The Journal of Neuroscience, 1999, 19:RC32:1-6
RAPID COMMUNICATION
Functional Dichotomy within the Vomeronasal System: Distinct
Zones of Neuronal Activity in the Accessory Olfactory Bulb Correlate
with Sex-Specific Behaviors
Arvind
Kumar,
Carol A.
Dudley, and
Robert L.
Moss
University of Texas Southwestern Medical Center at Dallas,
Department of Physiology, Dallas, Texas 75235-9040
Chemosensory neurons in the vomeronasal organ (VNO) detect
pheromones that elicit social and reproductive behaviors in most terrestrial vertebrates. Vomeronasal receptor neurons are
chemoarchitecturally divided into two populations based on their
position in the VNO, the type of G-protein subunit expressed, the
family of putative pheromone receptor expressed, and termination site
of their axons in the accessory olfactory bulb (AOB). To investigate
the functional implications of these two segregated VNO-AOB pathways,
we stimulated mice with pheromonal cues associated with different
behavioral contexts and examined cellular activation patterns in the
AOB. Exposure of ICR male mice to BALB/c males resulted in aggressive behavior, accompanied by a VNO-dependent increase in c-fos
immunoreactivity in a cluster of cells located almost exclusively in
the caudal AOB in both strains. This caudal cluster of activated cells
did not appear to require the overt display of aggressive behavior because it was present in both the dominant and submissive males and
could be evoked when the stimulus animal was anesthetized. In contrast,
exposure of an ICR male to an ICR female in diestrus resulted in
activation of cells located predominantly in the rostral AOB. Our
findings indicate that male-to-male interactions involving interstrain
recognition activate a separate population of vomeronasal receptor
neurons than chemosensory cues detected in a sexual context. The
results suggest that the dichotomy in the peripheral vomeronasal system
serves to separate pheromones based on the behaviors they drive. As
such, the results provide a bioassay for identifying pheromone molecules.
Key words:
vomeronasal organ; accessory olfactory bulb; pheromones; sex-specific behaviors; c-fos immunoreactivity; mice
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