Abstract
Gentle touch contributes to affiliative interactions. We investigated the effects of gentle stroking in female rats on the development of affiliative behaviors toward humans and we exploratively examined brain regions in which activity was influenced by stroking. Rats that had received stroking stimuli repeatedly after weaning emitted 50-kHz calls, an index of positive emotion, and showed affiliative behaviors toward the experimenter. Hypothalamic paraventricular oxytocin neurons were activated in the rats after stroking. The septohypothalamic nucleus (SHy) in the post-weaningly stroked rats showed decreased activity in response to stroking stimuli compared with that in the non-stroked control group. There were negative correlations of neural activity in hypothalamic regions including the SHy with the number of 50-kHz calls. These findings revealed that post-weaning stroking induces an affiliative relationship between female rats and humans, possibly via activation of oxytocin neurons and suppression of the activity of hypothalamic neurons.
Highlights
IntroductionThere were negative correlations of neural activity in hypothalamic regions including the septohypothalamic nucleus (SHy) with the number of 50-kHz calls
Post-weaning stroking stimuli for more than 4 weeks facilitated the emission of 50-kHz calls, induced preference and affiliative behavior toward the experimenter’s hand, increased reward values in stroking stimuli, and induced activation of oxytocin neurons in the caudal paraventricular nucleus (PVN) after stroking in female rats as reported in male rats
The present study further demonstrated that post-weaning stroking stimuli decreased the activity of several brain regions, the septohypothalamic nucleus (SHy), and increased activity in cortical regions including the insular cortex
Summary
There were negative correlations of neural activity in hypothalamic regions including the SHy with the number of 50-kHz calls These findings revealed that post-weaning stroking induces an affiliative relationship between female rats and humans, possibly via activation of oxytocin neurons and suppression of the activity of hypothalamic neurons. We previously found that gentle tactile stimulation during a post-weaning period induced emission of 50-kHz calls and resulted in the development of intimate relationships between humans and male rats possibly via activation of hypothalamic oxytocin neurons[28]. Female rats vocalize 50-kHz calls less frequently than male rats do in response to tickling stimuli given by humans[25].
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