Evidence for Ca(2+)-permeable AMPA receptors in the olfactory bulb

Area of Science:

• Neuroscience
• Olfactory System Research
• Molecular Neurobiology

Background:

• alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPARs) are crucial for olfactory bulb (OB) processing.
• AMPARs composed of different subunits exhibit varied properties, including calcium permeability (CP-AMPARs).
• Increased intracellular calcium can modulate odor-encoding mechanisms.

Purpose of the Study:

• To investigate the presence and function of calcium-permeable AMPARs (CP-AMPARs) in rat OB neurons.
• To determine if CP-AMPARs contribute to synaptic transmission and odor encoding in the OB.

Main Methods:

• Whole-cell recording in OB cultures and slices.
• Histological and immunocytochemical (ICC) techniques.
• Application of selective CP-AMPAR antagonist (NAS) and other pharmacological agents (AP5, spermine).
• Cobalt (Co(2+)) staining to assess CP-AMPAR function.

Main Results:

• NAS inhibited AMPAR-mediated currents in subsets of OB interneurons and principal cells.
• Spermine application induced inwardly rectifying currents in some neurons.
• Olfactory nerve stimulation evoked excitatory responses suppressed by NAS, indicating functional CP-AMPARs at synapses.
• Co(2+) staining and ICC revealed diverse expression patterns of CP-AMPARs and GluR2 subunits.

Conclusions:

• Subsets of rat OB neurons express functional CP-AMPARs, including at synapses.
• Calcium influx through CP-AMPARs in the OB may play a significant role in modulating neuronal activity and odor encoding.
• CP-AMPARs could influence downstream signaling pathways, affecting K+ channels, NMDA receptors, and Ca(2+)-binding proteins.