Action potential-induced dendritic calcium dynamics correlated with synaptic plasticity in developing hippocampal...

Area of Science:

• Neuroscience
• Developmental Biology
• Calcium Signaling

Background:

• Intracellular calcium increases are crucial for long-term potentiation (LTP) in hippocampal CA1 pyramidal cells.
• LTP magnitude develops during postnatal weeks 2-3 in rats, but calcium dynamics during this period are poorly understood.

Purpose of the Study:

• To investigate the postnatal development of intracellular calcium dynamics in CA1 pyramidal cell dendrites.
• To correlate calcium dynamics with the maturation of synaptic plasticity during early development.

Main Methods:

• Whole-cell patch-clamp recordings and calcium imaging using fura-2 in rat hippocampal CA1 pyramidal cells.
• Measurement of dendritic calcium increases evoked by action potentials and depolarization under voltage-clamp.
• Application of cadmium chloride (CdCl2) to block voltage-dependent calcium channels (VDCCs).
• Utilizing theta-burst stimulation (TBS) to assess calcium responses during LTP induction protocols.

Main Results:

• Dendritic calcium increases evoked by action potentials were minimal in the first postnatal week, becoming 3-6 fold larger by weeks 2-3.
• High-threshold VDCCs mediate enhanced calcium influx, evidenced by larger calcium currents and dendritic calcium accumulation at later developmental stages (P15-18 vs. P4-7).
• Theta-burst stimulation induced robust intracellular calcium increases in later developmental stages, coinciding with the maturation of LTP.

Conclusions:

• Developmental enhancement of action potential-evoked intracellular calcium increases in hippocampal neurons is observed.
• Maturation of high-threshold voltage-dependent calcium channel activity contributes to increased calcium influx during development.
• Strengthened calcium signaling likely underlies the maturation of calcium-dependent functions, including synaptic plasticity, in developing hippocampal neurons.