Voltage-gated currents, dye and electrical coupling in the embryonic mouse neocortex.

Area of Science:

• Neuroscience
• Developmental Biology
• Electrophysiology

Background:

• Cellular communication and electrical properties are crucial for brain development.
• Understanding ion channel expression patterns provides insights into neuronal maturation and migration.

Purpose of the Study:

• To investigate the expression and distribution of voltage-gated currents in different zones of the embryonic mouse sensorimotor cortex.
• To correlate ion channel properties with cellular events like cell cycle exit and migration.

Main Methods:

• Whole-cell voltage clamp recordings were performed on slices of mouse sensorimotor cortex at embryonic day 14 (E14).
• Dye coupling and electrical coupling were measured to assess cell-to-cell communication.
• Delayed potassium currents (I(K)) and inward sodium currents (I(Na)) were characterized in ventricular zone (VZ), intermediate zone (IZ), and cortical plate (CP) cells.

Main Results:

• VZ cells showed extensive dye coupling but limited electrical coupling, facilitating accurate current measurements.
• All VZ cells expressed I(K); 30% also expressed I(Na), suggesting early cell cycle exit.
• IZ and CP cells exhibited varying I(Na) amplitudes, with CP cells showing significantly larger currents than VZ cells.
• No hyperpolarization-activated currents were detected in any zone.

Conclusions:

• The distribution and amplitude of I(Na) differ across cortical layers during development.
• I(Na) expression patterns may serve as a marker for early neuronal differentiation, cell cycle exit, and migration.