Gap junctions between CA3 pyramidal cells contribute to network synchronization in neonatal hippocampus

Area of Science:

• Neuroscience
• Developmental Biology
• Cellular Electrophysiology

Background:

• Direct electrical coupling through gap junctions provides crucial intercellular connectivity during neural development when synaptic connections are limited.
• Existing pharmacological tools for studying gap junctions often lack specificity, hindering functional investigations.

Purpose of the Study:

• To investigate gap-junctional coupling between CA3 pyramidal cells in the neonatal hippocampus.
• To determine the contribution of this electrical coupling to early network activity generation.

Main Methods:

• Utilized four different gap junction inhibitors, including carbenoxolone, in P3-6 rat hippocampal slices.
• Recorded network activity bursts and evoked spikelets in CA3 pyramidal cells.
• Assessed the effects of inhibitors on synaptic transmission and action potential firing patterns.

Main Results:

• General gap junction blockers, like carbenoxolone, reduced the frequency of network activity bursts in the CA3 hippocampal area.
• Carbenoxolone inhibited spikelets evoked by local stimulation, indicating axo-axonic gap junction connectivity, independent of chemical synaptic transmission.
• Carbenoxolone decreased the success rate of antidromic action potential firing and altered spontaneous action potential firing patterns.

Conclusions:

• Electrical coupling between CA3 pyramidal cells plays a significant role in generating early network events in the neonatal hippocampus.
• Gap junction-mediated electrical coupling modulates neuronal firing patterns and synchronization, contributing to the establishment of neural circuits.
• These findings highlight the importance of electrical synapses in early brain development and network formation.