Endogenous brain-derived neurotrophic factor triggers fast calcium transients at synapses in developing dendrites

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Brain-derived neurotrophic factor (BDNF) plays a critical role in neuronal development and network formation.
• The precise spatiotemporal characteristics of intrinsic BDNF signaling remain largely unknown.
• Understanding BDNF signaling is key to deciphering neuronal development and function.

Purpose of the Study:

• To directly observe and characterize the intrinsic spatiotemporal dynamics of BDNF signaling in developing hippocampal neurons.
• To investigate the role of BDNF in regulating calcium transients at subcellular and synaptic levels.
• To elucidate the molecular mechanisms underlying BDNF-mediated calcium signaling.

Main Methods:

• Utilized calcium imaging to monitor intrinsic BDNF signaling in developing hippocampal neurons.
• Employed function-blocking BDNF antibodies (alphaBDNF) and K252-a to inhibit BDNF signaling.
• Used focal BDNF application and virus-mediated expression of PSD-95:CFP to study signaling events.

Main Results:

• Blocking intrinsic BDNF signaling reduced spontaneous, localized calcium rises in dendrites.
• Focal BDNF application induced fast, localized dendritic calcium transients requiring TrkB receptor activation and ion channels.
• Spontaneous calcium transients frequently occurred at postsynaptic sites and were specifically reduced by blocking BDNF signaling.

Conclusions:

• BDNF-dependent calcium signaling in developing hippocampal neurons is rapid and synapse-specific.
• These spatiotemporal characteristics make BDNF a critical molecule for establishing synaptic connectivity.
• BDNF signaling is essential for the formation of functional neuronal networks.