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Second-order input to the medial amygdala from olfactory sensory neurons expressing the transduction channel TRPM5

John A Thompson1, Ernesto Salcedo, Diego Restrepo

  • 1Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, Aurora, Colorado 80045, USA. john.a.thompson@ucdenver.edu

The Journal of Comparative Neurology
|November 29, 2011
PubMed

Insights

The main olfactory bulb directly influences the medial amygdala via specific mitral cells. These cells target glomeruli expressing TRPM5, crucial for processing social cues like urine odors.

Area of Science:

  • Neuroscience
  • Olfactory System Research
  • Sensory Processing

Background:

  • The main olfactory bulb (MOB) traditionally projects to different brain areas than the accessory olfactory bulb.
  • Recent findings show MOB mitral cells project to the medial amygdala (MeA), a key area for processing social cues.
  • Olfactory sensory neurons (OSNs) expressing TRPM5 are involved in detecting semiochemicals.

Purpose of the Study:

  • To investigate the relationship between MOB-to-MeA projecting mitral cells and TRPM5-expressing glomeruli.
  • To determine if MOB mitral cells targeting the MeA innervate glomeruli associated with TRPM5-expressing OSNs.

Main Methods:

  • Retrograde tracer cholera toxin B (CTB) was injected into the MeA of mice.
  • Mice utilized expressed green fluorescent protein (GFP) under the TRPM5 promoter to label TRPM5-expressing glomeruli.
  • Overlapping CTB-labeled mitral cell dendritic branches and TRPM5-GFP labeled glomeruli were quantified.

Main Results:

  • Significant overlap was observed between CTB-labeled mitral cell dendritic branches and TRPM5-GFP labeled glomeruli.
  • This colocalization occurred at a higher frequency than expected by chance, indicating a specific connection.
  • Some mitral cells projected to non-TRPM5 glomeruli, and some TRPM5 glomeruli received input from non-amygdalopetal cells, showing the connection is not absolute.

Conclusions:

  • A subset of MOB mitral cells projecting to the MeA specifically targets glomeruli innervated by TRPM5-expressing OSNs.
  • This anatomical link supports a direct role for the MOB in processing semiochemicals relevant to social behaviors.
  • The olfactory system exhibits complex, overlapping pathways for processing different types of sensory information.

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