Male and female odors induce Fos expression in chemically defined neuronal population

Area of Science:

• Neuroscience
• Olfactory System
• Behavioral Biology

Background:

• Olfactory information significantly influences innate and social behaviors in rodents.
• The medial nucleus of the amygdala (MEA) and ventral premammillary nucleus (PMV) are known to be activated by conspecific odors.
• The specific neuronal populations within these regions responding to odors remain largely unidentified.

Purpose of the Study:

• To identify the neurochemical identities of neurons in the MEA and PMV activated by conspecific odors.
• To investigate sex-specific odor responses in these brain regions.
• To understand the role of specific neuronal markers (NADPHd, urocortin 3, GAD-67) in olfactory processing.

Main Methods:

• Exposure of male rats to female or male odors.
• Assessment of Fos immunoreactivity (Fos-ir) to indicate neuronal activation.
• Colocalization analysis of Fos-ir with markers for NADPH diaphorase activity (NADPHd), urocortin 3, and GAD-67 mRNA in the MEA and PMV.

Main Results:

• Both male and female odors induced Fos-ir in the MEA and PMV, with a higher response to female odors.
• In the MEA, NADPHd neurons showed Fos-ir only with female odors, while urocortin 3 neurons did not activate.
• GAD-67 mRNA was coexpressed in a significant portion of activated MEA neurons (80% for male odors, 50% for female odors).
• PMV neurons showed intense NADPHd activity, with NADPHd/CART neurons responding to both male and female odors.

Conclusions:

• Female and male odors activate distinct neuronal populations in the MEA, suggesting a basis for context-specific behavioral responses to olfactory cues.
• NADPHd/CART neurons in the PMV respond to both male and female odors, indicating a role in olfactory-mediated neuroendocrine regulation.