Type: dissertation
Abstract: Introduction. Social cognitive functions are regulated on neural circuits among brain regions such as prefrontal cortex (PFC), hippocampus, amygdala, and others. Furthermore, the neuropeptide oxytocin involved in social cognitive functions. In this study, we examine the neural mechanisms of social cognitive functions in rodents, focusing on the relationship between social memory and the PFC. Study 1. We examined the role of the PFC subregions, the prelimbic cortex (PL) and anterior cingulate cortex (ACC), in short-term social memory, social motivation, and anxiety-related behaviors in male mice. The PL or ACC lesioned group, as well as those in a sham control group, underwent the social recognition test and social novelty test where juvenile and adult male mice were used as social stimuli, the open field test and light-dark transition test. In the social recognition test, the PL-lesioned mice exhibited habituation but not dishabituation regardless of whether juvenile or adult mice were used as social stimuli. ACC lesions didn’t affect habituation and dishabituation. In the social novelty test, PL-but not ACC-lesioned mice spent less time engaged in social investigation compared with the control mice when adult mice were used as social stimuli. These results suggest that PL lesions impaired both social recognition and social motivation. Furthermore, PL lesions and ACC lesions did not affect general activity in the open field test and anxiety-related behavior in the light-dark transition test. We newly found the PL but not the ACC plays an important role in short-term social recognition and social motivation. Study 2.We examined the role of oxytocin receptors in the PFC on short- and long-term social memory. We injected an oxytocin receptor antagonist (OTA) into the PFC in male mice. The mice were divided into the high-dose OTA, low-dose OTA and vehicle control group (artificial cerebrospinal fluid: aCSF). All grouped mice underwent the social recognition test, the open field test, and the light/dark transition test 15 min after each drug injection. The social recognition test was conducted three trials of 5 min each on 3 consecutive days (total of 9 trials). In the social recognition test, the control group showed exhibited short-term habituation each day. In contrast, the OTA-H group showed impairment in short-term habituation on the 2nd and the 3rd days, and the OTA-L group showed impairment in short-term habituation on only the 3rd day. Each group did not show long-term habituation. Furthermore, the effects of OTA injection did not affect general activity in the open field test and anxiety-related behavior in the light-dark transition test. In the present study, we found that injection of OTA into the PFC dose-dependently impaired short-term social memory. Our findings demonstrated that oxytocin receptors in the PFC played important roles in short-term social memory. Discussion. We provided a perspective on the neural network of social cognitive functions centered on the PFC, based on previous studies and our two studies. Although the neural networks involved in social cognitive functions are unclear, the PFC-amygdala-hippocampal circuit might play an essential role in social memory and social motivation. In this neural circuit, the PFC might perform top-down processing; thus, it is necessary to continue to examine the neural basis of social cognitive functions with a focus on the PFC. In addition, social memory has not been studied systematically due to the small number of studies. Therefore, it is expected that their various functions and mechanisms will be studied in more detail.
Author: 八島, 成維
Language: Japanese
Subfield: Endocrine and Autonomic Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7144834291