The posteromedial cortical amygdala regulates copulatory behavior, but not sexual odor preference, in the male Syrian hamster (Mesocricetus auratus)

doi:10.1016/j.neuroscience.2008.08.004

Neuroscience

Volume 156, Issue 3, 15 October 2008, Pages 425-435

https://doi.org/10.1016/j.neuroscience.2008.08.004 Get rights and content

Abstract

In rodent species, the expression of reproductive behavior relies heavily on the perception of social odors, as well as the presence of circulating steroid hormones. In the Syrian hamster, chemosensory and hormonal cues are processed within an interconnected network of ventral forebrain nuclei that regulates many aspects of social behavior. Within this network, the posteromedial cortical amygdala (PMCo) receives direct projections from the accessory olfactory bulbs and contains a dense population of steroid receptor-containing neurons. Consequently, the PMCo may be important for generating odor-guided aspects of reproductive behavior, yet little is known regarding the role of this nucleus in regulating these behaviors. Thus, the present study tested male hamsters with site-specific electrolytic lesions of the PMCo for their (a) sexual odor preference in a Y-maze apparatus, (b) sexual odor discrimination in a habituation-dishabituation task, and (c) copulatory behavior when paired with a sexually receptive female. PMCo-lesioned males preferred to investigate female odors over male odors and were able to discriminate between these odor sources. However, PMCo lesions were associated with several alterations in the male copulatory pattern. First, PMCo-lesioned males displayed increased investigation of the female's non-anogenital region, suggesting that the PMCo may be involved in directing appropriate chemosensory investigation during mating. Second, PMCo lesions altered the temporal pattern of the mating sequence, as PMCo-lesioned males took longer than Sham-lesioned males to reach sexual satiety, as indicated by the delayed expression of long intromissions. This delayed onset of satiety was associated with an increased number of ejaculations compared with Sham-lesioned males. Importantly, these data provide the first direct evidence for a functional role of the PMCo in regulating male reproductive behavior.

Section snippets

Subjects

All animals in this study were Syrian hamsters (Mesocricetus auratus) purchased from Charles River Laboratory (Wilmington, MA, USA) at 3 weeks of age and singly-housed until the age of behavioral testing (3–6 months). Subjects were sexually naïve males that had been gonadectomized and implanted s.c. with testosterone Silastic capsules prior to lesion surgery (see below). Ovariectomized, hormone-primed female hamsters served as stimulus animals for the copulatory behavior tests (see below). A

Lesion verification

Males were included in the PMCoX lesion group (n=11) only if they had extensive bilateral damage of the PMCo. Specifically, all males in the PMCoX group had at least 50% bilateral damage that included the middle three sections of the PMCo (Fig. 2). In four of these males, damage extended into the rostral sections of the PMCo, whereas in seven subjects, damage extended into caudal PMCo. However, there were no differences in either the preference or copulatory behavior between males with rostral

Discussion

The present results demonstrate that the PMCo regulates two distinct aspects of the mating sequence in male Syrian hamsters. First, the PMCo may be involved in directing appropriate chemosensory investigation during mating, as males with lesions of the PMCo displayed increased investigation of the female's non-anogenital region compared with SHAM males. Second, the PMCo may regulate sexual satiety, as PMCo-lesioned males took longer than SHAM males to display long intromissions, an indication

Conclusions

The present study provides the first direct evidence for a functional role of the PMCo in regulating male reproductive behavior. Specifically, the PMCo regulates two distinct aspects of male copulatory behavior in the Syrian hamster: directing chemosensory investigation of the female and regulating the onset of sexual satiety. Importantly, the PMCo is part of an interconnected network of ventral forebrain nuclei that regulate many aspects of rodent social behavior (Wood, 1997). We hypothesize

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Behavioural neuroscienceThe posteromedial cortical amygdala regulates copulatory behavior, but not sexual odor preference, in the male Syrian hamster (Mesocricetus auratus)

Abstract

Section snippets

Subjects

Lesion verification

Discussion

Conclusions

Horm Behav

Physiol Behav

Horm Behav

Anim Behav

Brain Res

Behav Neural Biol

Brain Res

Physiol Behav

Behav Biol

Behav Neural Biol

Physiol Behav

Neurosci Lett

Neuroscience

Physiol Behav

Behav Brain Res

Physiol Behav

J Steroid Biochem Mol Biol

Pharmacol Biochem Behav

Brain Res

Horm Behav

Physiol Behav

Horm Behav

Horm Behav

Horm Behav

Physiol Behav

Behav Brain Res

Horm Behav

Physiol Behav

Brain Res Bull

Brain Res

Horm Behav

Brain Res

Neuroscience

Behavioural neuroscience
The posteromedial cortical amygdala regulates copulatory behavior, but not sexual odor preference, in the male Syrian hamster (Mesocricetus auratus)