransmitter release.
• PKC inhibition had minor effects on PDBu-potentiated phasic release.
• PKC inhibition significantly reduced PDBu-potentiated asynchronous release, particularly late in stimulus trains.

Conclusions:

• PKC plays a critical role in potentiating asynchronous neurotransmitter release.
• Distinct PKC-dependent and -independent mechanisms may control synchronous and asynchronous release.
• Findings suggest differential regulation of vesicle fusion events at the synapse.