Exploratory and agile behaviors with central dopaminergic activities in open field tests in Formosan wood mice (Apodemus semotus)

Abstract

Taiwan is a mountainous island, and nearly 75% of its lands are 1000 m above sea level. Formosan wood mice, Apodemus semotus, are endemic rodents and are broadly distributed at altitudes between 1400 and 3700 m in Taiwan. Interestingly, Formosan wood mice show similar locomotor activity in the laboratory as they do in the wild. Hence, we are interested in studying whether exploratory behaviors and central dopaminergic activity are changed in the open field test. We used male C57BL/6J mice as the control, comparing their behavioral responses in the open field, step-down inhibitory avoidance discrimination and novel object recognition tests with those of male Formosan wood mice. We also examined dopamine and its major metabolite 3,4dihydroxyphenylacetic acid in the medial prefrontal cortex, striatum and nucleus accumbens. In open field tests, Formosan wood mice revealed higher levels of locomotion and exploration than C57BL/6J mice. Learning and memory performance in the novel object recognition test was similar in both Formosan wood mice and C57BL/6J mice, but more agile responses in the inhibitory avoidance discrimination task were found in Formosan wood mice. There was no difference in behavioral responses in the open field test between new second-generation Formosan wood mice and Formosan wood mice that were inbred for more than 10 generations. After repeated exposure to the open field test, high levels of locomotion and exploration as well as central dopaminergic activities were markedly persistent in Formosan wood mice, but these activities were significantly reduced in C57BL/6J mice. Diazepam (anxiolytic) treatment reduced the higher exploratory activity and central dopaminergic activities in Formosan wood mice, but this treatment had no effect in C57BL/6J mice. This study provides comparative findings, as two phylogenetically related species showed differences in behavioral responses.

Regular fecal microbiota transplantation to Senescence Accelerated Mouse-Prone 8 (SAMP8) mice delayed the aging of locomotor and exploration ability by rejuvenating the gut microbiota

“…The open field tests were performed in reference to the previous study ( Larke et al, 2017 ; Shieh and Yang, 2019 , 2020 ) on 7, 9, and 11°months old of SAMP8 mice. The apparatus was consisted of a 45 × 45 × 45°cm chamber with the bottom painted black and the surroundings left transparent and one circular object was put in the center of the chamber.…”

Lytic Cell Death in Specific Microglial Subsets Is Required for Preventing Atypical Behavior in Mice

“…Mice were individually placed in the center of a platform (5 x 5 cm) of a maze that consisted of two open and two closed arms (30 x 5 cm) that were elevated 30 cm from the floor. Mice were allowed to freely explore the maze for 10 min (Lin and Hsueh, 2014;Nakajima et al, 2019;Shieh and Yang, 2019) and the Smart Video Tracking System (Panlab) was used to determine the time spent in the open and closed arms, as well as the center, during the test. The number of entries into each arm was also analyzed.…”