AsianScientist (Mar. 9, 2022)– Prolonged isolation from loved ones and loneliness have become a longstanding issue throughout the COVID-19 pandemic, leading to increased stress and mental health issues. Researchers in Japan have reported in Nature Communications that a peptide may be involved with the experience of loneliness and the need for social interaction in female mice.
As with many scientific findings and discoveries, such as the discovery of penicillin, it all started with an interesting observation by Dr Kumi Kuroda and colleagues from the RIKEN Center for Brain Science while they were conducting a different study. The team was initially looking at the effects of amylin, a peptide produced by a specific kind of pancreatic cells, in the medial preoptic area (MPOA) of the forebrain in inducing maternal behavior among female mice. The MPOA is believed to be involved with parental care and behavior in animals such as mice. The researchers used only female mice for the study because the male mice tend to exhibit aggressive behavior toward their cage-mates.
Earlier, the researchers had unintentionally discovered that the amount of amylin present in the female mice was affected by the presence of other females in the housing environment. Eventually, this led to researchers headed by Dr Kansai Fukumitsu, also from RIKEN and collaborator with Kuroda, attempting to understand the association of amylin with loneliness and isolation.
When the researchers isolated some female mice from their cage-mates, they noticed that amylin mRNA in the MPOA area, an indicator of amylin expression, began to decrease in the isolated mice. Prolonged isolation of up to six days led to almost complete obliteration of amylin mRNA in the MPOA. The isolated mice also exhibited behaviors such as vigorous sniffing, digging around and biting the barrier separating them when they could sense the presence of other mice, almost in an attempt to break through and reunite with their cage-mates. The researchers interpreted the behaviors signalling the need for social contact.
The diminished amylin expression in the MPOA did not change even when the isolated mice were given external enrichment such as toys. They also observed that amylin-expressing neurons were inactivated during isolation and activated during reunion.
Baseline amylin presence was restored to normal levels two weeks after the isolated mice were reunited, along with the diminishing of the social contact-seeking behavior. Further experiments using genetically modified mice with knocked down expression of amylin-expressing neurons who were then isolated from their cage-mates revealed that these mice exhibit significantly reduced social contact-seeking behavior. This finding led the researchers to conclude that the absence of amylin may be responsible for behaviors seeking social connection in female mice during isolation.
Social interaction in some mammals such as mice were believed to be the result of the need for collective parenting to ensure the survival of their young. By understanding more about this behavior and the mechanism behind it, the researchers noted it may help understand the physiological effects of loneliness and isolation, which could help with further research in mental health.
“With all these results, we became confident that amylin is the major player in the brain that is needed for sensing and seeking social contacts,” said Kuroda.
The article can be found at Fukumitsu et al. (2022) Amylin-Calcitonin Receptor Signalling in the Medial Preoptic Area Mediates Affiliative Social behaviors in Female Mice.
Source: RIKEN Center for Brain Science; Photo: Unsplash.
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