Effect of Post-Weaning Individual Housing on Autonomic Responses in Male Rats
to Sexually Receptive Female Rats |
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Authors: | Hideaki Inagaki Masayoshi Kuwahara Hirokazu Tsubone |
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Institution: | Department of Comparative Pathophysiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan |
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Abstract: | Post-weaning individual housing induces significant alterations in the reward system of
adult male rats presented with sexually receptive female rats. In this study, we examined
the effects of post-weaning individual housing on autonomic nervous activity in adult male
rats during encounters with sexually receptive female rats to assess whether different
affective states depending on post-weaning housing conditions are produced. Changes in
heart rate and spectral parameters of heart rate variability indicated that in
post-weaning individually housed male rats, both sympathetic and parasympathetic activity
increased with no change in the sympathovagal balance, while in post-weaning socially
housed male rats, both sympathetic and parasympathetic activity decreased with a
predominance of parasympathetic activity. These two patterns of shifts in sympathovagal
balances closely resembled changes in autonomic nervous activity with regard to classical
appetitive conditioning in male rats. The autonomic changes in male rats housed
individually after weaning corresponded to changes associated with the reward-expecting
state evoked by the conditioned stimulus, and the autonomic changes observed in male rats
housed socially after weaning corresponded to changes associated with the reward-receiving
state evoked by the unconditioned stimulus. These results suggest that different affective
states were induced in adult male rats during sexual encounters depending on male–male
social interactions after weaning. The remarkable change caused by post-weaning individual
housing may be ascribed to alteration of the reward system during sexual encounters
induced by deficiency of intermale social communication after weaning. |
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Keywords: | early social isolation positive affective state power spectral analysis of heart rate variability social communication |
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