Parvalbumin expression reveals a vibrissa-related pattern in rabbit SI cortex

Area of Science:

• Neuroscience
• Comparative Anatomy
• Cortical Circuitry

Background:

• Parvalbumin-like immunoreactivity (PV-LIR) is a marker for specific neuronal populations.
• The primary somatosensory cortex (SI) processes sensory information, including whisker input.
• Rodent SI cortex exhibits a distinct barrel architecture for whisker representation.

Purpose of the Study:

• To investigate the expression pattern of PV-LIR in the rabbit SI cortex's vibrissae representation.
• To compare PV-LIR distribution in rabbits with known patterns in rodents.
• To understand how PV-LIR relates to cortical organization in lagomorphs.

Main Methods:

• Immunohistochemical examination of PV-LIR in postnatal day 21 and adult rabbit SI cortex.
• Analysis of PV-LIR distribution in different cortical layers (IV, V, VI).
• Correlation of PV-LIR patterns with cytoarchitectural features and neuronal cell types.

Main Results:

• PV-LIR formed distinct vibrissa-like patches in layer IV, despite indistinct barrels.
• Patches contained dense PV-LIR terminals and concentrated labeled stellate neurons.
• Basket cells and pyramidal cells in deeper layers also showed specific PV-LIR patterns.
• PV-LIR in upper layer VI aligned with the vibrissae pattern and included labeled non-pyramidal and modified pyramidal cells.

Conclusions:

• PV-LIR in rabbits delineates cortical modules comprising thalamocortical afferents and local inhibitory circuits.
• The absence of distinct barrels but presence of PV-LIR patches suggests an alternative organizational principle in rabbits.
• Differences in PV-LIR patterns between rabbits and rats may reflect species-specific adaptations in whisker processing circuits.