Behavioural NeuroscienceResearch PaperThe vomeronasal organ is required for the male mouse medial amygdala response to chemical-communication signals, as assessed by immediate early gene expression
Section snippets
Animals
Forty eight (Exp. 1) and 24 (Exp. 2) sexually naive 3–4 month old male C57 BL/6 mice (Jackson Laboratory) were maintained on a reverse 12/12 h light/dark cycle with food and water ad libitum. All animal procedures were approved by the Florida State University Institutional Animal Care and Use Committee. Animals had no contact with any heterospecific stimuli before the experimental session, no contact with females or female stimuli since weaning and no contact with the male or female conspecific
Results
Exposure to mMU, fMU or CC stimuli, all representatives of behaviorally salient stimuli, increased IEG expression in both MeA and MeP in sham-operated (SHAM) male mice. HVF, selected as a representative non-salient stimulus, increased IEG expression in MeA, but not MeP of SHAM mice. These expression patterns confirm our previous findings, using intact mice, of the characteristic and categorical difference between medial amygdala response to biologically relevant and to non-relevant stimuli (
Discussion
In this report, we provide evidence that IEG response to biologically relevant chemical signals in the medial amygdala depends on an intact VNO. We have previously reported that the pattern of IEG expression in medial amygdala to biologically relevant (mainly conspecific) chemical signals is categorically different from the pattern of most heterospecific stimuli. These non-relevant heterospecific chemosensory stimuli do elicit an amygdala response, but have little or no effect on behavior and
Acknowledgments
This work was supported by National Institute on Deafness and Other Communication Disorders grants dc 005813 and T32 DC00044 (M.M.) and fellowship F31 DC08062 (C.L.S.).
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