Fig 1.
Experimental schedule A: A schedule to elucidate the effects of KSS on SKF-induced social affiliation deficits and grooming behaviors. Five-week-old ICR male mice were divided into 4 groups (I–IV). After a one-week acclimatization period, a three-chamber test, a resident-intruder test, and an open field test were conducted in a one-week period. Each animal group received vehicle + water, 40 mg/kg (i.p.) SKF + water (SKF + water), 74 mg/kg (p.o.) KSS (SKF+Low-KSS), or SKF + 222 mg/kg (p.o.) KSS (SKF+High-KSS) (a–c) before each behavioral test. After completing each test, the animals were returned to their home cages and left with no drug treatment until the next behavioral experiments. Experimental schedule B: A schedule to elucidate the effects of KSS pharmacologically using different receptor antagonists. The three-chamber test and open field test were conducted using 6-week-old and 8-week-old male mice, respectively. The animals received the test drug treatment according to the order indicated, and social affiliation behaviors and grooming behaviors were elucidated by a three-chamber test and an open field test, respectively. The animals were used only once in each behavioral experiment.
Fig 2.
Effects of KSS on SKF-induced social deficits in male mice.
The sociability-related performance of mice was analyzed by measuring social affiliation behaviors in the three-chamber test (A) and social interaction behaviors in the resident-intruder tests (B). A: Summarized data on social affiliation performance (i) and locomotor activities (ii) of each animal group in the test trials of the three-chamber test. The preference of each animal group for the stranger chamber was expressed as a discrimination index calculated according to the equation described in the text. Locomotor activity of each animal group in the test trial was measured using the Smart system. B: Social interactions between the drug-treated resident and naïve control animals. The total duration of the time the drug-treated resident mouse spent sniffing the intruder mouse was measured as an index of social interaction during a 10-min observation period. Vehicle or SKF (40 mg/kg, i.p.) was administered 3 hr before the behavioral test. SKF-treated animals were orally administered water or KSS [74 mg/kg (Low-KSS) and 222 mg/kg (High-KSS)] 1 hr before the test. Each data column represents the mean ± S.E.M. The numbers of animals used are indicated in each parenthesis. *P < 0.05, **P < 0.01 vs. the corresponding vehicle group. #P < 0.05 vs. SKF+water group.
Fig 3.
Effects of KSS on anxiety-related behaviors (A) and repetitive grooming behaviors (B) in SKF-treated mice. A) Anxiety-like behaviors of each mouse group were analyzed as the percentage of time spent in the center zone in the open field during the first 10-min observation period. B) The total cumulative duration of each mouse spent for self-grooming was measured during the latter 10-min observation period between 5 and 15 min after starting the open field test. KSS was administered orally at doses of 74 mg/kg (Low-KSS) and 222 mg/kg (High-KSS) 1 h before the test. Each data column represents the mean ± S.E.M. The numbers of animals used are indicated in each parenthesis. **P < 0.01 vs. the corresponding vehicle group. #P < 0.05 vs. SKF+water group.
Fig 4.
Effects of KSS on SKF-induced decrease in endogenous ALLO content in the frontal cortex.
After completing the open field test conducted according to experimental schedule A (Fig 1), each animal was decapitated, and the frontal cortices were dissected for neurochemical studies. ALLO content in the frontal cortex was measured using ELISA. Each data column represents the mean ± S.E.M., and the numbers of animals used are indicated in each parenthesis. *P < 0.05 vs. the corresponding vehicle group.
Fig 5.
Pharmacological analysis of the ameliorative effects of KSS on SKF-induced social deficits in male mice.
Preference for the stranger chamber was expressed as a discrimination index and used as an index of sociability-related performance in mice. A discrimination index was calculated according to the equation described in the text. Experiments 1 and 2 were conducted using different animal groups. Antagonists [SCH23390 (SCH: 0.2 mg/kg), sulpiride (SUL: 5 mg/kg), bicuculline (BIC: 1 mg/kg), phaclofen (PHA: 2 mg/kg)] were injected intraperitoneally 30 min before the test. Each data column represents the mean ± S.E.M., and the numbers of animals used are indicated in each parenthesis. **P < 0.01 vs. the corresponding vehicle group. #P < 0.05 vs. SKF+High-KSS group.
Fig 6.
Pharmacological analysis of the ameliorative effects of KSS on SKF-induced repetitive self-grooming behaviors in male mice.
Time each animal spent for repetitive self-grooming was measured in an open field test. Experiments 1 and 2 were conducted using different animal groups. Antagonists [SCH23390 (SCH: 0.2 mg/kg), sulpiride (SUL: 5 mg/kg), bicuculline (BIC: 1 mg/kg), phaclofen (PHA: 2 mg/kg)] were injected intraperitoneally 30 min before the test. Each data column represents the mean ± S.E.M., and the numbers of animals used are indicated in each parenthesis. *P < 0.05, **P < 0.01 vs. the corresponding vehicle group. #P < 0.05 vs. SKF+High-KSS group.