Persistent inward currents in rat ventral horn neurones

Area of Science:

• Neuroscience
• Spinal Cord Physiology

Background:

• Interneurones in the mammalian spinal cord display diverse firing patterns.
• These patterns are crucial for motor control and sensory processing.

Purpose of the Study:

• To investigate the role of persistent sodium current in determining ventral horn interneurone firing patterns.
• To classify interneurone firing behaviors and identify the underlying ionic mechanisms.

Main Methods:

• Electrophysiological recordings from rat lumbar spinal cord interneurones.
• Analysis of firing patterns in response to current injection.
• Assessment of persistent inward currents (PICs) using voltage ramps.
• Pharmacological manipulation using riluzole to block persistent sodium current.

Main Results:

• Four distinct interneurone firing patterns were identified: repetitive-firing, repetitive/burst, initial-burst, and single-spiking.
• Repetitive-firing cells exhibited significantly larger PICs.
• Riluzole application converted repetitive and burst firing patterns to single-spiking and reduced PICs.
• Persistent sodium current was identified as the primary contributor to PICs, with a minor role for L-type calcium current.

Conclusions:

• The persistent sodium current is a key determinant of firing patterns in mammalian spinal cord interneurones.
• Understanding these ionic mechanisms provides insight into neuronal excitability and motor control.
• Targeting persistent sodium current may offer therapeutic strategies for neurological disorders affecting spinal cord function.