Chemosensory and steroid-responsive regions of the medial amygdala regulate distinct aspects of opposite-sex odor preference in male Syrian hamsters

In rodent species, such as the Syrian hamster, the expression of sexual preference requires neural integration of social chemosensory signals and steroid hormone cues. Although anatomical data suggest that separate pathways within the nervous system process these two signals, the functional signific...

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Bibliographic Details
Published in:The European journal of neuroscience 2006-12, Vol.24 (12), p.3541-3552
Main Authors: Maras, Pamela M., Petrulis, Aras
Format: Article
Language:English
Subjects:
Amygdala - anatomy & histology
Amygdala - physiology
Analysis of Variance
Animals
Behavior, Animal
Cricetinae
Discrimination, Psychological - physiology
Functional Laterality
lesions
Male
Mesocricetus
Odorants
olfaction
Radioimmunoassay - methods
reproductive behavior
Sex Characteristics
Sexual Behavior, Animal - physiology
sexual preference
Steroids - blood
Time Factors
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Summary:In rodent species, such as the Syrian hamster, the expression of sexual preference requires neural integration of social chemosensory signals and steroid hormone cues. Although anatomical data suggest that separate pathways within the nervous system process these two signals, the functional significance of this separation is not well understood. Specifically, within the medial amygdala, the anterior region (MEa) receives input from the olfactory bulbs and other chemosensory areas, whereas the posterodorsal region (MEpd) contains a dense population of steroid receptors and receives less substantial chemosensory input. Consequently, the MEa may subserve a primarily discriminative function, whereas the MEpd may mediate the permissive effects of sex steroids on sexual preference. To test these hypotheses, we measured preference and attraction to female and male odors in males with lesions of either the MEa or MEpd. In Experiment 1, lesions of either region eliminated opposite‐sex odor preferences. Importantly, MEpd‐lesioned males displayed decreased attraction toward female odors, suggesting decreased sexual motivation. In contrast, MEa‐lesioned males displayed high levels of investigation of both male and female odors, suggesting an inability to categorize the relevance of the odor stimuli. In Experiment 2, we verified that both MEa‐ and MEpd‐lesioned males could discriminate between female and male odors, thereby eliminating the possibility that the observed lack of preference reflected a sensory deficit. Taken together, these results suggest that both the MEa and MEpd are critical for the expression of opposite‐sex odor preference, although they appear to mediate distinct aspects of this behavior.
ISSN:0953-816X
1460-9568
DOI:10.1111/j.1460-9568.2006.05216.x