It has been documented that both histaminergic and GABAergic systems participate in the neurobiology of anxiety behaviour. In the current research, we investigated the effects of the histaminergic system and GABA A receptor agents on anxietyrelated behaviours and their interaction using the elevated plus maze test in mice.Intraperitoneal (I.P.) administration of muscimol (0.12 and 0.25 mg/kg) increased the open arm time (OAT) (P < 0.001) without affecting the open arm entries (OAE) and locomotor activity, showing an anxiolytic effect. I.P. injection of bicuculline (0.5 and 1 mg/kg) decreased OAT (P < 0.001) but not OAE and locomotor activity, suggesting an anxiogenic behaviour. Intracerebroventricular (I.C.V.) microinjection of histamine (2.5 and 5 μg/mouse) resulted in a decline in OAT (P < 0.001) but not OAE and locomotor activity, indicating an anxiogenic response. Co-administration of histamine with GABAergic agents, muscimol (0.06 mg/kg; I.P.) and bicuculline (0.25 mg/kg; I.P.), decreased (P < 0.001) and increased (P < 0.05), respectively, the anxiogeniclike response to the effective dose (5 μg/mouse; I.C.V.) of histamine. In addition, cotreatment of effective doses of histamine (2.5 and 5 μg/mouse;I.C.V.) with an effective dose of muscimol (0.12 mg/kg; I.P.) and a non-effective dose of bicuculline (0.25 mg/kg; I.P.) significantly decreased OAT (P < 0.001), suggesting a likely interaction between the histaminergic and GABAergic systems in the regulation of anxiety. The results demonstrated a synergistic anxiogenic-like effect between histamine and bicuculline in mice. In conclusion, our results present an interaction between the histaminergic and GABAergic systems in anxiolytic/anxiogenic-like behaviours in the elevated plus maze test.

We investigated the effects of histamine and GABAA receptor agents on pain and depression-like behaviors and their interaction using a tail-flick test and the forced swimming test (FST) in male mice. Our data revealed that intraperitoneal administration of muscimol (0.12 and 0.25 mg/kg) increased the percentage of maximum possible effect (%MPE) and area under the curve (AUC) of %MPE, indicating an antinociceptive response. Intraperitoneal injection of bicuculline (0.5 and 1 mg/kg) decreased %MPE and AUC of %MPE, suggesting hyperalgesia. Moreover, muscimol by reducing the immobility time of the FST elicited an antidepressant-like response but bicuculline by enhancing the immobility time of the FST caused a depressant-like response. Intracerebroventricular (i.c.v.) microinjection of histamine (5 µg/mouse) enhanced %MPE and AUC of %MPE. i.c.v. infusion of histamine (2.5 and 5 µg/mouse) decreased immobility time in the FST. Co-administration of different doses of histamine along with a sub-threshold dose of muscimol potentiated antinociceptive and antidepressant-like responses produced by histamine. Cotreatment of different doses of histamine plus a noneffective dose of bicuculline reversed antinociception and antidepressant-like effects elicited by histamine. Cotreatment of histamine, muscimol, and bicuculline reversed antinociceptive and antidepressant-like behaviors induced by the drugs. The results demonstrated additive antinociceptive and antidepressant-like effects between histamine and muscimol in mice. In conclusion, our results indicated an interaction between the histaminergic and GABAergic systems in the modulation of pain and depression-like behaviors.

Background: Mental health is a significant problem in developed and developing countries which influences all aspects of life. We aimed to evaluate the status of Iranian students' mental health. Methods: This cross-sectional study was performed on 2052 elementary school students located in Tehran, Iran, in September 2018. We used the Census sampling method for sampling and the general health questionnaire comprising 28 items. For statistical analysis SPSS software, version 21 was used. Results: A total of 2052 elementary school students (1373 girls and 679 boys) participated in this study. The mean ± standard deviation (SD) ages of the girls and boys were 14.1±1.7 and 13.9±1.1 years, respectively. The mean ± SD of anxiety, social dysfunction, and depression scores were 7.42±4.92, 7.35±3.33, 6.83±2.26 in the girls and 5.65±3.89, 6.30±3.09, 4.61±1.74 in the boys, respectively. The mean ± SD total scores in boys and girls were 20.48±12.31 and 27.90±14.66, respectively. Conclusion:The mental health status of elementary school students was generally low, especially in male students.